1. Initial Alignment Check / Calibration in Vacuum Dennis Ebbets With substantial contributions from Tom Delker, Erik Wilkinson, Steve Osterman, Ken Brownsberger, Rich Brewster, Brian McLaughlin May 02, 2003 Updated after selection of NUV setup positions Previous versions: Apr 04, Feb. 27, 2003 Dec 04, Nov 26, Nov. 22, Oct 30, Sep 20, 2002

2. 2 This package contains Description of contents and sequence of tests for initial calibration in vacuum phase. These descriptions are inputs for the development of Real-Time (RT) commanding or Science Mission Specification (SMS) Plan for operational implementation is indicated in blue text for each test. Estimates of time requirements are included. These are meant to be total times, exposure + instrument overheads. Exposure times will be shorter than the times that appear in these tables. Test details developed in ‘Initial Alignment Check & Calibration in Vacuum.xls’ Descriptions of the calibration tests are transferred from this development document to Appendix A of the COS Thermal Vacuum Test Procedure

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4. 4 Activities in air prior to pump-down Install COS and RASCAL in Rambo RASCAL to COS alignment using metrology CDS relay optics to RASCAL entrance aperture alignment Verify CDS and RASCAL operability before pump-down COS turn-on and ambient Functional Test Test #40TA1 aperture scan (Verifies alignment of RASCAL to COS with light) –RT commanding based on prior alignment phase activities Pump-down

5. 5 CDS relay optics to RASCAL alignment One mirror in CDS relay optics is motorized and can be operated remotely to steer the beam onto the RASCAL entrance aperture. Coarse Alignment –Goal is to cover RASCAL input aperture with CDS light spot –Use Pt-Ne lamp on CDS lamp-only channel Use CDS ND filter and lamp current to adjust brightness –Inspect alignment by eye if possible –Use CDS video camera if necessary Fine Alignment –Use RASCAL reference detector to peakup alignment –Adjust for ~1000 cts/sec with nominal point-source aperture –Verify operability and use of RASCAL reference detector –Verify each RASCAL input aperture for common alignment to CDS Relay Optics –Verify expected throughput of each aperture

6. 6 Verify CDS and RASCAL operability before pump-down Exercise CDS Pt-Ne lamp with monochromator. Verify presence and count rates for emission lines 2200Å <  < 3200Å using RASCAL detector. Won’t see shorter wavelengths in air. Adjust monochromator input and output slit widths to give at least 10s of cts/sec in lines planned for NUV sensitivity calibration. This may use a RASCAL aperture larger than a point-source, but not large enough to overfill the COS PSA. Exercise CDS Pt-Ne lamp-only channel Exercise CDS ND filters No absorption cell for this phase Establish confidence that both CDS and RASCAL are ready to support operations

7. 7 COS turn-on and ambient functional test Verify that COS is hooked up correctly and ready to take data Use standard version of ambient functional test. Not a calibration specific test. –Functional test may include only very short exposures with calibration subsystem lamps at this point. Count rates with COS optics and detectors are unknown. No useful data expected from internal lamps, other than that they turn on.

8. 8 Test #40 TA1 Aperture Scan RT commanding based on prior alignment phase activities Align RASCAL to COS using light prior to pump-down Adjust aim of RASCAL beam and/or COS aperture block to ensure that light enters COS PSA Use NUV TA1 time-tagged exposure (little FUV in air) Use CDS Pt-Ne lamp at 1000 cts/sec on RASCAL PMT –use ND filters + lamp current to adjust brightness Scan RASCAL steering mirror if necessary and possible –5x5 square raster for coarse alignment –11x11 cross scan for fine alignment Scan aperture block location Find combination of RASCAL steering mirror and COS aperture block that provides best illumination and good NUV image quality. This will be the starting point for measurements in vacuum.

