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AKARI Observer`s Manual for the Post-Helium (Phase 3) - RSSD

1. a Ns 4 C SMP83 lower resolution As in the previous example the target list comprises of a unique I D in ascending but not necessarily contiguous order followed by some identifier for the target name which in the case of many of our targets should resolvable the NED SIMBAD systems The IRCZ4 AOT has 2 parameters to set the filter set and the slit position The filter set is determined by whether we wish to use the NP filter set a or NG filter set b element of the NIR camera A tool iris_sky is provided to aid us with the positioning of the instruments over our fields With it we can project our instrument arrays onto our target fields on images from IRAS and 2MASS With iris sky it is also possible to create our target list in its entirety although we shall construct ours manually in this case The use of iris sky has been decribed in Version 3 2 of the Observers manual including an example in the cookbook iris sky has been modified for Phase 3 of the AKARI mission The FIS and IRC MIR information has been removed from the Target list editing panel and messages amended accordingly Only the IRC NIR detector is shown on the display by default other detectors can be switched on via the options panel Detector positions are updated from the nominal position in the Observer s Manual to be relatively consistent with the images We can use the iris_sky tool to visualize our observations and Figure 1 3 1
2. W and Micro Scan operations M They are optimized such that the maximum exposure time is obtained The AOTS are designed to use more than 600 sec in the case that extra observation time is available The actual observation time depends on the stability of the target acquisition procedure Maneuver A AA EN iS EDE AO E Figure 4 4 6 Observation sequences of the AOT IRCZO Z2 Z3 and Z4 Yellow boxes indicated as exposure cycle with filter dispersion element names are exposure cycles Orange boxes with M are Micro Scan operations including stabilization and light blue boxes with W are Filter Wheel rotations Dead time for a Filter Wheel change depends on the relative position of the elements The Green area on the right side is the extra observation time which is not guaranteed Note that for IRCZ2 filter 2 corresponds to NP when parameter b is specified Version 1 1 June 12 2008 39 4 4 1 Detection Limits and Saturation Limits General Remarks In the following sections the expected detection limits for corresponding AOTs are given These are 50 detection limits per single pointing opportunity extrapolated from the performance evaluated in phase 2 for relatively low background sky high ecliptic latitude regions with the assumption that the detection limit
3. 20 AKARI Observer s Manual Control On Board AOCS FSTS IRC Scan ADS Sensors Data Data Realtime one day ISAS I wd f ESA y 1 2 weeks Pointing All Sky Survey Reconstruction Data Reduction 5 in scan On fly 7 cross scan Catalogue ia After Phase 2 Pointing All Sky Survey a Reconstruction Data Reduction 3 in scan AKARI 5 cross scan Catalogues Figure 3 2 2 The outline of the AKA RI attitude determination for the All Sky Survey including time scales and envisioned accuracy improvement Note that the pointing reconstruction by ESA is not carried out for the pointed observations Slewing maneuver to point the telescope at the target position Stabilization of the telescope Observation of the target Returning to the survey mode Ae OO ND The total operation is completed in 30 minutes This means that the maximum number of pointed observations per orbit is three if and when we can find a suitable set of targets separated by 120 deg The actual net observation time per pointing is however limited to 10 minutes To increase the flexibility of the observation opportunity for any target the telescope can point at any position on the sky in a stripe of 2 degree 1 deg perpendicular to the nominal scan path However this allowance is much smaller than previous missions such as IRAS ISO and Spitzer Observers ha
4. ation more severely than plotted in these figures Figure 4 4 9 shows the 50 detection limits for diffuse sources with the Ns slit with NP and NG in low sky background regions assuming that the slit width and the FWHM of the PSF given in Table 4 2 4 For the Nh slit the detection limit becomes larger by a factor of 5 3 100 A Ss 5 NP ei NG E E 10 4 lt o N A ME oe gt t gt Y a D LO a EE 1045 5 Es 3 35 4 4 Wavelength um Figure 4 4 8 50 detection limits for point sources with NP or NG in IRCZ4 100 aaam 5o Detection Limit MJy sr llocs 1 1 ae 25 4 45 5 55 3 35 Wavelength um Figure 4 4 9 50 detection limits for diffuse sources with NP or NG in IRCZ4 Version 1 1 June 12 2008 49 Saturation Limits The saturation limits for NP and NG are about 3 and 10Jy respectively However the saturation in the N3 imaging data sandwiched by spectroscopic observations could make it difficult to determine the reference wavelength position accurately for observations with Nc and Np The saturation level for N3 is given in Table 4 4 6 50 AKARI Observer s Manual 4 5 Notes and Restrictions for the IRC Observations 1 Bright sources Bright sources that saturate the NIR detectors will not leave significant effects on the following observations and thus will be planned not to be prohibited However bright sources in the FoV can produce unwanted array anomalies
5. In general the preparation of Open Time proposals follows the algorithm below using dedi cated tools available via a web interface In addition we expect users to iterate their observations using the tools before their final submission in order to obtain the best possible observation strategy Note that the tools available for Phase 3 Open Time are a scaled down and limited data set compared to those available in the earlier call In particular the Instrument Performance Tool IPT is not available for Phase 3 observation planning 1 Target selection and visibility check 2 Preparation of the Target list 3 Validation check of the Target list 4 Run Duplication Check Tool 5 Submission via Submission Tool 53 54 AKARI Observer s Manual A 2 Example 1 Spectroscopy of distant galaxies with the NG grism in the point source aperture In this worked example we consider a program to carry out spectroscopy using the AKARI IRC NG high resolution grism in the 1x1 arcmin point source aperture We will simulate the preparation of the proposal from scientific background to proposal submission A 2 1 Scientific Background The advent of the SCUBA instrument on the JCMT Hawaii allowed mapping of the sub millimetre Universe for the first time The first surveys detected a new population of dusty starburst galaxies the high redshift analogue of local ULIRGs Hughes et al 1998 Smail et al 1997 Subsequent surveys have incre
6. Observation with this mode can be made in regions of moderate to high visibility which allow two or more pointed observations at each target position Description In this mode the IRC dispersion elements are used to take spectra of the targets The wavelength coverage of the NP moderate resolution and NG high resolution are similar to each other and the user should choose one of these two for this AOT As we explain in section 4 1 5 a slit is provided in each camera in order to observe diffuse radiation The NIR camera also has an entrance aperture slit for a point source to enable confusion less spectroscopy It is used with the NG in high resolution mode see below In phase 3 all the combinations of the slit selection are available both for NP and NG An image with N3 is taken for pointing alignment No dithering operation is carried out during one pointing in this AOT Observers are highly recommended to observe the same area of the sky on two or more independent orbits to ensure data redundancy If the multiple observations with Np or Nh are requested under the same target 1D small shift along the slit among independent pointing observations are arranged automatically in the scheduling software Observers who wish to set the observation positions by themselves should specify the target position in each pointing opportunity and should not use multiple pointing assignments Parameters The first parameter specifies the dispersion e
7. such as mux bleed and thus should be avoided as much as possible Some constraint for observing fields with very bright sources may be given for IRC observations as observations progress 2 Effects of South Atlantic Anomaly SAA Passage through the SAA does not cause serious damage to the detectors However detector performance may be significantly degraded immediately after the SAA Current observation scheduling allocates IRC obser vations relatively close to the SAA region say 5 minutes after the passage Chapter 5 Data Reduction and Products This section describes the data handling policy current scope of the data reduction support and data products particularly for phase 3 observations Please note that the data reduction software is under development and only a preliminary plan is explained here Details of the data handling and data reduction guide are prepared as Instrument Data User Manuals The data reduction steps for phase 3 IRC observations are performed in a similar manner to those for phase 2 However the very same software that is used for phase 2 data may not be applied The software specific to phase 3 observations is currently being developed ol 52 AKARI Observer s Manual 5 1 Basic Policy The reduction of pointing observation data is the observer s responsibility The AKARI team will provide the necessary information to handle the data e g calibration data and software to correct instrument related chara
8. will continue its programmed exposure sequences but of course those data acquired during the maneuver are useless and will not be provided to the users Current AOTs assume that one pointed observation could last longer than 10 minutes and add extra exposure cycles at the end 38 AKARI Observer s Manual 44 The IRC AOTS The Astronomical Observation Templates AOTS of the IRC are summarized in Table 4 4 5 Five AOTS are defined for the instrument Note that the actual AOT sequence has been modified from phase 2 and thus the designation of the AOT is changed from that used in phase 2 AOTs are now called Z rather than 0 where the same number indicates the corresponding AOT in phase 2 The largest modification in the observation sequence consists in 5 dark frames before and after the actual observation to obtain information on the dark current for each observation There are also more options parameter combinations available for each AOT Table 4 4 5 IRC AOTS and user parameters Purpose F of filters Dithering per ch Deep imaging 3 choices Imaging with 2 filters ch 3 pos e 2 choices N Imaging with 3 filters ch 2 pos filter N A fixed N Spectroscopy No 2 choices Ns Np Nh Nc The procedures for the AOT operations for IRCZO Z2 Z3 and Z4 are shown in Figure 4 4 6 As explained in the previous section 4 3 1 an AOT consists of a combination of exposure cycles indicated as exposure cycle Filter Wheel rotations
9. 300 1000 Mo yr with a median redshift of 2 4 Chapman et al 2003 The star formation rate at z 1 requires significant evolution in the IR galaxy population from the current epoch Deep observations with the Spitzer Space Telescope have confirmed this strong evolution in the galaxy population out to ISO redshifts and furthermore provided insight into the higher redshift Universe in the so called redshift desert z 1 3 Papovich et al 2004 To connect the local and intermediate redshift IRAS ISO Universe to the higher and high z Universe observed by Spitzer and SCUBA comprehensive multiwavelength imaging is required throughout the extragalactic populations Observations have been during Phase I and Phase II of the AKARI mission with the IRC MIR S amp MIR L cameras which have observed the full mid infrared wavelength range in 6 bands from 7 24 wm to much higher sensitivities than obtained in the previous ISO surveys Elbaz et al 2002 in order to constrain the dusty mid infrared spectra of these sources Our targets are the same sources but at shorter wavelengths Just as the mid infrared observations can constrain the star formation history of the Universe the shorter near infared wavelength bands can constrain the mass assembly history through the observation of the older stellar populations of these sources It is known the stellar mass correlates well with the central black hole mass in massive galaxies Magorrian et al 1998 and by combining t
10. Mode AKARI provides four reasonable methods for spectroscopy of distant galaxies e Slitless spectroscopy in the main 10x10 arcmin field of view using NP prism e Slitless spectroscopy in the main 10x10 arcmin field of view using NG grism e Slit spectroscopy using the NP prism in the 1x1 arcmin point source aperture e Slit spectroscopy using the NG Grism in the 1x1 arcmin point source aperture Observations using the slits Nh Ns are not appropriate for point source observations due to insufficient pointing accuracy and should be avoided The slitless spectroscopy with AKARI using the NP prism creates low resolution spectra over the entire field of view of the imaging plane However to obtain the sensitivity using NP to detect the contiuum of most distant sources we would have to integrate so far down that we would run into source confusion problems with multiple overlapping source spectra The confusion problem with the NG grism in slitless mode is compounded by an even bigger wavelength dispersion more overlapping sources For the detection of lines using the 1x1 arcmin point source aperture the resolution of the NP element is too low Therefore we find that indeed slit spectroscopy using the high resolution grism on the IRC is the most efficient method to observe our distant galaxies Current estimates of the detection limit for lines in Phase 3 compared to the earlier phases of the mission assumes a degradation of at least a factor of two
