LSO-MIN-ESO-60400-00..
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1. than without In practice one is likely to get a combination of both effects With a single set of ADCs the use of plane ADCs and refocusing the telescope to bring the object in focus on the fiber will cause a defocused sky on the sky fiber As long as there is really only sky on this fiber this will have no effect on sky subtraction accuracy and one set of ADCs will be fully adequate Apart from the photometric light loss in the ADC there are no consequences for flux calibration and also the spectrograph PSF is not affected The alternative mentioned by Alain to install a second set of ADC prisms in the free ADC position is especially useful if you want to perform nod and shuffle and use both Page 7 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 fibers as object fibers in an alternating fashion Even if this is not being planned now it seems a good idea to order two or even three sets also in view of the low cost of the ADCs JPT Based on the previous experience poor efficiency caused by we believe focal ratio degradation in the fibres it seems clear to me that we should avoid at ALL costs changing the F ratio of the input beam therefore the clear choice to me is the plane parallel prisms option with prisms installed in BOTH OBJ and SKY beams so as to permit both the possibility to observe with either aperture AND the field of view being in focus over the maximum area of the TCCD which i2. caused by the prism optics Resolution of this item will be made following the procedure below It was also noted that the curved surface will cause a change in the focal ratio of the beam exiting the ADC and hence arriving at the fibrehead This phenomenon should be documented in the Optical design document along with an impact study describing the resulting effect on the optical system 1 AGi and HDe will together derive the ADC Fibrehead distance tolerance upon which they both agree 2 Meanwhile JAI will verify if achieving the currently defined tolerance or the new tolerance derived by AGi and HDe should it be less than the currently defined one is practical from the mechanical perspective 3 Meanwhile JPr will verify if the curved surface for focus correction is actually justified The issue is after applying the necessary M2 focus offset to correct for the de focus caused by flat prisms will the image quality in the TCCD field be suitable for guiding on field stars If there is no signifcant mechanical problem to achieve the currently defined tolerance or the new tolerance derived should it be less than the currently defined one then the action item is resolved Otherwise if the M2 focus change is acceptable then the optical design can be changed to remove the curved surface If neither of these two possible solutions can be reached a redesign and further Design Review s will be required 4 2 Sign off Dear John Here
3. concerned that SciOps would want to operate outside this range His concern was acknowledged but it is unwarranted since FEROS has a fixed instrument configuration and is only ever operated within the above range Moreover the AR Super Triolin coating is used in other components of FEROS so even if the ADC used some other Page 9 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 broader range coating it would be pointless since FEROS is already constrained by the other components which do use the AR Super Triolin coating 11 Science Fibres A basic description of the FEROS Science fibres was provided for HDe in order to familiarize him better with the FEROS instrument Also discussed was the relative efficiency of the Science Fibres and the fact that it may be necessary to change the definition of OBJECT and SKY fibres at a future date e g if a new fibrehead is installed according to which fibre has the best ACTUAL efficiency 111 Prism size clarified 12 5mmx2x3mm iv Number of prisms to be purchased clarified 4 v Total transmission losses due to ADC optics clarified less than 8 across the entire 350 950nm range vi Requested Manufacturers Quality Assurance clarified measured transmission curves and waveform deformations will be required from the manufacturer Review of questions regarding the documentation raised by HDe prior to the FDR Below each point is addressed accord