9. 9 Example of coarse and fine scans (Can RASCAL can do this?) x x x x x 5x5 coarse raster steps ~radius of PSA find single brightest point x x x x x x x x x x x x x 11x11 fine raster steps TBD ~1/5 radius of PSA find brightest point in X and Y

10. 10 Pumpdown Final verification of COS and RASCAL readiness Shutdown Final verification of vacuum chamber and support equipment readiness Pumpdown

11. 11 Post-pumpdown verification of CDS relay optics to RASCAL entrance aperture alignment Repeat pre-pumpdown alignment check of CDS to RASCAL using reference detector Confident that CDS and RASCAL are working properly in vacuum Confident that CDS - RASCAL are properly aligned to get light into COS May be done while waiting for pressure to decrease to safe level for COS turn-on

12. 12 COS Vacuum Functional Test Wait for vacuum chamber pressure to fall below 10 -5 Torr Wait for COS internal pressure monitor to indicate safe level –10 -4 Torr before opening FUV door –10 -5 Torr for NUV HV operations –10 -6 Torr for FUV HV operations If pressure is falling slowly, can we skip FUV HV ops in FT and proceed with initial NUV activities? COS Vacuum FT to verify operability. This may be an abbreviated version of the full test. VFT may include observations of all four internal calibration lamps. Exposure times and current levels will not be optimized yet. Don’t expect much useful data.

13. 13 Tests #50 and #60 TA1 aperture scan and focus sweep RT commanding based on prior alignment phase activities Repeat RASCAL and COS aperture scans of test #40 to establish optimum centering of light into COS Use CDS Pt-Ne lamp on lamp-only channel Use fused silica long-pass filter to limit wavelengths to only NUV Use CDS ND filters and lamp current to adjust count rate Find optimum OSM1 linear stage position for NUV focus as indicated by TA1 image Update operations software for future NUV tests Time has been reserved for these activities. Details of procedures have not been defined in the calibration plan. Use Tom Delker’s HOMS procedure as starting point. Estimate 0.5 shifts for each test needed for data acquisition.

14. 14 Test #150 NUV External Pt-Ne lamp spectra Level I Spectral Resolution Level I, II Wavelength Coverage and Wavelength Scale Configure COS to aperture and OSM positions derived from results of tests #50 and #60 First COS spectra in vacuum over entire NUV wavelength range CDS Pt-Ne lamp on lamp-only channel, fused-silica filter blocks FUV RASCAL 10  m aperture for most observations Adjust count rate to ~10000 cts/sec on RASCAL detector with fused-silica filter, but no bandpass filter in place Record external spectra for each NUV grating (no FP-SPLITs), PSA –SMS operation for this phase –Use 6 setups that “paint the spectrum” for each M grating, 3 for G230L Record image of 10  m aperture with TA1 and TA1-BRT Record image of double 4  m aperture with TA1 Record spectra through 10  m aperture and BOA with G230L –RT operation for these three

15. 15 Analysis of Test #150 Plot spectra, identify lines Assess focus, 2D images, 1D line profiles, resolution Determine whether adjustments or additional measurements such as focus sweeps are needed Measure location of spectra on detector, define subarray locations Determine whether spectra of all gratings fall within the range expected to be covered by a single flat-field exposure. Derive wavelength calibration solutions Determine wavelength ranges and central wavelengths for each grating and stripe Goal is to have minimum set of 6 setup positions cover the entire wavelength region ie “paint the spectrum” Update OSM2 position tables if necessary Assess count rates for planning science calibration times Look for second order images in NUV Measure BOA/PSA transmission ratio vs wavelength Determine of double aperture images are oriented in cross-dispersion direction as desired for spatial resolution test later.

16. 16 Test #150 NUV External Pt-Ne lamp spectra Sequence and time 4 SMS’s RT No internal wavecal lamps No FPSPLITs

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21. 21 Test #250 NUV Cal Subsystem flat-field lamps 1st light Level I Flat-field Lamp Operation No external lamp, no CDS, no RASCAL operations SMS operations Move aperture block to allow spectrum of flat-field aperture to overlap region of PSA as defined by results of test #150 First measurement of count rates with calibration subsystem flat-field lamps in vacuum (unless vacuum FT provided data) Exposure times of 100 seconds should be adequate Measure NUV count rates with medium current only. High current may be a contamination risk at this early time. Measure count rates for one setup position for each “M” grating, 1850, 2250, 2850. Measure count rates in all three stripes for each grating. G185M is expected to be brightest.