11. S camera which uses only two lenses A filter wheel is placed at the iris of each camera Three filters two dispersion elements and a blind mask are prepared for each camera The blind position is used for dark measurements during the flight operation 28 AKARI Observer s Manual 4 1 3 Filters and Dispersion Elements Table 4 1 2 shows the filters and the dispersion elements of the NIR channel of the IRC The NIR camera covers three independent wavelength bands that very roughly correspond to the well known K L and M bands The two dispersion elements of the NIR camera provide different spectral resolutions over a similar wavelength range Table 4 1 2 IRC Filters and Dispersion Elements OTOTOTO 6 Channel Name Aret Wavelength Dispersion um um umm pix N2 2 4 N3 3 2 NIR 0 06 at 3 5 um 0 0097 4 5 Reference wavelength Defined as where the responsivity for a given energy is larger than 1 e of the peak Isophotal wavelength of the filter band for Vega Effective bandwidth Dispersion power of prism depends on wavelength The actual resolution can be estimated assuming point spread function see Table 4 2 4 SS KP KP RE 6 7 8 Version 1 1 June 12 2008 29 4 1 4 Field of View FoV Figure 4 1 1 shows the location of the FoV of the three IRC cameras on the Focal Plane projected onto the sky See also Figure 2 4 7 As noted earlier the NIR and MIR S cameras observe the same FoV on the sk
12. change and Micro Scan inserted between them The operation sequence of the exposure cycle is designed by the IRC team to optimize the performance of the instrument and observation efficiency The design of an exposure cycle is illustrated in Figure 4 3 5 The unit time length for a detector driving is 2 3376 seconds which corresponds to the time for the NIR detector to access all pixels in the array Time durations in the exposure cycle are always a multiple of this unit time One exposure cycle takes 28x unit time 65 4528 s The NIR detector carries out one short 2x unit time 4 6752 sec and one long exposure 19x unit time 44 4144 sec in a cycle The short exposure is useful for bright stars that may saturate the detector However the photometric accuracy of the short exposure is worse than the long exposure Fowler 4 sampling is taken for the longer integrations to reduce the readout noise by a factor of two Two images from the NIR channelare produced in one exposure cycle They are stored in the frame memory buffer then divided into telemetry packets and down linked to the ground The on ground data reformatting software will reconstruct the frame memory buffer and eventually a set of images which are then passed to the observers Output signal 6545286 Ae gt Reset I4 6752s 44 4144s lt gt bs gt Data trahsfer Fowler 4 Time Figure 4 3 5 Illustration of the operation of one exposure c
13. during a pointing opportunity The exposure cycle is simply repeated until the end of the pointed observation No filter change nor dithering operation is inserted It is expected that observations with other filter s and data redundancy by dithering are taken on additional pointing opportunities It is strongly recommended to observe the same sky position with at least three independent pointings with the same filter setting The necessary number of pointings is then multiplied by the number of filters Therefore IRCZO is only applicable in very high visibility regions at high ecliptic latitudes It is recommended for observers to use this mode only in areas of the sky that can be observed more than 6 times three dithers two filters Due to operational constraints it is very difficult to ensure such high visibility for Open Time and thus use of this mode has to be planned with great care If the multiple observations are requested under the same target ID small shifts of the pointing position among independent pointing observations dithering operation among pointing observations are automatically arranged in the scheduling software Observers who wish to set the observation positions by themselves should specify the target position in each pointing opportunity and should not use multiple pointing assignments Parameters Only the filter to be used can be specified as defined in Table 4 4 7 The FoV reference position is fixed at the center of the N
14. filter set and the second is the position of the slit The NIR camera has 3 slits A common slit with the IRC MIR S camera for spectroscopy of diffuse sources using the NP element an entrance aperture for point source spectroscopy and another slit for high resolution spectroscopy with the NG element We wish to carry out both high resolution spectroscopy with the NG element at the and lower resolution spectroscopy with the NP element so we require an entry in the target list for both sets of observations for each target making a total number of four lines in our target list In addition since no dithering is carried out during this AOT we must observe each sky area at least twice for data redundancy Therefore we are looking at a minimum of 2 pointings per target per observation mode For our fainter target the high visibility SMP83 we will decide to double the number of pointings to ensure high signal to noise detection of our lines The complete target list is shown in Table 1 3 5 Table 1 3 5 Target List for submission 1 NGC7027 J2000 21 07 01 7 42 14 11 0 IRCZ4 b Nh 2 A NGC7027 high resolution 2 NGC7027 J2000 21 07 01 7 42 14 11 0 IRCZ4 a Ns 2 C NG C7027 lower resolution 3 SMP83 J2000 05 36 21 0 67 18 14 0 IRCZ4 b Nh 4 B 5MP83 high resolution 4 SMP83 J2000 05 36 21 0 67 18 14 0 IRCZ4
15. for the required sensitivity for the detection of the target lines are between 8 10 pointings per target We conservatively select 10 pointings per source since the visibility constraints are not harsh Not that the number of hot pixels in the IRC NIR camera have also increased dramatically in Phase 3 of the mission and a large number of pointings is important to ensure adequate dithering of our observations Now the appropriate AOT has been selected we can go ahead and prepare the target list for our observations An AKARI target list contains one line per target per AOT per field of view Since we are only observing our target fields with the IRC NIR NG grism we will have four lines in our target list one per target galaxy The target list is shown in Table 1 2 2 The target list consists of a unique I D in ascending but not necessarily contiguous order followed by some identifier for the target name which should if possible be a resolvable by systems such as SIMBAD NED The next 3 fields are reserved for the coordinate system and target coordinates we enter these in J2000 equatorial coordinates in the HH MM SS S format although degrees are also acceptable Coordinates entered in ecliptic format should b in decimal degrees Next we need the AOT which will be IRCZ4 Following the AOT are the specific parameters for each given AOT For the IRC we have to specify 2 parameters the filter combination prism or grism and the aperture
16. in the same manner as described in the earlier sections The results of the Visibility Tool for our fields are shown in Figure 1 4 12 the columns have already been explained in the first example in the cookbook section The constraint on visibility can again be clearly seen in the input target fields The Marano field is at a moderate ecliptic latitude of 35 degrees above the ecliptic while the COSMOS amp UDS fields is only 9 amp 17 degrees below the ecliptic plane respectively and is thus heavily constrained only a total of 8 amp 7 pointings in Phase 3 Combined with the poor visibility we also find the Moon in the COSMOS field and it is thus probably unlikely that we will be able to carry out all our desired pointings Therefore we shall drop the COSMOS and UDS fields and concentrate on the remaining three fields The output from the visibility tool should be saved as an ASCII file as it will need to be uploaded as part of the final submission process for our proposal or Phase 3 Open Time Visibility Tool Batch Mode AKARI Visibility Batch Query Start Fri May 16 11 59 12 2008 CEST 9 8130 66 8079 29 38 67 2 J 2000 03 11 00 0 54 45 00 0 ID 1 IRC ISO 31 4683 17 5371 1 6 7 2 J 2000 02 21 20 0 04 30 00 0 ID 2 IRC UDS 151 4168 9 3643 6 2 8 2 J 2000 10 00 28 60 02 12 21 01 ID 3 IRC COSMOS 148 3631 57 2859 9 15 24 2 J 2000 12 36 49 9 62 12 58 0 ID 4 IRC HDF 346 8286 43 2496 8
17. layers of Vapour Cooled Shield VCS in which Helium vapour evaporated from the tank was running through The inner VSC is also cooled by the mechanical coolers The SIA was mainly cooled by the Helium vapour down to about 6 K The FIS body and two detectors are directly connected to the Helium tank via thermal straps and were operated at 2 0 2 2 K After the liquid Helium boiled off the SIA is kept around 40K and near infrared observations are being carried out Figure 2 2 3 The AKARI Cryogenic system in the clean room for maintenance Left The Cryostat Right Close up of the Two Stage Stirling cooler Photo July 2005 Version 1 1 June 12 2008 9 2 3 Telescope 2 3 1 Specification The telescope is a Rithcy Chr tien system with an effective aperture of 68 5 cm and a focal ratio of 6 1 Figure 2 3 4 The mirrors are made of SiC porous CVD coated material This rigid material allowed to reduce the weight of the mirrors significantly The primary mirror with a physical diameter of 71 cm weighs only 11 kg The total weight of the telescope system is 42 kg The focus may be adjusted in orbit during the PV phase by moving the position of the secondary mirror The parameters for the telescope are summarized in Table 2 3 1 The primary mirror was replaced in 2004 as a part of a refurbishment of the telescope system The effective aperture has been increased slightly previously 67 cm The telescope has been tested in the cryogenic vibr
18. outputs of the Visibility and Duplication Tools Version 1 1 June 12 2008 69 Query target list S 0 A 2 B 4 C 6 D 0 total 12 search radius 5 000 arcmin 4 targets in your list are duplicated with the blocked target list ID R A Dec AOT Target name Result 1 316 757 42 236 IRCZ4 b Nh NGC7027 A Duplication 2 JAE A ID R A Dec AOT Target name d status AA 4081016 316 757 42 236 IRCO4 b Ns NGC7027 CERN1 B 0 0 Observed 1740550 316 757 42 236 IRCZ4 b Np NGC 7027 AGBGA B 0 0 Scheduled AAAAAARAAAAAAAAARAAARARARAAAAAAAAAAAAAARAAAAAAAAAAAARARAAARAAARARARANAAAAAARARAAAAAAARAAAAAAAADBAAARARAAAAAAA 2 316 757 42 236 IRCZ4 a Ns NGC7027 C Duplication 2 AAAAAARAAAAAAAAARAAARARAAAAAAARAAAAAAAAARAAAAAAAAARAARARAAAAAAARARARAAAAAAAADRARAAAAAAARAAAAAAAAAAAARARAAAAAAA ID R A Dec AOT Target name d status AA 4081016 316 757 42 236 IRCO4 b Ns NGC7027 CERN1 B 0 0 Observed 1740550 316 757 42 236 IRCZ4 b Np NGC 7027 AGBGA B 0 0 Scheduled AAAAAARAAAARRAAMNARARAAARARARARARARNARAAAARARAAAAARARARAARAANARAAAAAARAARARAAARARARAARAAAAAARAAAAARAAARAAAAARARA A 3 84 088 67 304 IRCZ4 b Nh SMP83 B Duplication 1 AAAAAARAAAARAAANARARAAARARARARARARNARAAAARARAARARARAAARARAARAAAMARARAAAAARAAARARAANARAAAAAAAAARARARARARARAARARA A ID R A Dec AOT Target name d status A o EE EE EE EE N 1740328 84 087 67 302 IRCZ4 b Np LMC SMP083 AGBGA A 0 1 Scheduled AAAAAARAAAARAAAARARBAAAAARARARARARNARAAAARARA
19. the detector just like the imaging mode The line flux can be roughly converted to the continuum equivalent flux density per pixel Fe as F pixel Fi x 10 PSF dv Jy Where dv is estimated from the instrument element resolution i e dA 0 06 amp 0 0097 for NP and NG respectively in um pixel at 3 5um For NGC 7027 most lines are brighter than 10715 W m giving a corresponding continuum flux of 6 7 mJy amp 42 mJy for NP and NG respectively The saturation level of the N3 band is 110 mJy Note that this image does not have to be a particularly high quality image and even if some portion of it is saturated it may still be possible to estimate the wavelength scale Table 1 3 4 SMP83 line strengths Wavelength microns Line Flux 10 W m 2 8 H2 3 0 2 626 Br GB 46 3 74 Pfy 11 0 4 05 Bra 92 4 654 PfB 11 0 Concentrating on just the brighter lines in both nebulae we can see the IRC is sensitive enough to detect these lines in SMP83 in a single pointing Although we still require at least 2 pointings for dithering see below 66 AKARI Observer s Manual A 3 4 Preparation of Target List We intend to carry out high resolution slit spectroscopy with the IRC grism NG in the near infrared as our first priority Following this as our second priority we will observe the same dust spectrum at a lower resolution using the IRC prism NP The spectroscopic IRC AOT for Phase 3 is IRCZ4 This AOT has 2 parameters the first is the
20. to be carried out be using different pointings The observers themselves need do nothing since this operation will be carried out by the mission controllers We then have to prioritize our targets AKARI Open Time Observations are divided into 3 priorities A B C Our A amp B targets barring any unforeseen events should be observed while the priority C targets should be considered as back ups In our target list the number of priority A B C targets should be around the same The objective of the IRC observations is to detect the near infrared emission from massive star forming galaxies to z 1 Although multi band detections are preferred the priority is a detection in at least one band Therefore for our observations we prioritize by IRC filter although we could just as easily prioritize by the observation field instead for example We select the IRC N3 and N4 bands as priority A B respectively The N2 band is prioritized as C since in fact it is possible to make observations from the ground at this wavelength 24m Again as in the previous example we choose not to link our observations together as symbi otic since for our targets we could still get useful information even with a partial observation so we do not want the extra constraint of symbiotic observation therefore we will leave the field blank not forgetting the comma field separator Finally any notes are appended on the end of each target list line Our final tar
21. to the imaging area has a 5 arcsec width and was mainly used for simultaneous observations of diffuse light with the MIR S camera This slit position is labeled as Ns for IRCZ4 AOT observation parameter Both the NP low resolution prism and NG high resolution grism will be used with this slit The middle 1 x 1 square part referred to as Np is for spectroscopy of point sources The aperture is large compared to the absolute pointing accuracy of the satellite designed to be better than 30 arcsec to ensure that the target can be accurately guided into the area Note that for observations of faint sources confusion due to galaxies may be a serious problem The NG grism is assumed to be used with this aperture The rightmost outer 30 AKARI Observer s Manual part Nh has a 3 arcsec width and is used for the highest resolution spectroscopy of diffuse radiation with the NG grism 4 1 6 Detectors The detectors of the IRC are provided by Raytheon IRCoE The NIR camera has an InSb detector array of 512 x 412 pixels SBRC 189 in which 391 x 412 pixels are used for imaging and the other 121 x 412 pixels are for slit spectroscopy It is known that the detector performance sensitivity changes with temperature All detector arrays are equipped with thermometers to monitor the module temperature during their oper ation In phase 3 it is noticed that the number of hot pixels in the NIR detector is increased drastically from p
