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Updates on COS Development Status and Testing Activities for NASA's Space Telescope

This report details the progress and findings from the COS (Cosmic Origins Spectrograph) development and testing phases from January to October 2003. Key integration milestones include successful calibration platform installation, FUV detector testing and alignment, initial thermal vacuum tests, and identification of performance issues during integrated instrument assessments. Science calibration and data processing activities are outlined, emphasizing ongoing improvements in spectral resolution and throughput. Additionally, instrumentation adjustments have been made to address encountered challenges.

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Updates on COS Development Status and Testing Activities for NASA's Space Telescope

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  1. SPACE TELESCOPE SCIENCE INSTITUTE Operated for NASA by AURA TIPS21 August 2003 (Last COS TIPS: Dec 2002) An Update on the COS Development Status COS Integrated SI (Aft End)

  2. COS Timeline Summary • Instrument integration activities (Jan-Mar 2003) • Calibration platform installed, electronics, enclosure, etc • FUV02 (flight spare) detector qualifications completed • FUV detector swap and alignment (March-April 2003) • FUV02 performance better at longer l; “flatter” throughput • Alignment checked under N2 purge with CAOS/HOMS • Environmental tests of integrated instrument (April 2003) • GSFC: EMI/EMC, acoustics, vibration, metrology • Initial thermal balance, alignment, and testing in vacuum completed in July 2003 • To confirm focus/spectral resolution/throughput/operations

  3. COS Timeline Summary (con’t) • Instrument currently out of vacuum chamber at Ball • Working issues discovered during initial testing • T-Vac activities to begin September 11 • Science calibration to occur September 18 - October 12 • Delivery to GSFC expected in late October 2003 • Integrated pipeline testing in May 2004 • SMGT planned for late July 2004 • Working to launch date of May 2005

  4. COS: pre-acoustic test; packing for return to Ball

  5. COS Integrated SI and Enclosure

  6. COS Issues of Interest • Spectra in Bright Object Aperture (BOA) have coma • ND2 filter (2 mm cube) has 0.25o wedge • Resolution degraded by factor of ~4 in NUV, less in FUV • No serious science impact • Spectral lines sometimes found to be “tilted” under N2 purge in CAOS/HOMS after FUV02 detector swap • Time variable, observed for FUV external lamp spectra • Most likely related to failing PtNe calibration lamp • Not seen after new lamp installed or in later vacuum tests

  7. Removal of COS from Vacuum Chamber • Internal ion pressure gauge not functioning • Problem traced to incorrect signals fed to electronics box; fixed • RASCAL chief ray not aligned as it was prior to pump down • Chief ray remeasured; tip/tilt mirrors corrected • Interpoint converter found to be faulty after check of calibration lamp voltage and current telemetry • LVPS board removed, x-rayed at GSFC • Solder leads lift from solder joints under vacuum • Other converters (5) x-rayed to ensure sufficient strain relief • Spares also being checked • Stiffener plates (Kovar) being bonded to tops to prevent stress

  8. STScI Thermal Vacuum Activities • Instrument scientists supported initial science verification activities in late June - early July in Boulder, CO • Hartig, Leitherer, Sembach participated on-site • Friedman analyzed spectral repeatability data • Approx. 500 datasets produced in two week period • Science calibration data archived in MAST • All data run through OPUS and initial CALCOS processing • T-Vac retrieval screen available • Automated data transfer algorithms developed and implemented • Data also stored locally on COS machines for rapid analysis • Keyword consistency checking • Fidelity of FITS keywords being checked with help from Rose/Hodge

  9. COS Initial Testing Summary • Instrument is performing as expected optically • Spectral resolution ~ 20,000 in medium resolution modes • Throughput meets/exceeds CEI specifications • Geometric distortion can be corrected accurately • Grating motion repeatability is as good as expected • Spatial resolution ~ 1 arc sec • Final calibration activity plan being finalized by CU/Ball • Close cooperation with STScI • Testing to resume in mid-September

  10. Sample COS FUV Spectrum External PtNe calibration lamp (no distortion correction)

  11. Sample COS NUV Spectrum External PtNe calibration lamp

  12. Initial FUV Spectral Resolution Results - G130M External PtNe calibration lamp R = l/

  13. Initial FUV Spectral Resolution Results - G160M External PtNe calibration lamp R = l/

  14. Initial NUV Spectral Resolution Results G185M External PtNe calibration lamp R = l/ G225M G285M

  15. Initial COS Efficiency Estimates From Wilkinson et al. (2003, SPIE)

  16. Initial Spatial Resolution Results TA1 Image (NUV) Double pinhole aperture 1” (~40 pixels) separation 40 30 Dispersion (pixels) 20 Images are clearly resolved 10 0 10 20 30 40 50 60 Cross Dispersion (pixels)

  17. Initial FUV Grating Motion Repeatability Results

  18. Initial NUV Grating Motion Repeatability Results

  19. STScI Ground System Development and COS Pipeline • Bright object screening tool (ROBOT) in progress • Flatfield commanding rework complete • HST data volume study • COS on-orbit and pipeline estimates updated • Bench testing of command certification SMS (T. Wheeler) • Planning of Integrated Pipeline Test started • COS Pipeline (CALCOS) • Most modules are now complete • Spectral merging procedures for FP-POS positions in progress • Testing to occur on integrated SI data from T-Vac

  20. SMOV & SMGT • Successful SMOV4 requirements review 30 July 2003 at GSFC • Special commanding definition required by Oct 2003 • COS Operations Working Group will establish requirements • SMOV activity summaries (Phase 1 proposals) definition Nov-Dec 2003 • Review presently scheduled for late Jan 2004 • SMGTnow planned for late July 2004

  21. STScI User Support • STScI Instrument Division COS Staff • IS: Keyes, Sembach, Friedman; DA: McMaster • Leitherer transferred from COS to JWST in July 2003 (supporting T-Vac) • COS Handbooks • Mini-handbook for Cycle 13 being revised (August 2003) • Instrument handbook outline exists, work to continue after T-Vac • COS Exposure Time Calculators • Spectroscopic ETC software development in progress • Target acquisition ETC requirements delivered to APT group • Completion of ETCs expected in January 2004 • COS Website • http://www.stsci.edu/instruments/cos

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