4. lens of WFI The ideal is that each pixel in WFI can see only the rear side of a baffle for this one may have to place more baffle rings Reply It is planned in a slightly different way baffles black velvet have been already used to decrease the stray light on the FEROS adapter with good success All mechanical parts close to the beam will need the same Pinhole test will be done to check By A Gilliotte HDE 008 Document ADC optical design document 60400 0003 Page 10 Comment the use of ADC for ZD lt 30 deg will be recommended I thought it is permanently in the beam Reply No it must be removable since it clashes with one of the other components of the adapter the Sliding Calibration Selection Mirror By J D Pritchard Page 14 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 HDE 009 Document ADC optical design document 60400 0003 Page 15 Comment Super Triolin is a good choice but one should realize that the slopes outside the passbands are very steep Anyway the same coating is used in FEROS so this should be no problem Reply Choice made according to the recommendations of HDe By A Gilliotte HDE 010 Document ADC optical design document 60400 0003 Page 16 Comment Please explain the philosophy behind the requirements on prism rotation 2 deg and tilt prism angle 1 deg Do you mean that tolerances are or total range Reply Th
5. plan By J D Pritchard HDE 002 Document User requirements 22400 0002 issue 1 1 Page 5 10 Comment Why do lamps have to be pre warmed How long This is not done on UVES Here the lamp is just switched on first then slides are moved in detectors wiped etc For repeated exposures it is better to leave the lamp on at the end of the first exposure to avoid need for warm up again and only to switch of at the end of the series Reply We have been pre warming the lamps since I became FEROS instrument scientist I had no good reason it just seemed like a good idea to me commonsense if you like However it turns out that it is well known that minute variations in fibre position temperature light injection geometry and wavelength cause Modal noise in fibre fed high resolution spectrographs see Baudrand amp Walker 2001 PASP 113 851 One regular FEROS observer H Hensberge whom you probably know well has detected what appear to be variations in blaze profile from flatfield to flatfield obtained just minutes apart which we are currently thinking maybe due to modal noise Certainly warming up the lamps might be helping to minimize this effect In the daily Standard Calibrations obtained during daytime when we have plenty of time we warm up the lamps for Smins before using them and indeed leave them on while we acquire multiple exposures with the same lamp Both a warmup delay and leaving the lamps on are handled with in
6. the observing sequence files Unfortunately due to the configuration of the FEROS Calibration Unit it is not possible to keep the lamps on while different lamps are being used since the lamps would contaminate each other Page 11 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 There is also a small amount of light leak in SCIENCE exposures when the calibration lamps are left on during science exposures so we do not recommend to do so Moreover we do not have a budget to supply enough lamps for continuous usage the way for example it is done with HARPS JPr also agreed to provide HDe results of investigations into lamp stability vs warmup time should such an investigation eventually be made By J D Pritchard HDE 003 Document User requirements 22400 0002 issue 1 1 Page 7 warning system Comment A beeper on the instrument is not sufficient and anyway the standard Pulpo beeper is very weak One must have a way of calling the engineer who is on duty and normally not in the dome Alarming him should not rely on SW This can be used for monitoring but not for alarms Reply GAn clarified that at LSO unlike PO the warning system is indeed already implemented via the observatory PAGER system and apologized for any confusion caused by the use of the word beeper instead of pager in the User Requirements By G Andreoni HDE 004 Document User requirements 22400 0002 i
7. 04 RES ADC Prism Drive Error Analysis J Alonso July 8 2004 RE6 Degradation of ADC correction due to positioning errors of the prisms I Saviane July 19 2004 gt 1 3 APPLICABLE DOCUMENTS AP1 FEROS ADC Optical Design Doc No 2p2 DSD ESO 60400 0003 Issue 1 0 and 1 1 A Gilliotte July 16 2004 AP2 FEROS ADC Control Electronics Doc No 2p2 DSD ESO 60400 0001 Issue 1 0 J Alonso April 18 2004 AP3 FEROS ADC Mechanical Design Doc No 2p2 TRE ESO 70400 0001 Issue 1 0 W Eckert May 5 2004 1 4 ACRONYMS amp ABBREVIATIONS ADC Atmospheric Dispersi n Corrector AVI Assembly Verification Integration FEROS Fibre fed Extended Range Optical Spectrograph FDR Final Design Review Page 5 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 2 FDR RESULTS The Verdict of the external reviewer Hans Dekker was that the project is On hold pending the outcome of action items related to Prism rotational positioning tolerance Prism Fibre head distance tolerance Documentation of AVI Commissioning procedure Corrections and additions to Optical Drawings F ratio change calculation and impact study le Galo Of these five action items only 1 is felt to be a potential serious show stopper but one is enough Therefore the project is on hold pending the successful resolution of the above items Should one or several items not be successfully re