22. 0 shows the iris_sky tool with the outmost slit of the IRC NIR camera positioned over the target NGC7027 In this figure the entrance aperture for point sources and the common inner slit for diffuse sources can also be seen Version 1 1 June 12 2008 File TargetList Image Plot Value 4 7282E 02 Position 21 07 05 789 42 20312 16 J2000 sexagesimal latitude 42 14 10 18 sl ind New Edit Load Savel Deletel Renumber 10 67 Figure 1 3 10 Using the iris_sky tool to overlay the IRC NIR high resolution spectroscopy slit Nh over the Planetary Nebula NGC7027 68 AKARI Observer s Manual Next we have to choose the slit parameter For the high resolution spectroscopy this param eter is Nh the target position is placed at the high resolution slit of the NIR camera For the lower resolution spectroscopy the parameter is Ns We set the number of pointings as 2 for the brighter source and 4 for our fainter source For this example we prioritize our targets by the high and low resolution spectroscopy giving thigh resolution observations with NG a priority A amp Band the lower resolution spectroscopy with NP priority C respectively Again as in the previous example we choose not to link our observations together as symbiotic since we can still get decent scientific results with either the high or low resolution spectroscopy A 3 5 Target List Validation The Target List synt
23. 10 A redshift 1 488 3 SMMJ123549 621536 J2000 12 35 49 44 62 15 36 8 IRCZ4 b Np 10 B redshift 2 2032 4 SMMJ221733 001352 J2000 22 17 33 91 00 13 52 1 IRC10 b Np 10 C redshift 2 5510 AOT name does not exist options are IRCZ0 IRCZ2 IRCZ3 IRCZ4 Pointings Total 20 S 0 A 10 B 10 C 0 D 0 Format error 1 Figure 1 2 5 Output from the Target List Validation Tool Any Errors are marked in red and the number of errors are listed at the bottom of the output in the Pointings summary In this case an AOT has been input incorrectly Version 1 1 June 12 2008 61 A 2 6 Duplication Check Duplicate observations are decided on a basis of position instrument AOT and the number of pointings Figure 1 2 6 shows the input screen for the Duplication Check Tool This tool returns all IRC observations within a radius of 5 arcmins from the requested targets which are either executed in the cold phase Phase 1 and 2 or are in the blocked target list for Phase 3 The observations executed in the cold phase are in the public domain at the time of Phase 3 Open Time A strict duplication occurs when AOT and parameters of a requested target are identical with those of a Phase 3 observation The other cases returned by the tool may have to be discussed in the proposal scientific justification The output from the duplication tool is shown in Figure 1 2 7 and we can see that all our targets pass the D
24. 54 750 IRCEO b M IRC 130 A OR 2 47 750 254 750 TRCEO e N IRC 130 B OR 3 47 750 54 750 TRCEO aN IRC 130 C OR 4 189 208 62 216 IRCEO D N IRC HDP A Duplicatian 6 SELES SLES LESS LESSEE EL EL EE EE EERE EEE EEE EEE DER DER DE EERE Ib R A Dec MOT Target name 4 status carac ME EE EE EE EE SEBS SEES BEES EEE BEBE GG kk A A a 1320028 189 208 62 216 IRCOS c N COGDS N 11 4 PUHYU A 0 0 Observed 1320029 189 208 62 216 IRCOS c3N GOODS M 11 4 PUHYU A 0 0 Observed 1320030 189 208 62 216 IRCOS c3N COGDS N 11 4 PUHYU A 0 0 Observed 2 1320031 189 208 62 216 IRCOS c3N GOGDS N 11 4 PUHYU A 0 0 Observed 2 1320032 189 208 62 216 IRCOS c3N C00M3 N 11 4 PUHYU A 0 0 Observed 1320033 189 208 62 216 IRCOS c3N COODS M 11 4 PUHYU B 0 0 Observed 5 189 208 62 216 IRCEO c3N IRC HDP B Duplication 18 PERSE EE SELLS LLL DE EE SPEED DEE DS EE SESSLER DS EED DEE DE DE DS DE DE EED DEE DT EDE ED EE DE EED DEE DE EED DEE DE EE PD DEE DE EE PD EES Ib RA Dec MOT Target name di status AAA 1320028 189 208 62 216 TROOS N COGDS N 11 PUHYU A 0 0 Observed 1320029 169 208 62 216 IRCOS ciN COODS N 11 4 PUHYU A 0 0 Observed 1320030 189 208 62 216 IRC05 c N COGDS N 11 4 PUHYU A 0 0 Observed 1320031 189 208 62 216 TRCOS eiN GOODS W 11 4 PUHYU A 0 0 Observed 1320032 189 208 62 216 IRCOS c3N COGDS N 11 4 PUHYU A 0 0 Observed 1320033 189 208 62 216 IRCOS c3N GOODS N 11 4 PUHYU B 0 0 Observed BERE EERDER SS LESS ELLE LES
25. 733 001352 J 2000 22 17 33 91 00 13 52 1 Version 1 1 June 12 2008 55 A 2 2 Selection of Targets and Target Visibility A Visibility Tool is provided that gives an approximate estimation of the open time visibility of the target field during the Phase 3 of the AKARI mission assuming an observation period of October 2008 to October 2009 The following constraints are imposed on the target visibility 1 The instrument is of 10 arcmin width and at the boresight 2 The maximum number of observations in a day is about 20 since 30 of the total number of pointings with AKARI are reserved for Open Time which translates roughly into 6 orbits every day or almost a degree interval on the ecliptic longitude 3 The same constraints on the SAA Moon and the number of stars in STT as in the first call will be applied 4 The offset angle to the nominal scan path along the great circle constraint will be relaxed from 0 6 degree but will still be smaller than the maximum 1 degree to ensure a safety margin for scheduling 5 The maximum number of pointed observations at any single pointing has a ceiling set at 50 In addition to the above any orbits not scheduled for the Mission Programs are available for scheduling for open time However visibility for specific targets is quite heavily constrained and an extremely strong function of ecliptic latitude Targets in the ecliptic pole regions are observable ona large number of orbits while targe
26. 8 16 2 J 2000 00 38 30 0 44 00 00 0 ID 5 IRC ELAIS AKARI Visibility Batch Query End Fri May 16 11 59 13 2008 CEST Figure 1 4 12 Results from the Visibility Tool in batch mode The result shows the total number of allocations possible during Phase 3 of the AKARI mission Each target is listed by position in Ecliptic coordinates visibility in Phase 3b1 2008 Oct 15 2009 Apr 11 179d Phase 3b2 2009 Apr 12 2009 Oct 14 186d and the total visibility in Phase 3 2008 Oct 15 2009 Oct 14 365d The original user input is shown on the right A 4 3 The Choice of Observation Mode The objective of the IRC observations is to detect the near infrared emission from massive star forming galaxies such as dusty ULIRGs There are 3 observation AOTs available for near infrared imaging T2 AKARI Observer s Manual 1 AOT IRCZO Formerly referred to as IRCOO or IRCO5 this AOT carries out the deepest imaging in a single band only 2 AOT IRCZ2 Formerly referred to as IRC02 this AOT carries out intermediate depth imaging in two bands 3 AOT IRCZ3 Formerly referred to as IRC03 this AOT carries out imaging in all three IRC bands N2 N3 N4 The typical flux densities for the colder ULIRGs in the near infrared are around 10 uJy see Figure 1 4 13 For our purpose we require deep images of our fields therefore we will select the IRCZO AOT The current sensitivity estimates for this AOT are 18uJy in all three IRC
27. AKARI Observer s Manual for the Post Helium Phase 3 Mission Version 1 1 for Open Time Observation Planning AKARI User Support Team in Institute of Space and Astronautical Science JAXA contact iris_help ir isas jaxa jp European Space Astronomy Centre ESA contact http akari esac esa int esupport June 12 2008 Revision Record 2008 May 12 Version 1 0 released adapted from ASTRO F Observer s Manual Version 3 2 2008 June 12 Version 1 1 released Cookbook section added in Appendix Contents 1 Introduction 1 1 1 Purpose of this document e 1 1 2 Relevant Informatio ss sos Sas e a A ee A we 3 2 Mission Overview 5 2 1 The AKARI Mission 5 2 9 Satellite ss eos By elas a o a aaa ae 6 2 2 1 The Bus Module ss 2 26444 0806 2404804 a Be eee 6 2 2 2 Attitude Determination and Control System 0 7 22 3 CLYORCNICS k as paniei g ei cece Se a A Hee eR ed ae Be 8 2 3 TeleSGope sec ea gw kd ee we ae eg a ee ee a EE Ep Rd 9 2 3 1 Specification esa eie eee EE ee aw we ROER Ee aD a Ae Ge 9 2 3 2 Capability and Performance in Phase3 0004 10 2 4 Focal Plane Instruments 11 24 1 Specification Overviews esa a a ed ee 11 2 4 2 Focal Plane Layout eee ee eee 13 2 4 3 The Focal Plane Star Sensor FSTS 14 2 5 The AKARI Observation Programms in Phase 3 15 2 6 References x Voq iia dra a o a 16 3 Satellite Operati
28. AKARI spacecraft scales are in mm The Bus Module The bus module takes care of the power supply house keeping spacecraft attitude control data acquisition and the telecommunication link to the ground station AKARI uses the S band mainly for command and house keeping telemetry data and the X band mainly for scientific data for telecommunication Due to its near Earth orbit communication between the satellite and the ground stations is limited Therefore AKARI has a two Gigabyte data recorder Version 1 1 June 12 2008 7 2 2 2 Attitude Determination and Control System The attitude of the AKARI satellite is determined and controlled by on board sensors and a computer unit Figure 2 2 2 shows the block diagram of the attitude and orbit control system AOCS The framework of the system is as follows The IRU Gyro measures the motion of the satellite The TFSS Two dimensional Fine Sun Sensor were meant to monitor the position of the Sun in two dimensions perpendicular to the Sun satellite direction and to correct any long term drift of the IRU signal A pair of Star Sensors STT mounted on the wall of the cryostat are used to observe the attitude along the third axis and the alignment change between the bus module where IRU and TFSS are located and the cryostat in which the telescope is installed Other instruments provide additional information for attitude determination A dedicated computer AOCU determines the satellite att
29. ARARARAAARARAARAAAARARAARAAAAAAARARAARAAAAAARAAAAAAAAAAAAAAARARA A 4 84 088 67 304 IRCZ4 a Ns SMP83 C Duplication 1 JAE TE EIE RE GESE GE EG GE ER GE SEER TE EN GE GEE GE EG GE ER GE ESEG GE GEE GE EER ID R A Dec AOT Target name d status ff Sor cr ase OE NE EO NE EE Ee N irc roots 1740328 84 087 67 302 IRCZ4 b Np LMC SMP083 AGBGA A 0 1 Scheduled JAE EEE EEE Command executed on 2008 05 16_19 48 05 JST Figure 1 3 11 Results from the Duplication Checker Tool We see that our targets are in conflict with guaranteed time on AKARI and a previous OT observation in Phase 2 Duplication can be made on position instrument AOT and the number of pointings 70 AKARI Observer s Manual A 4 Example 3 Near infrared imaging of extragalactic fields with the IRC In this worked example we consider a program to image several deep extragalactic fields with the AKARI IRC NIR instrument We will simulate the preparation of the proposal from scientific background to proposal submission A 4 1 Scientific Background Studies with the Infrared Space Observatory ISO of the Hubble Deep Fields have revealed star formation rates at least comparable to or higher than those of optical UV studies Mann et al 2002 At submillimetre wavelengths surveys with SCUBA on the JCMT have revealed a large gt 3000 deg at 850 gt 2 mJy strongly evolving population of sources with bolometric luminosities gt 10 L and star formation rates of
30. IR camera N Table 4 4 7 Filter parameter of IRCZO N3 N3 M3 Version 1 1 June 12 2008 41 4 4 3 Expected Performance Detection Limits The expected 5c detection limits of the IRCZO observing mode are given in Table 4 4 8 assuming 9 exposure cycles for one filter in a pointing opportunity Table 4 4 8 Detection limits 5 a for AOT IRCZO Point source Diffuse source Hy MJy sr N2 18 0 036 N3 18 0 035 N4 18 0 035 Saturation Limits The saturation limits of the IRCZO mode are given in Table 4 4 6 42 AKARI Observer s Manual 4 4 4 IRCZ2 Imaging and Spectroscopy with Two Filters or Filter and Prism Recommended Usage IRCZ2 mode is prepared for general purpose imaging or spectroscopic observations This mode can be used at any sky position even in low visibility regions Description A sky position is observed with two filters each of which consist of three images with small position shifts by dither i e this AOT can provide a self standing data set in just a single pointing The net exposure time per filter is about 1 3 of IRCZO The IRCZ2 provides a new imaging N3 and prism NP mode in addition to the original IRC02 mode with two filters N3 and N4 The spectroscopic mode provides an imaging and slit less spectroscopic mode with dithering operation which is different from IRCZ4 With the large number of hot pixels dithering operation in one pointing could provide useful redundant information On the o
31. R and MIR S cameras of the IRC share the same FoV so as to observe the same sky position Only the MIR L channel observes a different sky position The scan path is approximately parallel to the Ecliptic meridian line The scan direction depends on the launch configuration namely the launch time morning or evening The actual launch has been in the morning The FoV is thus moving downward i e stars go through the detector from bottom to top on the figure Note that the real position and the shape of each Focal Plane Instrument on the sky will be slightly different from those shown in Figure 2 4 7 due to optical aberration See Section 4 1 4 IRC for details gt 2 Telescope i 82 p ea po 2 Axis y 3 in y 2 oN E a 2 a z A A ES 44 4deg ai N 3 z E 12 4 L n 1 ff 444deg y A N D Su my NA N l FSTS L Figure 2 4 7 Focal Plane layout projected onto the sky The distortion due to the telescope and instrumental optics have to be taken into account for the data reduction See the Instrument Data User Manuals for details 14 AKARI Observer s Manual 2 4 3 The Focal Plane Star Sensor FSTS A pair of star sensors are installed in the Focal Plane The FSTS L consists of four Ge detector elements while the FSTS S has three They observe stars with their intrinsic wavelength band profile close to the J band 1 25 um The readout is a TIA TransImpedance Amplifier circuit w
