PACS Photometry observing strategies - Herschel
Contents
1. PACS Photometry observing strategies ESAC June 2010 Bruno Altieri HSC amp Nicolas Billot NHSC page 1 NASA Herschel Scienc Se Center Preliminary remarks and Useful Links Documentation at HSC http herschel esac esa int Documentation shtml e HSpot User s guide http herschel esac esa int Docs HSPOT htmil hspot help html e PACS observer s manual http herschel esac esa int Docs PACS html pacs_om html http herschel esac esa int Docs PMODE html parallel_om html e Herschel Observer s manual http herschel esac esa int Docs Herschel html observatory htm e AOT release notes http herschel esac esa int AOTsReleaseStatus shtml e Herschel Reserved Observation Search Tool http herschel esac esa int Tools shtmlI HROST NHSC website _ https nhscsci ipac caltech edu sc e Documentation Page https nhscsci ipac caltech edu sc index php Pacs HomePage e Open Time 1 Proposals Page https nhscsci ipac caltech edu sc index php Proposals Proposals page 2 Bruno Altieri Nicolas BILLOT HSC June 2010 NASA Herschel Science Center HSpot User s Manual HSpot is remarkably simple and a user friendly piece of software Herschel Observation Planning Tool Launch version Astronomical Observation Requests AORs Position Type T G F Instrument Mode Intormatior Curation EJ Observations Target None Specified Total Duration hrs 0 0 Enable automatic u2. required sensitivity page 26 Questions HSC website http herschel esac esa int esupport e Where to find this presentation page 27
3. Angle from degrees 0 0 Angle to degrees 360 0 Cancel OK a __ EEE tL 600s penalty t u nhse NASA Herschel Science Center AOR Performance Estimate A O PACS Time Estimation Instrument performance summalt fnd Point Sour Point Sour Averaged Central ar Extended Extended Extended fiumi Flux SIN l f l f Surface SIN l j Density noise noise Brightness noise a Eu f imiy my gm My sr Miy sr Se nsitivity estimates 60 85 500 00 42 18 11 85 20 00 1 69 11 82 130 210 200 00 7 54 26 54 30 00 5 74 5 23 i e Ea E Eae een only for mini scan map mode Calibration time s 59 Target GBalact Instrument and observation overhead is 249 P u i Positifn 19 Details of AOR execution time 3 Observatory overhead is 180 New Targe Total time s 1179 2 E E EE Numberfof visible s PACS Time Estimator Messages Star tragker target More details here Confusion noise estimation summary Inst BI h I filt i Band Est l 0 Est l 0 Est l 0 Be ANE ee Sree um Contusion Noise Contusion Noise Contusion Noise 60 85 micrork band Level for Level for Level per Pixel ce ssaa Band Point Sources Extended Sources my r 5 J 85 micrdns ban UA u 9 im Miyis0 Confusion noise estimates 60 85 0 26 0 6762 0 17 Observ 130 210 7 85 4 3499 4 45 Source type and magping mode Fa 4 Update Confusion Noise Estimation Confusion Noise Estimator Messages Set the Obsefving Modes a E f 1 Don
4. Name required SIMBAD Resolve the Name the Name n ng ela is bi e Ss Oo G Target Visibility beta pic Fixed Moving Moving B kgr nd Coord Sys Equatorial J2000 Proper Motion 7 S gt 7 RA Sh47m17 09s mA Use Proper Motion at given time coordinate and wavelength Dec 51d03m59 55 PM RA larcsec year 0 005 Epoch 7000 00 PM Dec farcsec year 0 082 7 d Cancel p OK Background Estimates _ Seepa Estimates at 70 0 um Estimates m Position Type 13h29m52 375 47d11m4 Equatorial 2000 Fixed Single Pluto Barycenter 9 Moving Single My field ShS58mG0 005 60000m00 Equatorial 2000 Fixed Single Zodiacal Light My sr Interstellar Medium Mly sr Cosmic Infrared Background Miy sr Delete J Modify Show Visibility Show Background Total Background iMi sry Fi i New Target Done 5 Observations Tota Duration hrs 0 0 Her Target My_field Type Fixed Single NASA Herschel Science Center Target and Instrument settings PACS Photometer under the Observation menu 6 6 6 PACS Photometry f Unique AOR Label PPhoto GP_5F Ea Unique AOR Label Target Galactic_field_59 Type Fixed Single Position 19h45m00 00s5 4 24d18m00 0s5 Target information a er M f New Target d Modify Target y 2 Target List Y Number of visible stars for the target 25 stars in Star Tracker St