8. EUROPEAN SOUTHERN OBSERVATORY Organisation Europ enne pour des Recherches Astronomiques dans l H misphere Austral Europ ische Organisation fiir astronomische Forschung in der s dlichen Hemisph re LA SILLA OBSERVATORY FEROS ADC FINAL DESIGN REVIEW Doc No LSO MIN ESO 60400 0001 Issue 1 0 Date 12 October 2004 Prepared J Alonso Name Date Signature Approved H Dekker Name Date Signature Released J Melnick Name Date Signature Page 2 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 CHANGE RECORD Section Paragraph 12 10 2004 Page 3 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 INDEX OF CONTENTS LL INTRODUCTION ssscscicssissssicccdcscssecsssssecsdcvsovecsestecesdevsscesvasscossccvesdeoasescusdeceedecsasesesbdcesetecsossesssaeeseees 4 Lk GPURPOSE AND SCOPE ees A 1 2 RERERENCERDOCUMENTS ccccccesessssseeseeesseeseeeeseeeseseeesueesesususesususueuaueususuaeenenees 4 L APPLICABLE DOCUMENT S va 00 4 1 4 ACRONYMS amp ABBREVIATIONS ccoccccccncnoncncncnonononononononononononononononononononononononononononononononononos 4 2 AAA isee ec irose okinarate riase oS eseria oina sorsa sa roin iE 5 Si ACTION ETEMS E T E E EE E EE E E EEEO R 5 3 1 PRISM ROTATIONAL POSITIONING TOLERANCE cccccccccccncononononononononononononononononononononononononenoninenonoso 5 3 2 PRISM FIBREHEAD DIS
9. TANCERTOLERANCE 6 3 3 DOCUMENTATION OF AVI COMMISSIONING DROCEDURE 6 3 4 CORRECTIONS AND ADDITIONS TO OPTICAL DRAWINOGS 6 3 5 F RATIO CHANGE CALCULATIONS AND IMPACT STUDY cocccccccncncnnononononononononononononononononononononenenenes 6 3 6 DOCUMENTATION OF SWC ADC IMPLEMENTATION ccccccccccccccccecececescscsesescsescecsesesessesseseeseeees 7 Ae APPENDEX E OE E E E NN 8 A MINUTES tao si lodo IES EE 8 Aid o gt AIN e ei ias 17 Page 4 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 1 INTRODUCTION 1 1 PURPOSE AND SCOPE This document is intended to serve as a formal statement for the FEROS ADC FDR held at La Silla Observatory on 6 July 2004 References to the design documents presented for review as well as the outcome of the meeting in the form of the minutes and actions required for approval are herein included together with the final verdict of our external reviewer 1 2 REFERENCE DOCUMENTS RE1 FEROS II User Requirements Doc No LSO URS ESO 22400 0002 Issue 1 1 J Pritchard September 8 2003 RE2 Implementation of ADC for FEROS User Requirements Doc No LSO URS ESO 90400 0002 Ivo Saviane April 11 2003 RE3 FEROS ADC CONCEPTUAL DESIGN Doc No 2p2 DSD ESO 60400 0002 Issue 1 J Alonso W Eckert A Gilliotte February 28 2004 RE4 FEROS II Operation Plan Doc No 2p2 PLA ESO 90100 0001 Issue 1 1 J Pritchard June 22 20
10. e object in focus on the fiber will cause a defocused sky on the sky fiber As long as there is really only sky on this fiber this will have no effect on sky subtraction accuracy and one set of ADCs will be fully adequate Apart from the photometric light loss in the ADC there are no consequences for flux calibration and also the spectrograph PSF is not affected The alternative mentioned by Alain to install a second set of ADC prisms in the free ADC position is especially useful if you want to perform nod and shuffle and use both fibers as object fibers in an alternating fashion Even if this is not being planned now it seems a good idea to order two or even three sets also in view of the low cost of the ADCs Best regards Hans September 3 2004
11. e two deg is in rotation on both prisms to adjust correction according ZD expecting a prism relative angle error of 4 deg The 1deg is the tolerance for mechanics to ensure the prism mounting with respect the beam These are tolerances NOT total ranges By A Gilliotte HDE 011 Document ADC optical design document 60400 0003 Page 16 manufacture Comment I would have expected prism manufacturing drawings What are the tolerances on surface flatness radius prism angles clear apertures etc Reply Drawings created and supplied via email to be added to design document Also an error in the prism diameter was detected 12 0mm but should be 12 5mm and it was pointed out that tolerances on the prism angles should be included in the drawings By A Gilliotte Page 15 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 HDE 012 Document ADC optical design document 60400 0003 Page Acceptance tests of prisms Comment The document does not explain the acceptance criteria and tests that will be done on the prisms by Fichou or at La Silla before AIV of the complete unit How do you know that you got what you ordered What is the design wavelength undeviated wavelength of the prisms Do you intend to measure it what will be the effect if this is not the design wavelength Reply We will do a check here with collimated light and UG1 filter measuring the distance between both corres