32. SEE EE EED ELLE EEE EE ER EE EE EE EE DE EERE EE EE ER DE DEE DS EDE ER DE EED DER DS EE DE eee ees 6 189 208 62 216 TRCEO aN IRC HDP C Duplication 48 dad 1D R A Dec AQT Target name di status B89 AAA AAA AAA AAA AAA cara 1320028 189 208 62 216 TRCOS e iN COGDS N 11 4 PUHYU A 0 0 Observed 1320029 189 208 62 216 IRCOS c3N COGDS N 11 4 PUHYU A 0 0 Observed 1320030 189 208 62 216 IRCOS c3N GOODS W 11 4 PUHYU A 0 0 Observed 1320031 189 208 62 216 IRCOS c3N GOODS W 11 PUHYU A 0 0 Observed 1320032 189 208 62 216 IRC05 c N GOQDS N 11 PUHYU A 0 0 Observed 1320033 189 208 62 216 IRCOS ciN GOODS N 11 4 PUHYU B 0 0 Observed SESS ESL SEED SEED SEED SPEED DEE DS SE SES SESS EED DEE DS EED DEE AAA EE EE DE EE SPEED DE EE DE DEE See ee eS 7 9 625 s44 000 TRCED PIN IRC ELAIS A OR 8 9 625 44 000 TRCED eN IRC ELAIS B OR 9 9 625 lt 44 000 TRCED AN IRC ELAIS C OR Command executed on AR IS DIST IST Figure 1 4 14 Results from the Duplication Checker Tool We see that 3 of our observations are in conflict with the guaranteed time on AKARI 76 AKARI Observer s Manual A 4 7 Submission of Proposal After the duplication check we can finally submit our proposal via the web interface The proposal submission has several stages and we will need to upload various output files saved from the tools we used earlier Each proposal has a 5 character abbreviation which will be used to identify each proposal The next ste
33. SO FIRBACK IRC HDF 32000 12 36 49 9 62 12 58 0 IRCZO b N 3 A HDF N IRC HDF 32000 12 36 49 9 62 12 58 0 IRCZ0 c N 3 B HDE N IRC HDF J2000 12 36 49 9 62 12 58 0 IRCZ0 a N 3 C HDF N IRC ELAIS J2000 00 38 30 0 44 00 00 0 IRCZ0 b N 3 A ELAIS S IRC ELAIS J2000 00 38 30 0 44 00 00 0 IRCZO eN 3 B ELAIS S IRC ELAIS J2000 00 38 30 0 44 00 00 0 IRCZO a N 3 C ELAIS S O 0 IDO order followed by some identifier for the target name which should if possible be a resolvable by systems such as SIMBAD NED The next 3 fields are reserved for the coordinate system and target coordinates Following the AOT are the specific parameters for each given AOT For the IRC imaging we have to specify 2 parameters the filter combination and the camera with which we want to observe For the IRCZO AOT the filter can be chosen from parameters a b or c N2 N3 amp N4 respectively We require one target list line for each The second parameter can only be N corresponding to the IRC NIR camera In the following field we input the number of pointings for each AOT for our case this has to be at least 3 for each IRCZ4 AOT The reason for this is that this particular AOT like the spectroscopic IRCZ4 AOT is not dithered and the dithering has
34. Surveyor FIS for AKARI Kawada M et al 2007 PASJ 59 S389 IRC The Infrared Camera IRC for AKARI Design and Imaging Performance Onaka T et al 2007 PASJ 59 S401 IRC spectroscopy Near Infrared and Mid Infrared Spectroscopy with the Infrared Camera IRC for AKARI Ohyama Y et al 2007 PASJ 49 411 Chapter 3 Satellite Operations 3 1 Orbit and Observing Attitude The orbit of AKARI is a Sun synchronous polar orbit along the twilight zone with an altitude of 700 km corresponding to an orbital period of 100 min After the liquid Helium boil off the orbit was readjusted to a nearly ideal Sun synchronous polar orbit In principle the spacecraft always points in the direction perpendicular to the Sun Earth line keeping the Sun shield towards the Sun and rotates once per orbit to look out in the opposite direction to the Earth The spacecraft attitude in the cross scan direction has a flexibility of 1 degree about the canonical scan path 89 91 deg from the Sun inti Pointing Stabilize Return to 10 min 5 min A Survey 7 5 min A le A Attitude Change lol Maneuvour 7 5 min M Continuous Survey Figure 3 1 1 The in orbit attitude of AKARI left and the pointed observation maneuver right In the survey mode the satellite is operated such that the telescope scans the sky with a constant speed 3 6 arcmin sec usually along the great circle at a solar elongation of 90 de
35. and there is still a great deal of uncertainty surrounding the actual values For the proposed NIR spectroscopy with AKARI in the 2 5 5um range by using the IRC grism a line sensitivity of 5x10 Wm for a 10 minute integration is achieved In Figure 1 2 3 we show the predicted line strengths for the Hydrogen recombination lines Paschen a amp as a function of redshift assuming an ultra luminous infrared galaxy similar to our targets with an infrared luminosity of 5x 10 7Lo In general we may require between 8 to 10 pointings to detect our sources at z gt 1 100 Hydrogen Recombination Line strength for 5x10 Lo ULIRG Line Strength 1018 W m 0 1 l 0 5 1 1 5 2 2 5 3 Redshift Figure 1 2 3 Predicted Hydrogen recombination line fluxes for a 5x10 2L Ultraluminous In frared Galaxy 58 AKARI Observer s Manual A 2 4 Preparation of Target List The objective of our IRC observations is to detect the Hydrogen recombination lines in dusty distant galaxies as explained in the previous section the optimum instrument configuration for this objective is to use the IRC in NG grism mode with our target located in the point source aperture Np Thus we require the following AOT parameters e AOT IRCZ4 note the insertion of the Z in the original AOT name for Phase 3 e Parameter 1 b corresponding to the grism NG e Parameter 2 Np The target is placed in the point source aperture of the NIR channel Our estimates
36. as MglIV etc For our first target NGC7027 all the lines are brighter than 10715 W m Bernard Salas et al 2001 therefore this is well above the IRC detection limits and should be easily observable in a single pointing For our second target SMP83 as a first approximation we can scale the line fluxes of NGC7027 by the distance to the LMC Under this assumption we could expect the H2 line at 2 8 microns to be of the order of 3 0 x 107 W m and the Br alpha line at 4 05 microns to be 92 0 x 107 Wm A non exhaustive list of example brighter line strengths estimated for SMP83 is given in Table 1 3 4 Fainter lines e g He I 4 6 H I 6 15 6 17 transitions are of the order of 10718 W m2 and maybe be more difficult to detect at the IRC line detection limits Note that the saturation level for the NIR detectors is also significantly degraded for AKARI Phase 3 observations For the grism and prism we could expect saturation limits of as low as few x 1071 Wm which may pose problems for our brighter lines In addition there is a degradation in the saturation level of the continuum of around a factor of 5 This is important since the N3 imaging data taken in IRCZ4 is necessary to determine the wavelength origin A rough estimation of the flux level that can be expected can be calculated by assuming an unresolved line with Flux Fi W m62 without continuum where the dispersion elements works like a narrow band filter and we get the image on
37. ased both in numbers of detected sources and areal coverage e g Scott et al 2002 with the flagship being the SCUBA Half Degree Extragalatic Survey SHADES Mortier et al 2005 covering 0 25 square degrees over two fields The lack of any secure evolutionary picture of submm galaxies is partly due to fact that the observational results on submm galaxies are very limited Until recently the only photometric data available for most of submm galaxies was found mainly at NIR and submm wavelengths This lack of photometric data has been alleviated somewhat with mid infrared observations with Spitzer and AKARI although more detailed diagnostics on the observed diversity and the evolutionary phase of these sources could be given by spectroscopic observations of a statistical sample of massive starburst galaxies For example the ratio of Hydrogen recombination lines can be used to es timate the extinction of starburst galaxies which may cause the observed diversity Once the extinction is estimated from spectra the extinction corrected luminosity of the emission lines can be used to derive the SFR independently of the observations of dust emission Note that the SFR derived from submm fluxes depends on assumed dust temperatures which are degenerate Dunne et al 2000 Measurements of the extinction and the SFR from the emission lines independent of the photometric data are a key step to investigate the evolutionary phase of high z massive galaxies Th
38. ation tests and the mirror support system which previously had a problem has been confirmed to be secure Figure 2 3 4 The AKARI telescope system Table 2 3 1 Telescope Specification Effective diameter 68 5 cm primary mirror Focal length 420 cm Focal ratio 6 1 Optical design Ritchey Chr tien type 10 AKARI Observer s Manual 2 3 2 Capability and Performance in Phase 3 Mirror surface accuracy has been measured at cryogenic temperatures to be as low as 9 K Due to thermal stress at the supporting points the wave front error becomes larger at low temperatures and is at its worst at around 50 K The in orbit performance of the AKARI telescope system was measured to be diffraction limited at a wavelength of 7 3 ym at 6K The image quality in phase 3 has been estimated to be by about 10 degraded from that at 6 K after the focus adjustment During the Helium period the stray light scattered off the top of the baffle was noticed particularly during the periods around solstices This stray light is expected to persist in phase 3 and observations of diffuse emission need to be arranged carefully AKARI phase 3 observations provide a unique capability in broad band imaging with a large FoV 10 x 9 3 as well as low resolution spectroscopy in 2 5 um In particular the spectroscopic mode provides slit less spectroscopy for the first time in space missions It enables efficient multi object spectroscopy in one pointing observati
39. ax is validated in an identical manner to the previous example in Section A 2 The target list will also be automatically validated when we upload it during the final proposal submission stage so there is no need for us to save the output of the Validation Check Tool at this stage A 3 6 Duplication Checker Duplicate observations are decided on a basis of position instrument AOT and the number of pointings The Duplication Tool returns all IRC observations within a radius of 5 arcmins from the requested targets Putting our target list into the duplication checker we find that indeed there is a conflict of position for both of our targets see Figure 1 3 11 Although the targets are indeed duplicated with a previous program during Phase 2 and another program planned for Phase 3 the AOTs are slightly different and it my fall to the responsibility of the Telescope Allocation Committee s interpretation of our scientific justification as to whether we can observe our targets The output from the Duplication Check tool should be saved as an ASCII file as it will need to be uploaded as part of the final submission process for our proposal A 3 7 Submission of Proposal After all the tools have been used and the Target List checked we can finally submit our proposal via the web interface in an identical manner as that described for the previous imaging example in SectionA 4 Remember that we will need to upload the previously saved ASCII files from the
40. bands which should be adequate to detect our sources the multiband IRC AOT IRCZ3 has a sensitivity of around 40uJy which will probably be too shallow to detect our sources 103 Er o 100 10 0 1 Flux mJy 0 01 0 001 Infrared Galaxy L 2 5x10 L L 1 Ma a Ma ae eae 0 0001 po EN 1 10 100 108 wavelength um observed frame Figure 1 4 13 Estimated required sensitivities to detect dusty ULIRGs to redshift unity We assume a single pointing with AOT IRCZO A 4 4 Preparation of Target List Once the AOTs have been selected we can go ahead and prepare the target list for our ob servations An AKARI target list contains 1 line per target per AOT per field of view We are observing our target fields with the IRC NIR camera using AOT IRCZO therefore we have 3 lines in our target list per target field one each for the N2 N3 amp N4 bands We have 3 target fields therefore we have a total of 9 lines in our target list The target list is shown in Table 1 4 7 The target list consists of a unique I D in ascending but not necessarily contiguous Version 1 1 June 12 2008 73 Table 1 4 7 Target List for submission IRC ISO J2000 03 11 00 0 54 45 00 0 IRCZO b N 3 A ISO FIRBACK IRC ISO 32000 03 11 00 0 54 45 00 0 IRCZO eN 3 B ISO FIRBACK IRC ISO 32000 03 11 00 0 54 45 00 0 IRCZO a N 3 C I
41. carried out until phase 3 observations will start The start of the phase 3 observation is now planned to be on June 1 2008 for Mission Programmes and October 15 2008 for Open Time programmes Version 1 1 June 12 2008 23 3 4 Sky Visibility As noted earlier the direction of the telescope pointing is always perpendicular to the direction toward the Sun with a flexibility of 1 deg in the cross scan direction Since AKARI is in a polar orbit the visibility defined as the number of scan paths covering a particular sky position is a strong function of ecliptic latitude Targets in the ecliptic pole regions are observable on a number of orbits while targets near the ecliptic plane are visible by AK ARI for only two days 29 orbits in a half year at most In addition visibility is also affected by the SAA South Atlantic Anomaly where a large flux of charged particles disturbs the observation when the satellite pass through the region and the Moon the moonlight can enter the telescope aperture The avoidance angle is 33 deg Observers should understand that opportunities to observe particular objects or fields with AKARI are strictly limited and are a strong function of the ecliptic latitude It is strongly recommended to the observers to check the visibility at each target position A Web interface visibility check tool is provided on the Phase 3 observers pages with which the observers can check the visibility Notes for the Solar S
42. cated For details of the data processing please see the IRC Data User Manual 25 26 AKARI Observer s Manual 4 1 Hardware Specification 4 1 1 Overview The IRC consists of three cameras NIR MIR S and MIR L covering the wavelength ranges of 2 5 5 13 12 26 um respectively In Table 4 1 1 the specifications of each camera are listed See also figure 2 4 5 and 2 4 6 Note that only the NIR is available for phase 3 observations Table 4 1 1 Specifications of the Infrared Camera IRC Chamd NR MIR S MIR L ea Si As CRC 744 Si As CRC 744 512 x 412 256 x 256 256 x 256 9 3 x 10 0 9 1 x 10 0 10 3 x 10 2 Imaging i APE 391 x 412 233 x 256 246 x 256 Pixel Size arcsec 1 46 x 1 46 2 34 x 2 34 2 51 x 2 39 Wavelength um 8 5 4 6 13 4 12 6 26 5 Filters N2 N3 N4 S7 SOW S11 L15 LI8W L24 Dispersion Elements NP NG SG1 SG2 LG2 Cross scan x in scan Masked areas are excluded Each camera is equipped with three filters and two dispersion elements The filter selection is preset in the Astronomical Observation Templates AOTs Section 4 4 and cannot be freely chosen by the observers Version 1 1 June 12 2008 27 4 1 2 Optics All three cameras of the IRC are off axis refractive optical systems Each camera uses 2 5 lenses A Ge beam splitter divides the light between the NIR and MIR S cameras Transmitted light comes into the NIR channel Chromatic aberration does exist in the cameras and is largest in the MIR