5. ance is set automatically e Square Map makes observation scheduling easier number of scan legs is set automatically e Cross scan distance lt 105 ensures overlapping between scan legs for all array to map angles in sky coordinates e Cross scan distance of 51 sub array size gives relatively flat exposure maps in Sky coordinates whatever the array to map angle NASA Herschel Science enter Scan Map AOT Settings User input parameters for Scan Maps e Filter e Scan Speed e Scan Leg Length Choice of Repetition Factor e Cross scan Distance e Number of Scan Legs e This sets the sensitivity of the observation once the e Square Map other parameters are set e Homogeneous Coverage Orientation Reference Frame If repetition factor gt 1 it is recommended to use an e Orientation Angle even number of scan legs to minimize satellite slew e Orientation Constraint overheads e Repetition Factor e Source Flux Estimates optional e The repetition factor also offers flexibility when combined with other parameters e g 1 repeat slow Cross scan distance Qg AOE in Scan leg length NASA Herschel Science Se Hal Scan Map AOT Settings User input parameters for Scan Maps e Filter e Scan Speed e Scan Leg Length e Cross scan Distance e Number of Scan Legs e Square Map e Homogeneous Coverage e Orientation Reference Frame e Orientation Angle e Orientation Constraint e Repetition Facto
6. ar tracker target Ra 116 25 degrees Dec 24 3 degrees ia better be gt 9 Instrument Settings 70 and 160 um Blue channel filter selection OR 100 and 160 um 5 Source flux estimates and gain settings 60 85 microns band yf EEE ICH a ee TERN Source Flux Estimates _ 85 130 microns band et Observing Mode Settings Repetition factor Source type and mapping mode settings Repetition 1 J Setthe Observing Modes ee een To control the absolute sensitivity consider adjusting the number of repetitions E f Observation Est Add Comments AOR Visibility page 7 p 8 P Cancel OK J NASA Herschel Science Center Target and Instrument settings PACS Photometer under the Observation menu A PACS Photometry Geman Unique AOR Label P lt Fe f Unique AOR Label PPhoto GP_5F Target Galactic_field_59 Type Fixed Single Position 19h45m00 00s 424d18m00 0s Target information New Target Modify Target Target List stars in Star Tracker Number of visible stars for the target 25 Star tracker target Ra 116 25 degrees Dec 24 3 degrees Instrument Settings Source flux estimates and gain settings Source Estimates 7O and 160 um Blue channel filter selection OR 60 85 microns band r _ Source Flux Estimates lt r ne 100 and 160 um 85 130 microns band u Saturation limits drive l the change of readout Sour
7. caltech edu sc index php Pacs InstrumentDetails a Ae Observing Mode Settings Choose one of the modes below Observing mode parameters Scan Map Medium Select the speed Scan leg lengths arcminutes No Homogeneous coverage Unique AOR Label PPhoto GP JSF ia f Cross scan step arcseconds 2 0 Square map Target i flactic_fiel d Positiog 19h45m0t Number of scan legs Map orientation 1 Fi New Target Modif ii Orientation angle reference frame Array Orientation angle degrees 45 0 Number f visible stars for Star tragker target Ra 116 Orientation constraint Angle from degrees 0 0 Angle to degrees 360 0 Instrume Blue channel filtr selection So 60 85 microms band a Cancel O 85 130 micr ns band Observing Mode Settings Repetition factor Source type and mW ping mode settings Beraten 1 Setthe Observing Modes To control the absolute sensitivity consider adjusting the number of repetitions if SSeS a AOR Visibility RE SS OE Observation Est Add Comments nhse NASA Herschel Science Center User input parameters for Scan Maps e Filter e Scan Speed e Scan Leg Length e Cross scan Distance e Number of Scan Legs Square Map Homogeneous Coverage Orientation Refer
8. ce Flux Estimates EEE j electronics gain Optional Enter source estimated data for S N calculation D Low gain setting AA reduces sensitivity Saturation limits are Warning Specifying a very bright source will induce a change in gain settings Please check applicable flux limits in the HSpot User s Guide Point source flux density mJy Extended source surface brightness MJy sr very conservative Band microns 60 85 Blue band 300 0 Blue band 270 0 Red band 40 0 130 210 Redband 100 0 il u Cancel Nicolas BILLOT NHSC June 2010 page 8 Number of Objects NASA Herschel Science Target and Instrument settings Gain Setting Filter Point source Jy Extended source GJy sr Blue 220 290 Green 510 350 Red 1125 300 e HSpot saturation limits are very conservative they assume the peak of the PSF sits on the brightest pixel e Low gain setting reduces the sensitivity higher digitization noise e We recommend to switch to low gain setting only if source flux significantly exceeds the official saturation limits e If source flux marginally above saturation limit put in a lower flux to fool HSpot and avoid switching to low gain setting 0 50 100 150 200 250 300 Signal mv Room left to accommodate the signal WARNING if you fool HSpot gain setting by putting in lower flux estimates then SNR estimates become irrelevant page 9 See PACS Key Information on NHSC website https nhscsci ipac