12. er the zero backlash gears due to space constraints It was agreed that the resolution of this problem would be handled by an action item which would follow the following procedure 1 ISa will verify the required prism rotation accuracy The current user requirement specifies an accuracy of 1 degree which constrains light losses to less than 5 He will check on light losses for an accuracy of 2degrees 2 Depending on the outcome of ISa s study JPr will decide on the final user requirement for the prism rotation accuracy 3 Meanwhile JA will make a complete prism rotation accuracy error budget analysis for the currently proposed solution If the error budget derived by JAI is within the final user requirement no further action will be required If not the MEC design will need to be reconsidered probably it will be necessary to find a way to implement the zero backlash gears Page 17 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 Tf neither of these two possible solutions can be reached a redesign and further Design Review s will be required HDe raised concerns over the tolerance of the ADC to Fibrehead distance The optical design document 2p2 DSD ESO 60400 0003 states a tolerance of 0 2mm HDe feels this to be unnecessarily restrictive AGi states that the tight tolerance is due to small radius of curvature of the prism surface used to correct for the de focusing
13. iguration keywords Juan Carlos Guzman Tanaka September 8 2004 Page 8 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 4 APPENDIX 4 1 MINUTES FEROS ADC Final Design Review Date 2004 July 6 08 30AM CLT Held at La Silla video conference link with Garching and Vitacura Minutes Presence La Silla J Alonso Eng G Andreoni Eng A Gilliotte Opt J C Guzman SWC J Pritchard Project Scientist Garching H Dekker External Reviewer Vitacura I Saviane SciOps Apologies W Eckert Mec sick Notes on Proceedings Author J D Pritchard Question from HDe Who is reviewing who Clarification it was agreed that the purpose of this review was to primarily review the opto mechanical implementation for which HDe was himself the primary responsible since the science issues had already been addressed during the Conceptual Design Review external reviewer L Pasquini Presentation by AGi ADC optical design The principal features of the optical design were described by AGi He also discussed the implications of the physical limitations caused by the available space in which to install the ADC During the presentation the following issues were clarified i AR Super Triolin coating HDe reminded that the AR Super Triolin coating is superior to the previously proposed MgF2 coating over the range 350 950nm but significantly worse outside this range He was
14. ing to the responses made prior to the FDR by various parties via email and according to the discussions during the review Note HDE 001 to HDE 003 has no relation with the ADC but since these issues are part of the FEROS User Requirements document our external reviewer kindly commented on them HDE 001 Document User requirements 22400 0002 issue 1 1 My understanding is that we re only reviewing the ADC Still I have some other comments for what they re worth p 5 6 and 10 Stabilized LED Comment On UVES and Giraffe we use a 10 W current feedback halogen lamp with a 20 nm filter centered at 450 nm After a 10 min warm up it is stable to 1 which is OK for testing detector gain and linearity Since one of the main purposes is to detect contamination one must work in the blue and with a suitably placed flat field screen Desired illumination homogeneity is 10 or better all over the chip A point source is less well suited to check for contamination Why do you need 3 different colors wavelengths Reply The LED system along with most of the rest of the FEROS II project is already implemented and is working well You can see the results of CCD tests with all three sets of LEDs plus BetaLight system for comparison at http www 1s eso org lasilla sciops 2p2 E2p2M FEROS CCDYTests index html Page 10 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 In particular see the resu
15. is my sign off on the Action Items 1 Prism rotational positioning tolerance 11 Prism Fibrehead distance tolerance 111 Documentation of AVI Commissioning procedure iv Corrections and additions to Optical Drawings v F ratio change calculation and impact study Issue i is not in my scope but I believe that is has been satisfactorily resolved The updated optical design report by Alain clarifies the issues ii to iv in a good way On issue v which is related to the way the defocus introduced by ADC is compensated the report lists the consequences of either choice and an alternative but makes no recommendation see p 16 Page 18 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 My view is as follows I consider the F ratio due to a curved surface on the ADC change important since the faster F 7 6 beam will be at least partially vignetted in the spectrograph The amount of vignetting depends on the extent to which the spectrograph accepts a faster beam than the nominal one Changing the F no will thus affect flux calibration If the spectrograph fully accepts the faster beam there will be no vignetting but there may be an issue of changing spectrograph PSF because the beam on the detector with ADC in is faster than without In practice one is likely to get a combination of both effects With a single set of ADCs the use of plane ADCs and refocusing the telescope to bring th