43. cteristics Astronomical analysis such as point source extraction should be carried out by commonly available software We welcome any users to participate in the data reduction activity at any level of the work from giving quantitative reports of their data reduction results to proposing new algorithms to the programs 5 1 1 IRC Data Reduction AOT IRCZO Z2 Z3 IRC imaging mode data reduction is straightforward following a similar procedure to ground base observations There are instrument specific corrections such as removing ghost images and spikes by charged particle hits Our support is limited to correction and calibration of each observation We do not plan to support photometry of the calibrated images or mosaicing Currently the system is developed in the IRAF environment Exporting it to IDL is TBD 5 1 2 IRC Data Reduction AOT IRCZ4 Data reduction of this mode is similar to that of the imaging mode for the basic processing of the dark subtraction despiking or bad pixel masking etc In this AOT an image is also taken with the N3 filter Source positions are extracted from this image and applied to the spectroscopy images to clip each target Several relevant technical issues for the spectroscopic observations are listed below e For reliable spectroscopic observations we need accurate and wavelength dependent flat fielding e Wavelength calibration is automatically made by the relationship between imaging posi tion and th
44. d out in early 2008 Note that some of the instrumental performance information was not yet available by the time of the publication of this version of the manual Frequent updates will be given on the Observer s support Web page AKARI Observer s Manual Figure 1 1 1 AKARI ASTRO F waiting for the launch January 2006 Version 1 1 June 12 2008 3 1 2 Relevant Information AKARI Observer s Web The AKARI Observers Web pages contains some additional information and data useful for the observers including links to the user support tools http www ir isas jaza jp AKARI Observation for Japanese amp Korean Open Time users http akari esac esa int for the ESA Call for ESA Open Time Users Helpdesk Any questions and comments on AKA RI observations and user support shall be addressed to the AKARI Helpdesks iris_helpQir isas jaxa jp for Japanese amp Korean Open Time Users http akari esac esa int esupport for ESA Open Time Users AKARI Observer s Manual Chapter 2 Mission Overview 2 1 The AKARI Mission AKARI previously known as ASTRO F is the second Japanese space mission for infrared astronomy It was launched on February 21 2006 UT by JAXA s M V rocket The orbit is a Sun synchronous polar orbit with an altitude of 700 km and a period of 100 minutes pair of Stirling cycle mechanical coolers enabled a long cryogenic mission lifetime with only 170 litres of liquid Helium The liquid Helium boiled off on Aug
45. duling of observations We will therefore drop SMMJ030227 000653 from our target list The output from the visibility tool should be saved as an ASCII file as it will need to be uploaded as part of the final submission process for our proposal 56 AKARI Observer s Manual Batch Query Interactive Query Check that no input file is given in the Batch Mode entry If there is please reload this page AKARI Visibility Batch Query Start Thu May 15 14 04 47 2008 CEST 43 1844 16 4057 0 4 4 2 J 2000 03 02 27 73 00 06 53 5 ID 1 SMMJ030227 000653 235 2299 61 8905 12 12 24 2 J 2000 16 36 39 01 40 56 35 9 ID 2 SMMJ163639 405635 148 1547 57 2310 9 12 21 2 J 2000 12 35 49 44 62 15 36 8 ID 3 SMMJ123549 621536 336 3477 10 1152 1 8 9 2 J 2000 22 17 33 91 00 13 52 1 ID 4 SMMJ221733 001352 AKARI Visibility Batch Query End Thu May 15 14 04 47 2008 CEST Figure 1 2 2 Results from the Visibility Tool in batch mode The result shows the total number of allocations possible during Phase 3 of the AKARI mission Each target is listed by position in Ecliptic coordinates visibility in Phase 3b1 2008 Oct 15 2009 Apr 11 179d Phase 3b2 2009 Apr 12 2009 Oct 14 186d and the total visibility in Phase 3 2008 Oct 15 2009 Oct 14 365d The original user input is shown on the right Vere Version 1 1 June 12 2008 57 A 2 3 The Choice of Observation
46. e measured extinction and SFR put a strong constraint on the SED model which is used to investigate the evolutionary phase of starbursts linking them with the formation of spheroidal systems Current measurements of the near infrared spectra of dusty starbursts have been limited to low redshift studies of local ULIRGS Veilleux 1997 Murphy et al 1999 Dannerbaur et al 2005 Our targets for the spectroscopy are the powerful Hy drogen recombination lines Paschen alpha at 1 875 micons and Paschen beta at 1 282 microns Observations of the Hydrogen recombination lines in local ULIRGs Dannerbaur et al 2005 have derived high Paschen alpha luminosities consistent with the predominant power source within these galaxies being star formation rather than accretion from an AGN Observations of a sample of higher redshift sources can test this measurement as a function of redshift Note that at low redshifts z lt lt 1 both of the Hydrogen recombination lines lie outside the IRC grism observation window 2 5 lt A lt 5 um For Paschen alpha the observable redshift range would be 0 3 lt z lt 1 7 while for Paschen Beta it would be 0 95 lt z lt 2 9 The target galaxies are summarized in Table 1 2 1 Table 1 2 1 Target sources for spectroscopic observations with AKARI Name Equinox R A Dec SMMJ030227 000653 J 2000 03 02 27 73 00 06 53 5 SMMJ163639 405635 J 2000 16 36 39 01 40 56 35 9 SMMJ123549 621536 J 2000 12 35 49 AA 62 15 36 8 SMMJ221
47. e spectroscopy data It also includes distortion correction of the image Sec tion 4 2 1 e There may be confusion from nearby targets in the case of observations in crowded re gions Currently these are not decomposed but rather masked in the overlap region for the measurements e Measurement of the spectrum is carried out in an aperture on the spectroscopic image The software attempts to fit an aperture automatically but the user may want to adjust this step interactively The tools are written in IDL 5 1 3 Phase 3 data Phase 3 data in the near infrared channel suffer a number of hot pixels significantly Also the dark current is no longer negligible The operation sequence of phase 3 is different from that in phase 2 in taking the dark current measurements before and after the celestial observations The associated dark measurements will be provided for the dark subtraction rather than the super dark data provided in phase 2 data package Appendix A AKARI Cookbook for Post Helium Phase 3 mission Open Time observations A 1 Introduction In order to aid observers with the preparation of proposals for Phase 3 Open Time we present in this section three worked examples for observation and submission of Open Time proposals with AKARI We show 1 IRC Spectroscopy of distant galaxies with the NG grism in the point source aperture 2 IRC Spectroscopy of a galactic target 3 IRC Near infrared imaging of extragalactic fields
48. ecognized for the NIR data They are noticeable only when bright sources are in the field of view For details please refer to the IRC Data Users Manual Version 1 1 June 12 2008 35 4 2 2 Detector system Hot Pixels The number of hot pixels increased dramatically in phase 3 They are now about 10 of the total pixels and are more concentrated in the slit spectroscopy area Figure 4 2 4 Development of software that treats these hot pixels is now in progress Observers are strongly recommended to perform redundant observations Figure 4 2 4 Dark frame images in phase 2 a and phase 3 b in the same ADU scale Linearity The well capacity of the NIR array is reduced by a factor of 5 6 in phase 3 compared to that in phase 2 because of the lower bias voltage used for phase 3 to reduce the number of hot pixels Observers should be aware of the dramatic reduction of the saturation level in phase 3 Observations of bright sources will not provide meaningful data although they will not make an aftereffect and thus will not be prohibited The linearity correction below the saturation level set by the well capacity will be made in the pipeline data processing 36 AKARI Observer s Manual 4 3 The IRC Instrument Operation 4 3 1 Pointed Observations Exposure cycle The minimum observation unit of the IRC is called an exposure cycle An IRC pointed observa tion consists of an n times repeated exposure cycle with operations such as a filter
49. ep Dithering of IRC imaging Use of the Micro scan is defined in the AOT and observers are not allowed to change it telescope attitude The IRC waits for notification from the AOCS and then starts an exposure This waiting time will be a dead time for observers The dead time for Micro Scan operations is typically about 30 sec and 40 50 sec It is noted that the actual stabilization time varies depending on the given condition These dead times are taken into account in the AOTs of the IRC and the corresponding sensitivity estimates No pointing reconstruction using the Focal Plane instruments is planned for the pointed observations The users will receive position information from the G ADS Since the source of the pointing uncertainty is the alignment of the telescope and the AOCS it is expected that the accuracy will be improved as the analysis progresses The users can refine the position using the data themselves for the IRC imaging observations Due to the trouble encountered at the start of the mission the TFSS is not used in the atti tude control This leads to an attitude control heavily relying on the Star Trackers thus imposing additional constraints in the pointed observations Pointed observations requiring maneuvering in the South Atlantic Anomaly SAA are not allowed In addition pointed observations in an area where few stars are detectable by the Star Trackers will not be executed 22 AKARI Observer s Manual 3 3 Mission Phas
50. es The mission lifetime of AKARI is divided into three observation phases excluding the perfor mance verification PV phases Phase 0 PV Phase The first month after the jettison of the aperture lid was assigned to the PV phase In this period a check out of the spacecraft system and the Focal Plane Instruments was made the in flight performance was evaluated and the initial calibration of the Focal Plane Instruments was carried out Test observations were also performed This phase lasted from April 13 2006 to May 8 2006 Phase 1 The first half year during which AKARI scanned the entire ecliptic longitude is referred to as Phase 1 In this period the Large Area Survey Programmes namely the All Sky Survey and the NEP LMC pointing surveys were carried out with highest priority Some Mission Programme observations were also performed Phase 2 This phase continued until 2007 August 26 when all liquid Helium evaporated Pointed observations of Mission Programmes and Open Time proposals were performed as well as supplemental scan observations to complete the All Sky Survey Phase 3 After the boil off of the liquid Helium the mechanical coolers will keep the temperature low enough to observe with the IRC NIR camera Phase 3 where only the IRC NIR camera is operated will continue until any on board instruments the NIR camera itself mechanical coolers etc cease to function The performance verification observations for phase 3 will be
51. g central stars Our first target is NGC7027 a very well known bright planetary nebula with a rich spectrum that has previously been observed by ISO Bernard Salas et al 2001 The second target is the fainter SMP83 planetary nebula in the Large Magellanic Cloud also observed by Spitzer Bernard Salas et al 2004 We will perform both high and lower resolution slit spectroscopy in the near infrared range which is unique to AKARI since Spitzer has no capability in this wavelength range The target positions are given in Table 1 3 3 Table 1 3 3 Suitable Planetary Nebula for Phase 3 spectroscopic study with AKARI Name Equinox RA Dec NGC7027 J 2000 21 07 01 7 42 14 11 0 SMP83 J 2000 05 36 21 0 67 18 14 0 A 3 2 Target Visibility Using the Visibility Tool to check the availability of our targets entering the coordinates using the interface in Fig1 2 1 we find that both targets have reasonable visibility The result of the Visibility Tool for is shown in Figure 1 3 8 and 1 3 9 for NGC7027 and SMP83 respectively Figure 1 3 8 shows that NGC7027 is visible only twice from October 2008 to April 2009 and a further 13 times in the latter half of Phase 3 April 2009 October 2009 This low visibility is mainly due to conflict with the SAA even given the reasonable ecliptic latitude Note the much higher visibility of SMP83 shown in Figure 1 3 9 due to its location almost on the South Ecliptic Pole at an ecliptic latitude of 87 degrees co
52. get list is shown in Table 1 4 7 A 4 5 Target List Validation The Target List syntax is validated in an identical manner to the previous imaging example The target list will also be automatically validated when we upload it during the final proposal submission stage so there is no need for us to save the output of the Validation Check Tool at this stage 74 AKARI Observer s Manual A 4 6 Duplication Check Tool Duplicate observations are decided on a basis of position instrument AOT and the number of pointings This tool returns all IRC observations within a radius of 5 arcmins from the requested targets which are either executed in the cold phase Phase 1 and 2 or are in the blocked target list for Phase 3 Putting our target list into the Duplication Check Tool and selecting summary for the out put we find that indeed there is a conflict of position or instrument for all of our observations in the HDF field see Figure 1 4 14 and the TAC will have to look into the scientific justification to decide whether our observation is unique The output from the Duplication Check tool should be saved as an ASCII file as it will need to be uploaded as part of the final submission process for our proposal Version 1 1 June 12 2008 75 Query target lia SAP A 9 BY C 9 DA tota 27 search radius 5 000 arcmin 3 targets in your list are duplicated with the blocked target list ID RA Dec MT Target name Result 1 47 750