9. d backgrounds Limited area of homogeneous coverage page 23 Detailed comparison in AOT release note htto herschel esac esa int Docs AOTsReleaseStatus PACS PhotChopNod ReleaseNote 22Feb2010 pdf Point Source Observations Chop Nod mode eco User input parameters for Chop Nods e Filter e Dithering e Chopper avoidance angle e Repetition Factor e Source Flux Estimates optional 6000 Unique AOR Label PP Targ Pos Number Star trac Cancel Instrument Settings Blue channel filtr selection Source flux estimates and gain settings Nod 1 chop A q q p 60 85 micros band 85 130 micrgns band Nod 1 chop B Observing Mode Settings ARE EEPE Repetition factor Nod 2 chop B Source type and mawping mode settings Set the Observing Modes Repetition 1 To control the absolute sensitivity consider adjusting the number of repetitions nod1 chop A nod1 chop B nod2 chop A nod2 chop B nhse NASA Herschel Science enter Point Source Observations Chop Nod mode re op eet mach te RE He hth ae P EERS Mt i Tau pi Sm a et a fer i t b ni Ar ce FL Dither is recommended for faint sources e 3 position dither along Y axis of spacecraft using the chopper with 8 5 throw e Possible dither along Z axis by concatenating AORs with slightly shifted target positions Spacecraft dithering rather than chopper dithering e Check AOR overla
10. dither the entire map by shifting slightly the center of the map and concatenate pairs of scan X scan AORs scenarios that give same sensitivity in final map e 1 Scan at 20 s versus 3 Scans at 60 s AOR execution time is significantly higher in case of fast scan due to longer turnover times between scan legs It is prohibitive for small maps overheads gt gt overheads e 1 fine Scan short cross scan distance versus 3 loose Scans larger cross scan distance while covering the same area it requires to un tick homogeneous coverage AOR execution time is similar but fine scanning gives more homogeneous coverage page 22 nhse NASA Herschel Science Point Source Observations 2 Options Mini scan Map Chop Nod point source e Better characterization of target close vicinity Advantages for source fluxes in range 5OmJy 5OJy e Better characterization of larger scale structures Stability of reconstructed PSF RPE lt 0 3 e Larger area of homogeneous coverage e High spatial resolution e High redundancy as more pixels see the source e High photometric accuracy for isolated sources e Better sensitivity efficient high pass filtering e Actual sensitivity worse than HSpot numbers e No negative beams in the map e Rely on very few pixels e OK for targets with large positional uncertainty e Positive negative beams in final image e Relatively large overheads still more sensitive Limitations due to crowde
11. e a a ra Observation Est id Comments AOR Visibility i E 7 Cancel OK NASA Herschel Science Center PACS Time Estimator Message eco Messages PACS Photometer AOT ObsMode Large source line scan mode no chopping ScanLeg 1500 0 arcsec number of legs 10 leg separation 154 9 arcsec scan speed 20 00 arcsec sec PHOTO observed size 1 605 00 x 1 612 71 arcsec PHOTO observed area 2 588 395 arcsec Nod pattern as applicable No nodding S C 1s in line scan mode Dithering information Dithering information is not applicable Duration information AOT duration w overheads 1058 sec AGT duration comprises an sky plus setup and CAL during siew Breakdown of AOT duration On sky time w overheads 999 sec actual on sky time 750 sec Setup and CAL during slew w overheads 59 sec actual calibration time 31 sec AOT cost includes time to slew to source 999 180 1179 seel Sensitivity information Effective on sky time one spatial resolution element 6 7 sec Effective on sky time central resolution element 120 0 sec central area point source sensitivity red 6 25 mJy I Zul central area point source sensitivity blue 2 79 mJy map averaged point source sensitivity red 26 54 mJy extended surface brightness sensitivity 3 23 MJy sr map averaged point source sensitivity blue 11 85 mJy e