22. 22 Test #250 analysis Assess suitability of nominal flat-field scheme: –NUV with G185M and either lamp at high current –Extrapolate from medium current count rates Verify that flat-field data covers location of all spectra –compare pixel region covered by these FF data with regions covered by PSA science data from test #150 Simulate combining 4 FP-SPLIT exposures if S/N allows Verify suitability for use as pixel to pixel flats if S/N allows Plan 2nd light exposures, thermal balance test measurements and science calibration phase measurements Estimate flat-field exposure times needed for flats to support science spectra with S/N = 30, 100 Check current and ND selections

23. 23 Test #250 NUV Cal Subsystem flat-field lamps 1st light Order may be adjusted to optimize operational efficiency.

24. 24 Test #325 NUV Cal Subsystem Pt-Ne lamps 1st light Level I and II Wave Cal Lamp Operation No external lamp, no CDS, no RASCAL operations SMS operations Assume 5 minutes total time for each measurement. Exposure time + overhead for mechanism movement.

25. 25 Analysis for Test #325 Plot spectra and identify lines Compare two lamps, three current levels –Any lines missing at lowest currents? –Look for bright contaminant lines or bands Derive wavelength calibration coefficients, apply to previous observations of external lamp & check accuracy Select best combination of lamp and current for wavecals of each grating setting Plan exposure times to give optimum exposure depth and number of lines for wavecals Plot lamp temperatures during operations

26. 26 Test #325 NUV Cal Subsystem Pt- Ne lamps 1st light Order may be adjusted to optimize operational efficiency.

27. 27 Test #375 Optional NUV Focus Sweeps RT operations Time is reserved for additional adjustments needed to optimize either RASCAL or COS alignments to achieve best image quality. Contents of this test will be defined after analysis of data from tests #50, #60 and #150.

28. 28 Test #450 NUV Level 1 Sensitivity Measurements Level I Spectroscopic Effective Area Level I TA1 Mode Target Acquisition RT operations Pt-Ne lamp with monochromator and RASCAL reference detector, count rate ~1000 cts/sec on RASCAL detector Use 100  m pinhole. RASCAL aperture may be larger than point source pinhole, but image may not overfill PSA. 1 for each NUV grating near expected peak sensitivity. Use a wavelength at which PMT was calibrated at LASP. If time permits additional wavelengths can be measured. Nominal instrument setup, PSA, time-tagged Validate procedures Verify sensitivity acceptable to CEI specs

29. 29 Analysis of Test #450 Derive throughput, in counts/photon, for each NUV grating Compare to range of expectations from models and component testing Compare to performance required by CEI Check for stray light artifacts away from main image.

30. 30 Test #450 NUV Level 1 Sensitivity Measurements

31. 31 Test #525 NUV External D 2 lamp spectra SMS operations. May be same SMS as used for test #150. Separate SMS for each grating. This is a D 2 lamp on the CDS lamp-only channel, not one of the calibration subsystem lamps Measure spectrum of D 2 lamp as seen with COS resolution –10  m RASCAL aperture –All NUV gratings –Use minimum number of setup positions that “paint the spectrum” Determine if extent of spectrum of CDS D 2 lamp on detector is suitable for use as flat-field data set –Largest RASCAL input aperture –G185M for NUV

32. 32 Analysis of Test #525 Plot all spectra Compare to cal subsystem spectra with same gratings to assess FCA smearing of emission line structure as measured with cal subsystem flat-field lamps in test # 250. Concatenation of data from adjacent wavelength regions allows a crude assessment of uniformity of sensitivity across segments or stripes as indication of need for “L Flats” Assess suitability of external D2 spectra with large RASCAL aperture to provide data for high S/N (~100) flat-field maps. If so, data will be taken with external lamp rather than cal subsystem lamp during ground testing. This would be done to use the external lamps rather than the internal lamps for very long exposures during ground test. RASCAL may also be defocused to provide additional blurring of the emission line structure.