53. grees In the pointing mode the telescope can point at an area of the sky along the scan path for up to 10 minutes with the total cost of 30 minutes including maneuver for the operation Observations in phase 3 will be carried out only in pointing mode The survey mode satellite operations will however still be conducted as designed Fine control of the observing position Ithe direction perpendicular to the scanning in scan direction 17 18 AKARI Observer s Manual in a pointing operation is possible Observations in the pointing mode are defined by a set of Astronomical Observation Templates AOT see Sections 4 4 The satellite Attitude and Orbit Control System AOCS has the capability of determining controlling the absolute attitude to an accuracy of 30 arcsec The dominant source of the pointing uncertainty is the alignment of the focal plane axis with respect to the AOCS reference frame on the bus module and its time variation due to thermal distortion of the spacecraft Table 3 1 1 summarizes the nominal operation parameters and expected performance of the AKARI AOCS for astronomical observations Table 3 1 1 AKARI AOCS Specifications Absolute Pointing Control Accuracy 30 arcsec Scan Speed Stability in scan lt 0 1 per cent Scan Speed Stability cross scan 3 x 1075 arcsec min Pointing Stability lt 1 arcsec min peak to peak Version 1 1 June 12 2008 19 3 2 Attitude Operation Modes for Observations 3 2 1 S
54. hase 2 Version 1 1 June 12 2008 31 4 2 Flight performance in phase 3 4 2 1 Optics Field of View FoV The FoV of the NIR is different for different filters depending on the alignment of the filters A summary is given in Table 4 2 3 Table 4 2 3 NIR camera FoV sizes FoV arcmin N2 9 3 x 10 0 N3 9 5 x 10 0 N4 9 5 x 10 0 Point Spread Function PSF The performance of the AKARI telescope in phase 2 was derived to be diffraction limited at 7 3 um and it was confirmed that the image quality was degraded by 10 20 in phase 3 Thus the PSF is more extended than the diffraction limits in the NIR camera Table 4 2 4 shows the preliminary results of the measurements of Full Width Half Maximum FWHM of the PSF for the imaging bands of the IRC cameras in phase 3 Table 4 2 4 Preliminary values of Full Width Half Maximum FWHM of the PSF for the IRC NIR imaging bands for phase 3 D 2 qty HON R we Chromatic Aberration The NIR camera has chromatic aberration of 0 3 0 4 mm which is in fact larger than the designed value The most likely cause is the uncertainty of the optical characteristics of the elements under cryogenic temperature The mean amount of aberration is comparable to that of the diffraction limited optics at 2 um and thus effects the image quality Optical Transmittance The throughout transmission functions RSRF Relative Spectral Response Function of the IRC NIR broad band filters a
55. he near infrared observations in Phase 3 with the previous results in Phase I amp II we may move some way to constraining the energy budget of the Universe into the contributions from star formation and black hole accretion For our program we will chose a set of well known fields where there is already a lot of follow up data including the Phase I and II observations with AKARI These are the ISO MARANO field UKIDSS UDS field the COSMOS field the HDF N field and the ISO southern ELAIS field These fields are summarized in Table 1 4 6 Table 1 4 6 Extragalactic target fields for observations with AKARI Name Equinox R A Dec ISO MARANO J 2000 03 11 00 0 54 45 00 0 UKIDSS UDS J 2000 02 21 20 0 04 30 00 0 COSMOS J 2000 10 00 28 60 02 12 21 01 HDF N J 2000 12 36 49 9 62 12 58 0 ELAIS S1 J 2000 00 38 30 0 44 00 00 0 Version 1 1 June 12 2008 71 A 4 2 Selection of Target Field and Target Visibility A Visibility Tool is provided that gives an approximate estimation of the open time visibility of the target field during the Phase 3 of the AKARI mission The available allocation for Open Time observations corresponds to around 6 pointings every day or almost a degree interval on the ecliptic longitude Visibility is a strong function of ecliptic latitude and observations requiring very deep imaging and or wide area mapping should choose their fields very carefully to avoid disappointment Targets are input into the Visibility Tool
56. ic field have worked to establish the observing programmes In total 16 Mission Programmes are now assigned The data will be used by the team members for a one year prioritized period and then will be opened to the public The MP observations are regarded as the legacy of the AK ARI mission Open Time Programmes OT 30 per cent of the total pointing opportunities are available to the general research community Two thirds of the opportunities 20 percent of the total are reserved for Japanese Korean astronomers and 10 percent are for the ESA member countries see document Call for Observing Proposals Policies and Procedures for more details 16 AKARI Observer s Manual 2 6 References The following papers in the special issue of the Publications of the Astronomical Society of Japan PASJ give detailed information on the AKARI mission as well as AKARI instru ments They describe the in orbit performance in the cryogenic period and are available at http pasj asj or jp v59 v59sp2 html The performance of phase 3 is described in the present manual as well as on the web Mission Overview The Infrared Astronomical Mission AKARI Murakami H et al 2007 PASJ 59 S369 Cryogenics Flight Performance of the AKARI Cryogenic System Nakagawa T et al 2007 PASJ 59 S377 Telescope In Orbit Focal Adjustment of the AKARI Telescope with Infrared Camera IRC Images Kaneda H et al 2007 PASJ 59 S411 FIS The Far Infrared
57. ice of Observation Mode o e 65 A 3 4 Preparation of Target List o e e 66 A 3 5 Target List Validation soara g oaa aa aa e aa ia ii ae oR i 68 A 3 6 Duplication Checker oaoa a 68 A 3 7 Submission of Proposal s wss a s ecs i aa aoee a S ee E 68 A 4 Example 3 Near infrared imaging of extragalactic fields with the IRC 70 A 4 1 Scientific Background sise a ee a aa ie ae a a a e a a ee ei 70 A 4 2 Selection of Target Field and Target Visibility oo oaoa aa 71 A 4 3 The Choice of Observation Mode o e e 71 A 4 4 Preparation of Target List o e e e 72 A 4 5 Target List Validation e e 73 A 4 6 Duplication Check Tool o 02020002 eee eee 74 AAT Submission of Proposal sbe dos a sae pica e 76 Chapter 1 Introduction 1 1 Purpose of this document This AKARI Observer s Manual is issued as the reference for AKARI observers for observation planning and the preparation for the data analysis for the post Helium mission hereafter called phase 3 The document covers the specifications of the satellite and the instruments their perfor mance flight operation plan including definitions of the Astronomical Observation Templates AOTS and a brief desscription on the scope of data analysis It contains the most up to date estimates of the detection limits of the instrument based on the phase 3 performance evaluation observations carrie
58. is worse by a factor of 2 than in phase 2 The factor of 2 was derived taking into account the degraded PSF and noise level in phase 3 which provides the best estimate at the present The detection limit for diffuse extended source is estimated from the point source detection limit divided by the area given by the FWHM of the PSF Table 4 2 4 Repeating an observation of the same region with the same AOT is supposed to improve the sensitivity by a factor of y n where n is the number of pointing opportunities Since the number of hot pixels in the NIR detector is dramatically increased in phase 3 redundant observations are strongly recommended The saturation limits are given as the flux level at which the detector signals deviate from linearity by 10 per cent In fact it is a rather rapid change from these levels to the absolute saturation and it is reasonable to use these levels as the saturation limits The saturation limits are the same for all the imaging AOTs IRCZO IRCZ2 and IRCZ3 The saturation limits for a short exposure are given in Table 4 4 6 Table 4 4 6 Saturation limits for IRC imaging modes TT N2 0 13 NIR N3 0 11 N4 0 07 40 AKARI Observer s Manual 4 4 2 IRCZO Deep Imaging Mode Recommended Usage IRCZO mode is prepared for deep imaging observations of high visibility regions where more than 6 pointed observations can be easily obtained Description The mode is designed to maximize the exposure time
59. ith a sampling rate of about 50 Hz The seven detectors are sampled almost simultaneously As the satellite scans the sky stars cross the detectors in the in scan direction one after an other The detection interval between a pair of two horizontal detectors placed in parallel defines the scan speed and the interval between the tilted and horizontal detectors can be converted to the cross scan position The two FSTS s located in opposite corners provide information on the roll angle of the Focal Plane with respect to the scan direction as well as a redundancy for the star detection The absolute positional information is given by comparing the detection information with the position reference catalogue The pointing reconstruction using the FSTS assumes all sky survey operation mode The FSTS is not used in phase 3 2One of the four elements is known to be dead The effect of this loss to the pointing reconstruction is expected to be small Version 1 1 June 12 2008 15 2 5 The AKARI Observation Programms in Phase 3 Phase 3 Observations with AKARI can be divided into the following three categories Director and Calibration time DT 10 percent of the pointed observation opportunities are reserved for calibration and director s time Mission Programmes MP 60 percent of the pointed observation opportunities are allo cated to the AKARI team members as a kind of guaranteed observation time Specific working groups in every scientif
60. itude A set of reaction wheels RW control the spacecraft attitude with the help of Magnetic Torque Rods MTQ In the case of any very large required motion a set of thrusters may be used In the initial phase of the mission the TFSS were found not to detect the Sun properly This was overcome with a new version of the on board software for the attitude and orbit control subsystem making use of the Star Trackers STT A RW A STT B RW B TESS AOCU RW C IRU A RW D OCP A IRU B OCPB MTO X NSAS MTO Y OCP C CES A MTO Z CES B GAS CS20Nx4 ACM CS 3Nx4 Sensors Data Handling Unit Drivers Figure 2 2 2 Block diagram of the AKARI attitude determination and control system 8 AKARI Observer s Manual 2 2 3 Cryogenics Scientific instruments are all stored in the cryostat and were maintained at cryogenic tempera tures by 170 litres of super fluid liquid Helium with the help of two sets of Stirling cycle coolers The near infrared instrument is operated with the mechanical coolers after the liquid Helium boil off AKARI is operated with the Sun shield always directed to the Sun The cryostat is covered by silver coated film that reflects visible light but radiates in the infrared The Scientific Instrument Assembly SIA namely the telescope and the Focal Plane In struments FPI are thermally shielded by two
61. lement for the NIR camera Table 4 4 12 Dispersion element selection in IRCZ4 NP NG The second parameter gives the position reference for this AOT It is more complicated than other AOTS because of the presence of the slits Np and Nh are intended to be used with the NG and others with the NP although all the position reference parameters are allowed both for NP and NG It should be noted that for point sources Nh or Ns should not be used The absolute pointing accuracy of AKARI does not guarantee that the intended point source be located on the narrow slit Also usage of Nc with NG for slit less spectroscopy is not recommended unless observers assure that the target will not be confused by surrounding faint sources Version 1 1 June 12 2008 Table 4 4 13 Target position parameter for IRCZ4 Description The target position is placed at the center of the NIR FoV The target position is placed at the common slit of the NIR and MIR S The target position is placed at the point source aperture of the NIR The target position is placed at the high resolution slit of the NIR 47 48 AKARI Observer s Manual 4 4 9 Expected Performance Detection Limits Figure 4 4 8 shows the 50 detection limits for point sources with NP and NG in low sky back ground regions assuming 8 exposure cycles in a pointing opportunity Note that for high back ground regions such as star forming regions the detection will be limited by background fluctu
62. main field of view or one of the aperture slits with which we want to observe We intend to observe with the NG grism in the point source aperture so we can fix the first parameter as b and the second parameter as Np i e b Np In the following field we input the number of pointings for each AOT for our case this will be 10 for each target We then have to prioritize our targets AKARI Open Time Observations are divided into 3 priorities A B C Our A amp B targets barring any unforeseen events should be observed while the priority C targets should be considered as back ups In our target list the number of priority A B targets should be around the same and the number of C target should be roughly A B For our observations therefore we allocate one priority A target one B and the remaining target as priority C Note It is extremely important to include an ample number of C targets even though we have not done so in this particular example as AKARI scheduling is tough and if there are not enough back up targets you may lose your allocation A good size number of priority C targets is also necessary to replace any higher priority targets that may incur possible duplication conflict see the discussion on duplication later with Mission Program targets AKARI supports the concept of symbiotic observation This option in the penultimate field of the target list entry field 10 enables the observers to specify that more than 2 poin
63. mpared to NGC7027 at a more moderate ecliptic latitude of 55 degrees This shows the huge advantage in scheduling gained by targets at extreme latitudes The output from the visibility tool should be saved as an ASCII file as it will need to be uploaded as part of the final submission process for our proposal 64 AKARI Observer s Manual 3 Open Time Visibility Tool Figure 1 3 8 Results from the Visibility Tool in single target mode for the planetary nebula NGC7027 The result shows the total number of allocations possible during Phase 3 of the AKARI mission Each target is listed by position in Ecliptic coordinates visibility in Phase 3b1 2008 Oct 15 2009 Apr 11 179d Phase 3b2 2009 Apr 12 2009 Oct 14 186d and the total visibility in Phase 3 2008 Oct 15 2009 Oct 14 365d The original user input is shown on the right 339 5082 87 5682 50 50 100 2 J 2000 84 0875 67 3039 Figure 1 3 9 Results from the Visibility Tool in single target mode for the planetary nebula SMP83 Version 1 1 June 12 2008 65 A 3 3 The Choice of Observation Mode The estimated sensitivity of the IRC in slit spectroscopy mode during the cold phase of the IRC mission was around a few x 107 Wm gt For Phase 3 we can expect at least a factor of two degradation in this sensitivity to for example 5x 10718 Wm The near infrared spectra of planetary nebula are rich Hydrogen and Helium lines and some ions such