12. ence Frame Orientation Angle Orientation Constraint Repetition Factor Source Flux Estimates optional Cross scan distance Scan leg length NASA Herschel Science saeCenter scan Map AOT Settings User input parameters for Scan Maps Filter e Scan Speed e Scan Leg Length e Cross scan Distance Choice of Scan Speed e Number of Scan Legs e Square Map e Homogeneous Coverage e Orientation Reference Frame e Orientation Angle e Orientation Constraint e Repetition Factor e Source Flux Estimates optional e Medium or Standard 20 s for optimum modulation of the signal from the telescope motion in terms of 1 f noise e Fast 60 s for large maps at the expense of degraded PSFs 10 60 elongation in scan direction and longer overheads due to longer turnover Cross scan distance ti me C Scan leg length NASA Herschel Science enter Scan Map AOT Settings User input parameters for Scan Maps e Filter Scan Speed Choice of Map Size Parameters e Scan Leg Length e Cross scan Distance e Number of Scan Legs e Square Map e Homogeneous Coverage e Orientation Reference Frame e Orientation Angle e Orientation Constraint e Repetition Factor e Source Flux Estimates optional Cross scan distance C Scan leg length e Scan leg length sets dimension of one map side lt 20 e Use Homogeneous Coverage for large maps Cross scan dist
13. ntormation Duration PPhoto 0000 45deg GalPlane_I59 19h46m00 0 Fixed Single wm fe PACS Photome Scan map 1179 PPhoto 0000 135deg GalPlane_IS9 19h46m00 0 Fixed Single m PACS Photome Scan map 1058 Constraint Editor Constraint Editor Tool Add Constraint then Drag AORs to Constraint Window Group Follow On Add Constraints Parameters Add Sequencing Add Group Within Modify Parameters AddConcatenation Add AOR Timing Add Comments Perform Action Remove Get AOR Move Up Move Down Drop AORs Constraints Y 1 2 B Concatenation 0000 Total Duration 00 37 17 PPhoto 0000 45deg PPhoto 0000 135deg Observations GalPlane_159 POSS2 UKSTU Red Target GalPlane_IS9 Type Fixed Single Total Duration hrs 0 6 page 19 NASA Herschel Science enter Scheduling Constraints Timi ng co nstraint 600s overheads instead of 180s AOR executed within specified time period ABSOLUTE TIME BEFORE or AFTER e g period when moving target is out of Galactic Plane Grouping Follow on constraint e Sequence 600s overheads instead of 180s sequence of AORs executed in specified order within a given period of time e Chain or Concatenation Spare Observatory slew time 180s CalBlock duration AORs are executed in the order specified with NO interruption in the chain e g scan and X scans or PACS 3 band observations e Group within 600
14. pdate feature under the Options menu on the HSpot toolbar er Need version 5 0 x for current AO NASA Herschel Science enter Planning an Observation with HSpot 1 Provide Target Information 2 select the Instrument Settings band gain 3 select the Observing Mode and Setup Observational Parameters to Suit your Scientific Goal 4 Check AOR with Visualization Tools Check Sensitivity Estimates 5 Concatenate Chain AORs Together to Build your Observation For comparison or inspiration Vie You can view accepted observing proposals AORs View Accepted Proposals under the File menu ne Cancel You will need the exact proposal name e g KPGT_aabergel_1 page 4 that you can find at http herschel esac esa int Key_Programmes shtml Q Two Science Cases to illustrate 2 AOTS Only two observing modes survived the Performance Verification Phase Small Source AOT and Raster Map AOT decommissioned Scan Map and Chop Nod Scan Map of a Galactic Point Source Observation Star Forming Region Mini Scan Map and Chop Nod page 5 nhise ANASA Herschel Science Hate Define a Target or Target List New Target Target List Herschel Observation Planning Tool Launch version LED gt ER e Fixed or Moving Targets e Resolve the Name Label Scania aian O00 Target Target
15. r e Source Flux Estimates optional Cross scan distance f f j Scan leg length Choice of Map Orientation Parameters e No magic angle like SPIRE focal plane filled with bare pixels e Absolute flexibility all scan directions are possible in array or sky reference frame with optional constraints e BUT think twice before putting a constraint to your observation Orientation constraints translates into scheduling constraints hence in observing time penalties e Avoid scanning at array angles of O and 90 because of empty inter module gaps e f scan maps in Sky coordinates without array constraints the map coverage depends on the exact observation date and there is a risk that the array to map angle is 0 or 90 Check the AOR overlay on image at given visibility windows 3 NASA Herschel Science enter Scan Map AOT Settings a array to map angle B map orientation angle Orientation Angle Reference Frame Options RE poston ange Observing Modes LD oe epee nt Scan Map x Select the speed Medium WAR N NG n Scan leg lengths arcminutes 01 M N UTES PENALTY FOR CONSTRAI E1 Homogeneous coverage No j T Cross scan step larcseconds 2 0 Array with sky constraint T Square map Number of scan legs Map orientatisa Orientation angle reference frame Array Orientation angle Tdeoreers rientation constraint