33. 33 Test #525 NUV External D 2 lamp spectra 4 SMS’s 1 SMS

34. 34 Test #825 NUV FP-SPLIT Spectra Level II FP-SPLITs SMS operations Measure offsets between subexposures using one standard FP-SPLIT exposure for each NUV grating –G185M 1850, G225M 2250, G285M 2850, G230L 3000 Use CDS lamp-only channel with Pt-Ne lamp Leave lamp on for duration of test. Software should close the shutter during wavecal exposures and OSM motions. Use STScI standard wavecal exposure strategy for “auto FP-SPLIT” Use RASCAL 10  m aperture for external Pt-Ne lamp

35. 35 Analysis of Test #825 Assess algorithms for combining subexposures –The primary goal is to test the ability to combine the four subexposures without degrading spectral resolution. –Measure offsets between subexposures. Is a single constant sufficient, or is the offset dependent on grating, stripe, pixel or wavelength? –This is not intended to be a demonstration of the ability of FP-SPLITs to increase the S/N Assess auto FP-SPLIT operational procedures –Sequence of wavecal and external target exposures –Shutter operations Derive and apply wavelength scales, assess accuracy –Zero-point shift could be beam centering in aperture –Look for errors correlated with stripe, pixel or wavelength

36. 36 Test #825 NUV FP-SPLIT Spectra 1 SMS

37. 37 Test #70 FUV focus sweeps RT operations. Use procedures developed during prior alignment phases. Determine optimum positions of OSM1 rotary and linear stages to produce best focus for each FUV grating –G130M central wavelength = 1309 –G160M central wavelength = 1600 –G140L central wavelength = 1230 Use CDS Pt-Ne lamp on lamp-only channel Remove fused silica filter to allow FUV wavelengths Use CDS ND filters, FUV bandpass filters and lamp current to adjust count rate to 5000 cts/sec on RASCAL PMT Use RASCAL 10  m aperture, or 4  m if image is bright enough Update operations software for future FUV tests Estimate 0.5 shifts needed for data acquisition.

38. 38 Test #100 FUV External Pt-Ne lamp spectra Level I Spectral Resolution Level I, II Wavelength Coverage and Wavelength Scale RT operations Configure COS to aperture and OSM1 positions derived from results of test #70 First COS spectra in vacuum over entire FUV wavelength range CDS Pt-Ne lamp on lamp-only channel (no internal lamps) RASCAL 10  m aperture – close to point source Adjust count rate to ~10000 cts/sec on RASCAL detector using FUV bandpass filters in CDS, lamp current and ND filters Record external spectra for each FUV grating –1 central wavelength for each grating –no FP-SPLITs –PSA Covers full wavelength range of all FUV gratings with PSA Record external spectra through BOA with G140L

39. 39 Analysis of Test #100 Plot spectra, identify lines Assess focus, 2D images, 1D line profiles, resolution Determine whether adjustments or additional measurements such as focus sweeps are needed Measure location of spectra on detector, define subarray locations Determine whether spectra of all gratings fall within the range expected to be covered by a single flat-field exposure. Derive wavelength calibration solutions Determine wavelength ranges and central wavelengths for each grating and segment Update OSM1 position tables if necessary Assess count rates for planning science calibration times Measure BOA/PSA transmission ratio vs wavelength

40. 40 Test #100 FUV External Pt-Ne lamp spectra No use of internal wavecal lamps. No FP-SPLITs

41. 41 Test #200 FUV Cal Subsystem flat-field lamps 1st light Level I Flat-field Lamp Operation Short RT count rate check followed by SMS operations Move aperture block to allow spectrum of flat-field aperture to overlap region of PSA as defined by results of test #100 First measurement of count rates with calibration subsystem flat-field lamps in vacuum (unless vacuum FT test provided good data) Exposure times of 100 seconds should be adequate Measure FUV count rates with configuration expected to be used for routine flat-field observations