64. observes a target with all three filters of each camera This mode is not recommended for sky areas of low visibility where two pointed observations cannot be guaranteed Description IRCZ3 is similar to the IRCZ2 mode but differs in the number of filters and dithering positions in one pointing opportunity The target sky position is observed by three filters Instead only one Micro Scan 2 dithered images is applied for each band To obtain reliable results it is recommended to have sufficient redundancy by observing the same sky position at least twice on different orbits The net exposure time per filter is thus 2 9 of the IRCZO Parameters IRCZ3 uses all filters of the IRC NIR channel The advantage of using this mode over IRCZ2 has to be carefully considered from the scientific viewpoint of each observation The position reference is fixed at the center of the NIR camera N Version 1 1 June 12 2008 45 4 4 7 Expected Performance Detection Limits Expected 5o detection limits of the IRCZ3 observing mode are given in Table 4 4 11 assuming 2 exposure cycles per filter in a pointing opportunity Table 4 4 11 Detection limits for IRCZ3 dy MJy sr N2 39 0 076 N3 39 0 075 N4 38 0 075 Saturation Limits The saturation limits of the IRCZ3 mode are given in Table 4 4 6 46 AKARI Observer s Manual 4 4 8 IRCZ4 Spectroscopic mode Recommended Usage IRCZ4 is prepared for spectroscopic observations with the IRC
65. on High sensitivity near infrared spectroscopy free from disturbance of the terrestrial atmosphere can be applied for studies in various astronomical objects Version 1 1 June 12 2008 11 2 4 Focal Plane Instruments 2 4 1 Specification Overview Two scientific instruments are placed in the Focal Plane of the telescope the Far Infrared Sur veyor FIS and the Infrared Camera IRC In addition two sets of Focal Plane Star Sensors FSTS are installed for observing guide stars in the Near Infrared band J band for pointing reconstruction during the survey observations In phase 3 only the near infrared channel of the IRC is available for observations The whole payload capability is reported below for historical reasons The FIS is equipped with two sets of two dimensional detector arrays The Short Wavelength channel SW 50 110 um uses two monolithic Ge Ga arrays of 20 x 3 and 20 x 2 pixels while the Long Wavelength channel LW 110 180 um has a stressed Ge Ga array of 15 x 3 15 x 2 pixels Each of the four arrays corresponds to a different wavelength band The pixel sizes are 27 and 44 arcsec respectively The IRC consists of three independent cameras the NIR 2 5 um the MIR S 5 13 um and the MIR L 13 26 um The NIR camera has a 512 x 412 pixel InSb array of which 100 x 412 pixels are dedicated for slit spectroscopy The two MIR cameras use 256 x 256 pixel Si As detectors The wavelength range and resolving power pr
66. ons 17 3 1 Orbit and Observing Attit de lt so sa se swi aweka pa naan i ee I7 3 2 Attitude Operation Modes for Observations o oo aoo a e so 19 32 1 Survey Mode ss s es moma wa e bea aein e a N ER ae ee e 19 322 Pointing Mode gt pa secs ane ios AR Aer o 544446 oe eee SS a A 19 3 9 Mission Phases a sos gaa a a ce a de A a N EE 22 34 Sky AE oi AE AE o Ri A we a a es 23 4 IRC Infrared Camera 25 Ai Hardware Specifications e a aa ra e 26 AV OVervi W kiss css cra ea a ARA 26 AAD OPUS 5 2 8 pues sra a a ES 27 4 1 3 Filters and Dispersion Elements 2 0220004 28 4 1 4 Field of View FOV 2 2 4 presi OHO RO Se FG Aw bre pe os 29 4 1 5 Slits for Spectroscopy ee 29 4 1 6 Detectors se MR oa ka Sasha bom a sa 30 4 2 Flight performance in phase3 0 0 00000 eee ee 31 ADA OPUCS he s ma eoe e a e aa ads e 31 4 2 2 Detector system lt y w sac Ad e 35 4 3 The IRC Instrument Operation e s soo eae e 36 Version 1 1 June 12 2008 iii 4 3 1 Pointed Observations 2 0 0 00 ee ee 36 AA The IRC AOTS 2446 4 068484 e 8a 4a wk Pea ee ee ee eee 38 4 4 1 Detection Limits and Saturation Limits General Remarks 39 4 42 IRCZ0 Deep Imaging Mode 2 000000 2 ae 40 4 43 Expected Performance e 41 4 44 IRCZ2 Imaging and Spectroscopy with Two Filters or Filter and Prism 42 4 45 Expected Performance e 43 4 4 6 IRCZ3 Imaging with Three Filte
67. ovided by the scientific instruments are shown in Figure 2 4 5 The spatial resolution and the Field of View FoV of the instruments are summarized in Figure 2 4 6 100 NEER a EE MG en ps i FTS 100 ism amp Grism z 10 Wide band Photometry y Wide band Imaging 1 10 100 Wavelength um Figure 2 4 5 The wavelength coverage and resolving power of the AK ARI instruments The SW detector was manufactured by NICT 12 AKARI Observer s Manual de IRC FIS 1000 A AE gt a 5 ES RE eee Field of View q Field of View 1 00 cross scan 3 2 10 A x Telescope Limit Pixel Size MEE SEMI 1 10 100 Wavelength um Figure 2 4 6 Pixel size and field of view FoV of the AKARI on board instruments Version 1 1 June 12 2008 13 2 4 2 Focal Plane Layout Figure 2 4 7 shows the Focal Plane layout projected onto the sky There are three light entrances to the instruments one for the FIS and two for the IRC The two instruments essentially can observe simultaneously but they see different areas of the sky as shown in the figure Therefore observations of a sky position with different aperture have to be made on different orbits The incident infrared radiation coming into the FIS aperture is divided into two spectral domains by a dichroic beam splitter as a result of which the FIS SW and LW detector arrays observe almost the same sky position Similarly the NI
68. p is to upload the Target List which will be auto matically verified syntax only on uploading Following this we will be required to upload the results we saved from the output of the Visibility Tool Duplication Check Tool and Instrument Performance Tool respectively Once all these files have been uploaded we will have to enter the specific proposal information name address telephone number etc and general proposal information Co Is category title abstract The Scientific Justification must be submitted in PDF format and should not exceed 6 pages in total including scientific rationale objective references figures and tables and technical feasibility of the proposal A confirmation page of the submission is created automatically Shortly after users will receive a formal confirmation by e mail with the cover page of their proposal
69. re shown in Figure 4 2 2 The filters and optical components as well as the detector response are taken into account to produce the curves These RSRFs can be These RSRFs have been prepared in collaboration with Dr Martin Cohen to ensure a common calibration of the IRC with other missions and ground based instruments including Subaru COMICS in the framework of the absolute calibration network provided by him and his colleagues 32 AKARI Observer s Manual directly integrated over spectra given as F to obtain the in band fluxes synthetic photometry These RSRFs are derived for phase 2 observations Minor changes are expected in phase 3 Figure 4 2 3 shows the RSRFs of the dispersion elements given per photon These data are also available in digital format on the Observer s support web pages Version 1 1 June 12 2008 33 o O eN Co Relative Response o N o nm O Wavelength um Figure 4 2 2 The Relative Spectral Response Function of the IRC NIR Camera for Fy O Co NP NG Relative Response O O a gt o o N O 1 2 3 4 5 6 Wavelength um Figure 4 2 3 The Relative Spectral Response Function of the IRC NIR dispersion elements per photon 34 AKARI Observer s Manual Distortion Image distortion of the IRC NIR camera is negligible The difference in the pixel scale in the X and Y directions is corrected in the data pipeline processing Ghosts There are several ghost patterns r
70. rget List Validation Once the target list has been completed we can proceed towards the submission stage However there are still a few steps to complete We should run our target list through both the Target List Validation Tool and then we need to submit the target list to the observation Duplication Check Tool The Target List Validation Tool takes a target list and makes a simple check on the target list format e g correct number of fields AOT in expected form etc It does not perform any test on the scientific validation e g on position or sensitivity etc We can submit the Target List as a batch file in a similar manner to the Visibility Tool as in Figure 1 2 4 in fact this target list format is accepted by all tools during the submission process Figure 1 2 5 shows the output of the Target List Validation Tool Any errors are highlighted in red and a summary given at the bottom of the output In this case an AOT has been input incorrectly and has been highlighted The target list should therefore be edited and re submitted The target list will be automatically validated when we upload it during the final proposal submission stage so there is no need for us to save the output of the Validation Check Tool Batch Query Target Listinput Choose File mytargetlist txt Submit Reset Figure 1 2 4 Input to the Target List Validity Checker 2 SMMJ163639 405635 J2000 16 36 39 01 40 56 35 9 IRCZ4 b Np
71. rs 2 44 AA Expected Performance d e 4 62 54 65 a Pe a e 45 4 4 8 IRCZ4 Spectroscopic mode es se ee aona won a eee eee 46 4 4 9 Expected Performance 0 0000 eee ee eee 48 4 5 Notes and Restrictions for the IRC Observations 0 4 50 5 Data Reduction and Products 51 Ball Basie Policy sas lt oc oe A ORE wap we ei EE EE OE e 52 5 1 1 IRC Data Reduction AOT IRCZO Z2 Z3 es adea sainga h a a E a 52 5 1 2 IRC Data Reduction AOT IRCZ4 aaau a 52 S3 Phase s8 data sa soroa ate 40 Ne baa Oi oe a e RR EER a 52 A AKARI Cookbook for Post Helium Phase 3 mission Open Time observa tions 53 ALL Introductionis 4 erpi ae E A A woe are edo A EG N eo 53 A 2 Example 1 Spectroscopy of distant galaxies with the NG grism in the point SOUTG 8pertur ss ER eee e BR OR ee ee ee ee e EE Ri 54 A 2 1 Scientific Background oe a si eare a d amoo o 54 A 2 2 Selection of Targets and Target Visibility 55 A 2 3 The Choice of Observation Mode oaa aa e 57 A 2 4 Preparation of Target List ioo ei ee a a a R a e 58 A 2 5 Target List Validation osasi ica gaa dik e 0002 ee ee a 60 A 2 6 Duplication Check i a 2 0 0 0 0000 ad ee ee 61 A 2 7 Submission of Proposal 0 0 0002 ee ee 62 A 3 Example 2 Spectroscopy of Planetary Nebulae with the IRC 63 A 3 1 Scientific Background e 63 A 3 2 Target Visibility sos 644346086400 Gee A RR GE Re 63 A 3 3 The Cho
72. rvation opportunities were open for general users in Phase 2 in Japan Korea and ESA related countries via parallel peer reviewed Call for Proposals Many international collaborations are ongoing with the AKARI project The European Space Agency ESA supplied a ground station operated by ESOC and ESAC carries out the pointing reconstruction of the All Sky Survey observations ESAC also handles the user support for the European Open Time observing programmes A consortium of Imperial College University of London the Open University University of Sussex and SRON Groningen with University of Groningen IKSG consortium participates on the data reduction of the FIS All Sky Survey Seoul National University representing the Korean community also joins the data reduction activity Several collaborations at the personal level are also ongoing especially on the celestial calibrators AKARI Observer s Manual 2 2 Satellite Figure 2 2 1 shows the overall structure of the AKARI spacecraft The height is about 3 7 m excluding the aperture lid and the launch weight mass 952 kg The satellite consists of two parts the bus module and the cryostat The two parts are connected by a truss structure 2 2 1 2170 A Telescope Sun Shield y Stirling Cycle Cooler Star Trackers Focal Plane Instrument Electronics S band Antenna A Vv Z Son S OP O Thrusters Y s Earth Sensor y 0 6 Figure 2 2 1 An overall view of the
73. taset G ADS and detailed analysis together with the Focal Plane Star Sensor FSTS and IRC survey data The outline of the attitude determination process is summarized in Figure 3 2 2 The on board attitude analysis has an absolute error of 30 arcsec The main source of this error is the alignment uncertainty between the satellite AOCS and the telescope s focal plane The results of the on board analysis are downloaded to the ground with the sensor signal data The data is re analyzed by the G ADS for cross check and to prepare the initial pointing data for reconstruction At this stage the pointing data in the survey mode still has an error of 15 30 arcsec Then the data from the FSTS and the IRC survey are analyzed together with the initial pointing data for refinement pointing reconstruction The ESA European Space Astronomy Centre ESAC is in charge of the final pointing reconstruction The goal of the pointing accuracy after the reconstruction is 5 arcsec in scan and 7 arcsec cross scan during the survey This accuracy can be improved to 3 arcsec in scan and 5 arcsec cross scan when the survey is completed and all data are analyzed and reprocessed 3 2 2 Pointing Mode In the pointing mode AK ARI will observe a specific sky position Both imaging and spectro scopic observations with longer exposure times than the survey are possible A single pointed observation consists of four continuous operations Figure 3 1 1 right
74. ther hand it may reduce the accuracy in the determination of the reference wavelength position because of the dithering Parameters There are two choices for the filter disperser combination in this AOT as given in Table 4 4 9 The parameter a is set for imaging with N3 and N4 and b new for phase 3 is set for N3 and prism Table 4 4 9 Filter combination of IRCZ2 Parameter E Filter Prism N3 amp N4 N3 amp NP The FoV reference position is fixed at the center of the NIR camera N Version 1 1 June 12 2008 43 4 4 5 Expected Performance Detection Limits The expected 5d detection limits of the IRCZ2 imaging mode are given in Table 4 4 10 assuming 3 exposure cycles per filter in a pointing opportunity The NP mode 50 detection limit is shown in Figure 4 4 7 Table 4 4 10 Detection Limits for IRCZ2 uy MJy sr N3 31 0 061 N4 31 0 061 100 EA OOO OOOO 5 o Detection Limit mJy Oly 96 3 39 4 45 Wavelength um N Figure 4 4 7 50 detection limit for NP in IRCZ2 Saturation Limits The saturation limits of the IRCZ2 imaging mode are given in Table 4 4 6 For the NP mode it is estimated to be about 3Jy at 3 um However the saturation in the N3 mode will make it difficult to determine the reference wavelength position from the N3 image accurately 44 AKARI Observer s Manual 4 4 6 IRCZ3 Imaging with Three Filters Recommended Usage IRCZ3 is used for general purpose observing It