16. s overheads instead of 180s AORs executed within a given period of time but in any order e Follow On 600s overheads instead of 180s AORs observed in sequence at given intervals of time appropriate for observation of variable targets e g YSOVAR like programs page 20 NASA Herschel Science enter Science driven Parameter Choices for a Scan Map of a Star forming Region Safe choices for observing a star forming region e 20 s or 60 s or SPIRE PACS Parallel mode if PSF quality not critical e Homogeneous coverage e Square map e Instrument reference frame is ARRAY with array to map angle of 45 e Concatenate X scan with orientation angle of 135 spare 2 minutes slew time Map making algorithms require the highest pixel and scan direction redundancies possible so that scan and X scan observations are highly recommended to preserve the extended emission i e separate 1 f noise from large scale structures in the data processing e Possibly Concatenate pairs of scan X scan AORs to observe in 3 bands i e observing at 70 160 um AND right after at 100 160 um spare another 2 minutes slew time page 21 ANASA Herschel Science Se Hal Science driven Parameter Choices Other Tips and Tricks For deep scan maps and best PSF reconstruction e Instead of multiple repeats at the same location one should e decrease the cross scan distance between legs to increase spatial redundancy within a single map e
17. xtended surface brightness sensitivity 11 82 MJy sr ancel nik j k d i ave messages C page 17 Map geometrical parameters summary Total AOR duration Average pixel exposure time The final sensitivity of your observation depends to some extend on the data reduction e g highpass filtering MADMap source registering to correct for pointing errors etc nhse NASA Herschel Science Check your observation Always visualize your observations and check the coverage maps Herschel Observation Planning Tool Launch versior tan Mouse Control i Shift Left Button Centre the Image at point j Mouse Any gt lt G3 GalPlane_IS9 POSS2 UKSTU Red ervations GalPlane_Is9 POSS2 UKSTU Red Target GalPlane_l59 Type Fixed Single Total Duration hrs 0 0 page 18 Check map orientation in chosen visibility window P Check coverage homogeneity exposure time per pixel in seconds IF scan map in sky coordinates check that the array to map angle is not 0 or 90 nhse NASA Herschel Science Center scheduling Constraints Group Follow on Constraints under the Tools menu Herschel Observation Planning Tool Launch version Do MS Mouse Control e Shuft Left Button Centre the Image at point Mouse Any 3 4 8 Observations Astronomical Observation Requests AORs Label Target Position Type T G yif Instrument Mode I
18. ys and coverage maps Chopper avoidance angle e Penalty of 600 seconds for scheduling constraint Pixel size arcsec xel size e Constraint not fed back in HSpot visibility window Nyquist E 0 514 0 100 150 200 Wavelength um Repetition factor Number of AB nod cycles to reach required sensitivity page 25 NASA Herschel Science enter Point Source Observations Mini Scan Map Same Template as the large scan map example presented previously Recommended parameters that make mini scan maps the least inefficient possible in terms of overheads and idle times e 20 s scan speed e Scan along the diagonal of the array i e at 70 and or 110 in array coordinates e Concatenate X scan map at 110 or 70 Allows various kinds of mapmaking techniques and provide higher quality photometry and better Spatial characterization of the near source vicinity e NO homogeneous coverage and NO square map e 10 scan legs with cross scan distance of 4 For shallow observations less legs but even number to minimize satellite movement with larger cross scan distances or skip cross scan direction e Scan leg length from 2 to 4 3 length optimal usage of constant scan speed of 20 s but during idle positions the source is outside the array 2 length Source is always on array but acceleration deceleration of source on array might require more elaborated processing e Repetition factor as needed to reach the
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