42. 42 Test #200 analysis Assess suitability of nominal flat-field scheme: –FUV seg A with G130M and either lamp at medium current –FUV seg B with G160M and either lamp at low current Verify that flat-field data covers location of all spectra –compare pixel region covered by these FF data with regions covered by PSA science data from test #100 Assess smearing of line structure in FUV if S/N allows Simulate combining 4 FP-SPLIT exposures if S/N allows Verify suitability for use as pixel to pixel flats if S/N allows Plan 2nd light exposures, thermal balance test measurements and science calibration measurements Estimate flat-field exposure times needed for flats to support science spectra with S/N = 30, 100 Check lamp current and ND filter selections Plot temperatures during exposures

43. 43 Test #200 FUV Cal Subsystem flat-field lamps 1st light Order may be adjusted to optimize operational efficiency Add RT checks to sequence

44. 44 Test #300 FUV Cal Subsystem Pt-Ne lamps 1st light Level I and II Wave Cal Lamp Operation Short RT checks of count rates, followed by SMS operations Assume 5 minutes total time for each measurement. Exposure time + overhead for mechanism movement.

45. 45 Analysis for Test #300 Plot spectra and identify lines Compare two lamps, three current levels –Any lines missing at lowest currents? –Look for bright contaminant lines or bands Derive wavelength calibration coefficients, apply to previous observations of external lamp & check accuracy Select best combination of lamp and current for wavecals of each grating setting Plan exposure times to give optimum exposure depth and number of lines for wavecals Plot lamp temperatures during operations

46. 46 Test #300 FUV Cal Subsystem Pt-Ne lamps 1st light Order may be adjusted to optimize operational efficiency Add RT checks to sequence

47. 47 Test #350 Optional FUV Sweeps RT operations Time is reserved for additional adjustments needed to optimize either RASCAL or COS alignments to achieve best image quality. Contents of this test will be defined after analysis of data from tests #70 and #100.

48. 48 Test #400 FUV Level 1 Sensitivity Measurements Level I Spectroscopic Effective Area Level I TA1 Mode Target Acquisition RT operations Pt-Ne lamp with monochromator and RASCAL reference detector, count rate ~1000 cts/sec on RASCAL detector RASCAL aperture may be larger than point source pinhole, but image may not overfill PSA. Use 100  m diameter aperture. 1 for each FUV segment near expected peak sensitivity. If time permits additional wavelengths may be meaured. Nominal instrument setup, QE grid on, PSA, time-tagged Validate procedures Verify sensitivity acceptable to CEI specs

49. 49 Analysis of Test #400 Derive throughput, in counts/photon, for each grating Compare to range of expectations from models and component testing Compare to performance required by CEI Examine 2D data for stray light artifacts away from main image

50. 50 Test #400 FUV Level 1 Sensitivity Measurements

51. 51 Test #500 FUV External D 2 lamp spectra RT operations, with careful adjustment of count rate using RASCAL detector prior to COS exposure. Use FUV bandpass filters, ND filters and lamp current. Try for ~10000 cts/sec with RASCAL PMT. This is a D 2 lamp on the CDS lamp-only channel, not one of the calibration subsystem lamps Measure spectrum of D 2 lamp as seen with COS resolution –10  m RASCAL aperture –All FUV gratings, one setup position each Determine if extent of spectrum of CDS D 2 lamp on detector is suitable for use as flat-field data set –Largest RASCAL input aperture, wide open –G130M, G160M for FUV

52. 52 Analysis of Test #500 Plot all spectra Compare to cal subsystem spectra with same gratings to assess FCA smearing of emission line structure Concatenation of data from adjacent wavelength regions allows a crude assessment of uniformity of sensitivity across segments or stripes as indication of need for “L Flats” Assess suitability of external D2 spectra with large RASCAL aperture to provide data for high S/N (~100) flat-field maps. If so, data will be taken with external lamp rather than cal subsystem lamp during ground testing. This would be done to use the external lamps rather than the internal lamps for very long exposures during ground test. RASCAL may also be defocused to provide additional blurring of the emission line structure.