75. tings are required to complete an observation This may be set for example for observations at the same position but with different instrument configurations or for mapping large areas When this parameter is given however it will constrain the observation plan significantly and increases the risk that the observations will not be scheduled at all If we schedule any of our observations as symbiotic we would group them together with a Group ID number and an observational style Version 1 1 June 12 2008 59 Table 1 2 2 Target List for submission 2 SMMJ163639 405635 J2000 16 36 39 01 40 56 35 9 IRCZ4 b Np 10 A redshift 1 488 3 SMMJ123549 621536 J2000 12 35 49 44 62 15 36 8 IRCZ4 b Np 10 B redshift 2 2032 4 SMMJ221733 001352 J2000 22 17 33 91 00 13 52 1 IRCZ4 b Np 10 C redshift 2 5510 as 1 0 The second parameter being either o or a where o means one of the observation is acceptable and a means either all or none is acceptable For our targets we could still get useful information even with a partial observation so we do not want the extra constraint of symbiotic observation therefore we will leave the field blank not forgetting the comma field separator Finally any notes are appended on the end of each target list line Our final target list is shown in Table 1 2 2 60 AKARI Observer s Manual A 2 5 Ta
76. to identify each proposal The next step is to upload the Target List which will be automatically verified syntax only on uploading Following this we will be required to upload the results we saved from the output of the Visibility Tool and Duplication Check Tool respectively Once all these files have been uploaded we will have to enter the specific proposal information name address telephone number etc and general proposal information Co Is category title abstract The Scientific Justification must be submitted in PDF format and should not exceed 6 pages in total including scientific rationale objective references figures and tables and technical feasibility of the proposal A confirmation page of the submission is created automatically Shortly after users will receive a formal confirmation by e mail with the cover page of their proposal Version 1 1 June 12 2008 63 A 3 Example 2 Spectroscopy of Planetary Nebulae with the IRC In this worked example we consider a program to perform spectroscopy on a few Planetary Nebulae with the AKARI IRC instrument We will simulate the preparation of the proposal from scientific background to proposal submission A 3 1 Scientific Background We consider 2 planetary nebulae as a study for spectroscopy with AKARI These objects have extremely rich and highly ionized spectrum due to their hot central star Analysis of the spectra can give insight into the evolution and origin of the ionizin
77. ts near the ecliptic plane are visible by AKARI for only two days 30 orbits ie 14 4 revolutions per day in a half year at the most The Visibility Tool can be found on the AKARI Phase 3 AO page The visibility tool front end is shown in Figure 1 2 1 We have to provide a target list or a single pointing The input coordinates and equinox shall be in the format HH MM SS S for J2000 or in degrees for J2000 Ecliptic or Galactic Although it is not necessary to enter any information on the AOT into the Visibility Tool itself at this stage the visibility tool does take its input in target list format see table 1 2 2 The output for our target list is shown in Figure 1 2 2 which lists the query input on the right of the screen and the total number of allocations possible on the left position in Ecliptic coordinates visibility in Phase 3b1 2008 Oct 15 2009 Apr 11 179d Phase 3b2 2009 Apr 12 2009 Oct 14 186d and the total visibility in Phase 3 2008 Oct 15 2009 Oct 14 365d In our case three of our sources are observable for an adequate number of slots However one of our targets SMMJ030227 000653 is only observable on four opportunities In this particular case it is a combination of the low Ecliptic latitude and a significant number of pointing opportunities lost to interference from the South Atlantic Anomaly SAA This emphasizes the strong constraint on the visibility imposed by the orbit of AKARI on the sche
78. uplication Tool successfully The output from the Duplication Check tool should be saved as an ASCII file as it will need to be uploaded as part of the final submission process for our proposal Upload target list The Target List must be in CSV Comma Separated Value format DO NOT send ANY compressed files i e zip Izh hqx sit gzip and so on Reference Explanation of target list format Choose File _ mytargetlist txt Search radius 5 0 arcmin fix Figure 1 2 6 Input screen for the Duplication Check Tool The input is the target list as usual Query target list S 0 A 10 B 10 C 10 D 0 total 30 search radius 5 000 arcmin 0 targets in your list are duplicated with the blocked target list ID R A Dec AOT Target name Result 2 249 163 40 943 IRCZ4 b ND SMMJ163639 405635 A OK 3 188 956 62 260 IRCZ4 b Np SMMJ123549 621536 B OK 4 334 391 0 231 IRCZ4 b Np SMMJ221733 001352 C OK Command executed on 2008 05 15 22 31 50 JST Figure 1 2 7 Output from the Duplication Check Tool for our target list All our targets pass the Duplication Tool successfully 62 AKARI Observer s Manual A 2 7 Submission of Proposal After the duplication check we can finally submit our proposal via the web interface The pro posal submission has several stages and we will need to upload various output files saved from the tools we used earlier Each proposal has a 5 character abbreviation which will be used
79. urvey Mode The survey mode is not used in observations of phase 3 This section is left over for information In the survey mode AKARI performs a continuous scan of the sky The spacecraft spins around the Sun pointed axis once every orbit keeping the telescope pointed toward the opposite direction to the Earth see left hand of Figure 3 1 1 as a result the telescope traces a great circle with a solar elongation of 90 deg The orbital period of 100 minutes corresponds to a scan speed of 3 6 arcmins In Table 3 2 2 the specification and performance of the survey mode operation are summarized Table 3 2 2 Summary of Survey mode operation nominal Specification of Survey mode operation Survey Scan Speed 3 6 arcmins Survey In scan Stability lt 0 1 per cent Survey Cross scan Stability 3 x 107 deg sec 30 Pointing determination error goal On board lt 30 arcsec in scan and cross scan G ADS 15 30 arcsec in scan and cross scan Pointing Reconstruction During Mission lt 5 arcsec in scan lt 7 arcsec cross scan Pointing Reconstruction Post Mission lt 3 arcsec in scan lt 5 arcsec cross scan Based on the performance evaluation tests The accurate position of the survey scan path on the sky is determined during the pointing reconstruction processing There are three levels of the processing on board determination by the attitude and orbit control system AOCS on ground processing using the same da
80. ust 26 2007 After the liquid Helium exhaustion the telescope system is kept at about 40K by the mechanical cooler and observations at near infrared wavelengths are continued AKARI is equipped with a 68 5 cm cooled telescope and two scientific instruments namely the Far Infrared Surveyor FIS and the Infrared Camera IRC The FIS has two 2 dimensional detector arrays and observes in four far infrared bands between 50 and 180 um at cryogenic temperatures The IRC consists of three cameras covering 1 8 26 um in 9 bands with fields of view of approximately 10 x10 Both instruments have low to moderate resolution spectroscopic capability Only the near infrared channel 1 8 5 5 um is available for phase 3 observations A major goal of the mission is to carry out an All Sky Survey with the FIS and additionally with the IRC at 9 and 18 um The AKARI All Sky Survey will significantly surpass the previous all sky survey in the infrared by IRAS in both spatial resolution and wavelength coverage The results will be published as AKARI infrared source catalogues In addition to the survey observations AKARI allowed for dedicated pointed observations with both the FIS and IRC Five thousand pointed observations were performed in the cryogenic phase of the mission Many pointed observations are used for the legacy observations by the AKARI project team members Such programmes are referred to as Mission Programmes In addition 30 percent of pointed obse
81. ve to understand that the visibility of AKARI to observe a specific target is extremely limited In order to avoid the Earth light the satellite starts slewing back to the survey mode auto matically if the avoidance angle exceeds the limit This happens without notifying the instru ments to complete the observation As a result the very last part of some observation data may be lost in some unfortunate cases In Table 3 2 3 we summarize the specifications of the pointing mode The FoV is allowed to shift by a small amount in a pointed observation in the way summarized in Table 3 2 4 These fine control operations are all included in the AOTs and users do not have to con cern themselves with them An IRC observation uses Micro Scan for dithering See the AOT description page for more details The Micro Scan will cause a disturbance of the satellite attitude at the level of a few arc seconds Therefore each exposure has to be started after waiting for the stabilization of the Version 1 1 June 12 2008 21 Table 3 2 3 Summary of Pointing mode operation nominal Specification of Pointing mode operation Total operation time Maximum observation time Absolute accuracy of pointing 30 arcsec Cross scan Offset Pointing Stability lt 1 arcsec peak to peak in 1 minutes Based on the performance evaluation tests Table 3 2 4 Pointing adjustment during a Pointed observation Amount of shit Micro Scan 15 30 arcsec st
82. y simultaneously Reference positions for the AOT configurations for pointed observations are indicated in blue in Figure 4 1 1 Phase 3 imaging observations AOT IRCZO IRCZ2 and IRCZ3 have a unique reference position the center position of the NIR camera N Reference positions for spectroscopic observations AOT IRCZ4 are explained in the following section Slit MIR L 7 x0 4 Ls Scan Direction Telescope Axis Slit NIR 3 x1 Nh Slit NIR 1 x1 Np Slit NIR MIR S 5 x0 8 Ns 25 0 9 3 0 7 for N2 9 5 0 5 for N3 4 N4 9 1 for MIR S all bands Figure 4 1 1 Focal Plane layout of the IRC cameras Reference positions for pointed observa tions are indicated in blue 4 1 5 Slits for Spectroscopy The dispersion elements of the IRC are set into the filter wheel so that all the light in the FoV is dispersed A spectrum is obtained in the direction parallel to the scan path in scan direction which runs along the vertical direction in Figures 2 4 7 and 4 1 1 Slits are provided for each camera Figure 4 1 1 in order to avoid contamination by nearby sources diffuse radiation The slits are primarily designed for extended sources and it should not be assumed that they can be used to guide a point source into the slit except for the NIR camera which has an aperture for point sources The slit for the NIR camera consists of three parts of different widths The left most closest
83. ycle A pair of short and long exposures are carried out for the NIR camera The upward arrows indicate the data read timing A pointed observation is carried out by repeating the exposure cycle with Micro Scans and filter changes inserted between them These operations cause dead time due to the operations themselves and stabilization of the satellite attitude The dead time is 20 80 seconds depending on the operation and the performance of the attitude control system Additional time for sending the data to the satellite s data processor DHU is also needed These operations and dead times are taken into account in the design of the Astronomical Observation Templates AOT section 4 4 During a pointed observation the IRC on board controller communicates with the Attitude and Orbit Control Unit AOCU via the DHU When the IRC requests a Micro Scan for dither ing it asks the AOCU to perform the operation The AOCU drives the satellite then waits for the stabilization When the AOCU decides that the satellite has stabilized with a preset criteria it sends back a signal to the IRC via the DHU to start the next exposure cycle This Version 1 1 June 12 2008 37 sequence continues until the AOT is completed If by some reason the attitude of the spacecraft exceeds the allowed range of the angle with respect to the Earth the AOCU stops the pointing mode attitude and returns back to the survey attitude regardless of the observation The IRC
84. ystem Observation Due to the severe visibility constraint observation planning for Solar System Targets requires additional procedures The following steps are suggested 1 Calculate the target position for the corresponding observation dates This can be done with NASA JPL s HORIZON system http ssd jpl nasa gov cgi bin eph by giving the condition of solar elongation angle as 90 1 deg 2 Use the visibility tool following the link from the Phase 3 AO page to check if the target is really visible at that position at that date 3 Create the Target List with the coordinates The corresponding observing date has to be given in the comment field of the Target List 4 Check the visibility again with the visibility tool 24 AKARI Observer s Manual Chapter 4 IRC Infrared Camera The Infrared Camera IRC on board AKARI is designed to perform deep imaging observations in pointed observing mode It s unique wide field coverage of 10 x 10 arcmin is ideal for survey type observations The IRC s low resolution spectroscopic capabilities in the imaging field are also well suited for multi object spectroscopic surveys In this section the description of the mid infrared channels is left over for reference in several places but only the near infrared channel is available for phase 3 observations The performance numbers given in this section were derived from observations in phase 2 Changes from phase 2 observations are indi

AKARI Observer`s Manual for the Post-Helium (Phase 3) - RSSD

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