16. ll be integrated on the support arm on the lab The prism angle position dispersion axes is required to manufacturer to be marked on each unit The orientation mark will be used for mounting Simulation on lab will allow the dispersion axes check for different ZD values the same collimated light test bench mentioned above could be also used with one and two mounted prisms The mounting of the ADC support arm on the adapter will be done at the theoretical back focal lens position for the prism An F 8 beam using a sighting telescope will be aligned on M3 center and fiber spot to simulate the telescope beam the prism rotation wobbling effect has to be check for zenith prism angle no correction rotating both prisms on the same direction with the same offset The Harps setting will be used with the calculated prism position The M3 field inversion on the reflection plane will reverse N S dispersion effects By A Gilliotte It was agreed that the AVI commissioning procedure must be included in the Optical design document An action item will be created to follow up on this Page 16 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 HDE 014 Re Commissioning of ADC Comment You may want to temporarily install a filter like UG1 in the viewer This has two passbands at 350 nm and 750nm In good seeing this will produce a double or elongated image if the ADC is not working correctly An alternati
17. lts for the Red LEDs for the 225kHz 1 low readout mode which we have been taking on an almost daily basis for several months now The stability during a 1hr period and the illumination homogeneity are not known at this moment but I will endeavour to measure them during my current tourno and possibly before the ADC FDR Each colour of ADC is in fact a set of three mounted on a ring installed in front of the FEROS camera The plastic covers have been roughened to diffuse the light so we hope that this is better than a point source We decided to implement the three different colours of LED as a test case basis Since this is a relatively new technique which we may consider implementing for other instruments we decided to try to test it over a broad range of configurations The mounting ring does not produce any vignetting to the beam and so can be left installed permanently The LEDs are remotely controlled Thus there is no longer any need to enter the FEROS Climate Control Room to install and remove the BetaLight system previously used for CCDTests though we can do so and will continue making BetaLight tests on a long term basis as a means of long term comparison HDe reiterated the benefits of using the CCDTest flats to monitor for contamination and to use the bluest available light source since blue light is more sensitive to contamination than red JPr agreed to take both points into consideration for an update of the FEROS Commissioning
18. onment conditions is already built into the standard VLTSW ADC implementation It can be turned off by setting the relevant parameters to zero which indeed is what is done for HARPS By J C Guzman SWC must provide documentation describing all parameters of the SWC ADC implementation so that SciOps can provide the relevant information for the definition of such parameters This information should be provided well in advance at least one month of the final implementation of the system By J Pritchard Page 13 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 SWC is in the process of documenting this information for HARPS The exact same information will be applicable to FEROS so that HARPS documentation can be consulted in due course By J C Guzman The relevant FEROS documentation will also need to be updated appropriately in due course By J Pritchard HDE 007 Document ADC optical design document 60400 0003 Page 9 10 Comment My concern is stray light in WFI due to out of field objects being able to illuminate metallic surfaces of the fiber system or other surfaces in the adapter If this is not already planned I recommend to paint all surfaces with optical black paint black anodization is NOT sufficient except those that must remain unpainted e g spindles or drive belt Place concentric baffles where possible at least at the entrance of the adapter and before the 1st