53. 53 Test #500 FUV External D 2 lamp spectra

54. 54 Test #800 FUV FP-SPLIT Spectra Level II FP-SPLITs SMS operations Measure offsets between subexposures using one standard FP-SPLIT exposure for each grating, FUV –G130M central wavelength = 1309 –G160M central wavelength = 1600 –G140L central wavelength = 1230 Use CDS lamp-only channel with Pt-Ne lamp Adjust count rate to obtain > 1000 cts in each subexposure for several lines in each segment Use STScI standard wavecal exposure strategy for “auto FP-SPLIT” Use RASCAL 10  m aperture

55. 55 Analysis of Test #800 Assess algorithms for combining subexposures –The primary goal is to test the ability to combine the four subexposures without loosing spectral resolution. –Measure offsets. Is a constant value adequate, or does the offset vary with grating, segment, pixel or wavelength? –This is not intended to be a demonstration of the ability of FP-SPLITs to increase the S/N Assess auto FP-SPLIT operational procedures –Sequence of wavecal and external target exposures –Shutter operations Derive and apply wavelength scales, assess accuracy –Zero-point shift could be beam centering in aperture –Look for errors correlated with segment, pixel or wavelength

56. 56 Test #800 FUV FP-SPLIT Spectra

57. 57 Test #550 Transmission of CDS ND filters RT operations Use external CDS Pt-Ne lamp and COS low resolution gratings to measure attenuation as function of wavelength. Use RASCAL 100  m aperture Adjust count rate for 10000 cts/segment second for FUV, or well below rate at which dead-time effects are expected. Count rates with no attenuation must be reliable. Use G140L and G230L Measure each filter in CDS inventory, ND0.5, 1, 2, 3 Done at this point after analysis of test #100. Allows time for analysis of Tests 200 & 300 before executing tests 600 & 700.

58. 58 Test #550 Transmission of CDS ND filters

59. 59 Test #600 Calibration subsystem flat-field lamps 2nd light Level I Flat-field Lamp Operation SMS operations. Tests #600 and 700 may be combined into one SMS Mechanism positions, lamp currents and exposure times are updated after the “1st light” test. Use the updated configurations to take exposures according to the nominal strategy for use of the D2 lamps. This may include use of FP- SPLIT subexposures. –FUV Seg A, G130M, 1310 – 1450, either lamp medium current –FUV Seg B, G160M, 1420 – 1580, either lamp low current –NUV use G185M, either lamp high current

60. 60 Test #600 Calibration subsystem flat-field lamps 2 nd light Order may be adjusted to optimize operational efficiency

61. 61 Test #700 Calibration subsystem Pt-Ne lamps 2nd light Level I and II Wave Cal Lamp Operation SMS operations. Tests #600 and 700 may be combined into one SMS This is a place-holder for a second look at the cal subsystem Pt-Ne lamps if changes to mechanism positions, aperture position, exposure times or lamp currents were made as a result of the first light tests, and if those changes are significant enough to require confirmation. The execution and contents of this test will be contingent on the outcome of test #300, Pt-Ne lamps 1 st light.

62. 62 Test #700 Calibration subsystem Pt-Ne lamps 2nd light Order may be adjusted to optimize operational efficiency

63. 63 Test #850 COS Vacuum Functional Test as Repeatability Monitor This is a subset of the full VFT. Observations of internal wavecal an flat-field lamps are used to accumulate data from which repeatability can be assessed. SMS operation Planned opportunities for COS Repeatability Monitor –Once near end of “Initial Alignment..in Vacuum” –End of Thermal Balance at near nominal temperature –Hot 1, Cold 1, Hot 2, Cold 2 Thermal Vacuum test plateaus –During Cold 1 to Hot 2 transition –End of Thermal Vacuum test at near nominal temperature –Mid-way through Science Calibration phase –End of Science Calibration phase –TBD times at GSFC before and after critical tests or environmental exposures

64. 64 Test #850 COS Vacuum Functional Test as Repeatability Monitor