19. ponding images according design using a lens of focal 100 or 300 Both prisms in opposite angle positions will give blue red images on axis Between ZD 0 and 60 deg and the ADC correction with counter rotating prism the image moves within the parallactical angle by 2 5 arcsec meanwhile a ZD fixed to zenith and parallactic angle rotation the image doesn t moves But with a differential guiding as used on ADC the image displacement should be compensated by the guiding With the rotation I could not answer about undeviated wavelength it is changing by prism rotation The phenomenon of image wobble was also discussed Imperfections in the manufacturing meaning the prism angle is not precise and or imperfections in the glasses themselves will mean that the stellar image will in general be offset from the expected on axis position A tolerance on the decentering caused by this effect should be established And of course this effect must be characterized and verified to be within the defined tolerance during AVI commissioning By A Gilliotte HDE 013 Re AIV procedures for ADC Comment A description of the AIV procedure is missing both for the prisms but also for the complete facility Before you order the prisms you should know how you will perform the following tests Image quality and focus location Image wobble when rotating prisms Direction and alignment of prisms dispersion axes relation with encoder values Reply ADC prism wi
20. s of course important for guiding on a field star therefore As FEROS Instrument Scientist and Project Scientist for this ADC project my recommendation based on the information and opinion provided by Hans and our previous experience is that we adopt the plane parallel prisms solution I believe Alain should now prepare the final version of the Optical Design document where the adopted solution is stated rather than presenting the two possible options I also think it would be useful to retain the curved surface information in the document in a rejected option section or appendix for example 3 6 Documentation of SWC ADC Implementation In the following document is the information about the available parameters for ADC in the FEROS INS Sw It corresponds to the Base ICS User Manual pages 86 87 ftp ftp eso org pub vlt vlt pub releases APR2004 vol 5c VLT MAN ESO 17240 0934 pdf To check the parameters used in HARPS cmmCopy the hamcfg module and check the INS ADC keywords in hamcfgINS cfg Besides the configuration keywords there are other parameters related with the location of the instrument latitude and longitude which have to be updated for the 2 2m Those parameters are located in module fei file dbl feiEnv1 db Both values are in radians NOTE for SOF In fei module file dbl feiEnv1 db the table values for both ADC is not necessary anymore I think with APR2004 the max and min speed can be entered via conf
21. solved further design review s will be required A review board consisting of Hans Dekker and John Pritchard will review the action items and decide on the successful resolution or otherwise The deadline for completion of the review 1s August ue to vacations of people involved f the review is August 12 d i f people involved Additional action items not affecting the final verdict but required to be completed in due course 6 Documentation of SWC ADC implementation For details on the FDR meeting please refer to 4 1 MINUTES For the original sign off e mail from the reviewer please refer to 4 2 Sign off 3 ACTION ITEMS 3 1 Prism rotational positioning tolerance HDE This issue is not in my scope but I believe that it has been satisfactorily resolved JPT Ivo has clearly demonstrated that the prism angle positioning tolerance can be relaxed to as much as 3 degrees per prism without compromising the target efficiency Please refer to RE6 for details Page 6 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 JPT Jaime has measured the backlash for the belts and when combined with the stated backlash errors of the gears he arrives at a total foreseeable positional backlash error of 1 25 degrees per prism Well within the tolerance Please refer to RES for details JPT Under the agreement of the FDR that this item was the only potential show stopper and given the abo
22. ssue 1 1 Page 11 Comment The maximum image decentering of 0 2 arcsec seems a very tight requirement that should be reconsidered if it compromises the optical or mechanical design Replies We discussed this issue in the CDR and agreed to relax the constraint to the limit actually achievable by the proposed opto mechanical design By J Pritchard This looks like turning things around I suppose that the main driver is scientific output not the design If you have reasons to relax the constraints I d welcome them very much However it seems to me that there is no point in having something that is technically easier but does not improve the instrument The 0 2 arcsec comes from some calculations I did and confirmed by Donnelly et al actually 0 25 is the latest limit This is to have a flux loss of less than 5 but of course if we want to tolerate a larger loss then the limit becomes less stringent You were not in the recipients of an earlier email where I explained this so I ll send it to you soon afterwards BTW I repeated the computations for a 0 5 FWHM seeing see the attached graph which is the same as the previous one but replacing the 1 0 FWHM panel with the 0 5 FWHM Page 12 FEROS ADC FINAL DESIGN REVIEW 12 10 2004 Minutes Document Doc LSO MIN ESO 60400 0001 This can be used to compare with Alain s simulation For such a small seeing you need to displace the image by as much as 0 6 to see a flu
23. ve is to compare image location in U and R filters but I do not know if the slit viewer has a filter wheel and in that case the filters should be highly accurate no wedge Using filters will be a more sensitive method than merely measuring the wavelength dependent flux at the fiber output although of course this is the ultimate test Filters will also be helpful to debug the SW to drive the ADC Reply The UG solution will be appropriate since we do not have a filter wheel The Fibre head viewing technical CCD can be used to test alignment once installed in the telescope By J D Pritchard Beam footprint at ADC HDe asked what will be the beam footprint at the prism AGi responded that the beam size at the first prism surface in terms of the light path from the telescope i e the entrance surface will be 6 9mm while at the exit surface it will be 6 0mm Prism rotation JPr commented that on page 4 of the mechanical design document 2p2 TRE ESO 70400 0001 it is stated that The prisms can rotate endlessly but only in one direction This is incompatible with the requirements of operation since as ZD decreases the prisms must be rotated in one direction and as ZD increase they must be rotated in the other It was explained by JAl that this property results from the desire to avoid backlash which is expected to be of the order of 1 degree for the non zero backlash gears used in the current mechanical design which were chosen ov
24. ve results which clearly show that this is NOT a show stopper I recommend that the result of the FDR can immediately be upgraded to PASSED with Actions 3 2 Prism Fibrehead distance tolerance HDE The updated optical design report by Alain clarifies the issue in a good way Please refer to AP1 Issue 1 1 3 3 Documentation of AVI Commissioning Procedure HDE The updated optical design report by Alain clarifies the issue in a good way Please refer to AP1 Issue 1 1 3 4 Corrections and additions to Optical Drawings HDE The updated optical design report by Alain clarifies the issue in a good way Please refer to AP1 Issue 1 1 3 5 F Ratio change calculations and impact study HDE On this issue which is related to the way the defocus introduced by ADC is compensated the report lists the consequences of either choice and an alternative but makes no recommendation see AP1 Issue 1 1 p 16 My view is as follows I consider the F ratio due to a curved surface on the ADC change important since the faster F 7 6 beam will be at least partially vignetted in the spectrograph The amount of vignetting depends on the extent to which the spectrograph accepts a faster beam than the nominal one Changing the F no will thus affect flux calibration If the spectrograph fully accepts the faster beam there will be no vignetting but there may be an issue of changing spectrograph PSF because the beam on the detector with ADC in is faster
25. x loss of 5 By I Saviane HDe if the requirement does not compromise the mechanical and optical design it is fine however I am not happy with this requirement HDE 005 Document User requirements 22400 0002 issue 1 1 Page 11 point 5 Comment Why do you need a mode preset to mean parallactic angle Who would ever use it Reply Uhmmmm don t know at the time we wrote the ADC requirements we simply tried to cover all possibilities We have since agreed private communication between Juan Carlos Guzman and myself that we will accept the standard VLT ADC implementation which I understand to be continuous i e with an update period of about 10sec positioning By J D Pritchard HDE 006 Document User requirements 22400 0002 issue 1 1 Page 15 16 Comment dispersion depends on P T and RH Will you use meteo monitor data to drive the ADC If not what will be the error you make by assuming standard conditions Is this error larger or smaller than the 0 2 arcsec that is your spec Reply See http www ls eso org lasilla sciops feros Projects ADC index html where I did computations for a large range of parameters For conditions typical of La Silla relative humidity between 0 and 100 temperature between 0 C and 20 C and pressure between 765 and 775 hPa the relative effects on the atm diff refraction are smaller than 0 2 By I Saviane The possibility to set the ADC according to actual envir
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