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Last updated
19 February 2002 15:03:19

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ACS Ambient Ground Calibration and Verification at GSFC : Mar-Aug 2001


The major goal of this campaign is to obtain a final set of calibration and verification data in ambient environment with RAMP+RAS/Cal for the HRC#1 and WFC#4 flight detectors during ACS' last stay at GSFC. If the schedule does not permit the completion of some activities, they will be executed in a different environment, such as in the third thermal balance and vacuum campaign, TB/TV 3 (Jun-Jul 2001), or in the RAS/HOMS campaign at BATC (Oct 29-Nov 7).



The majority of the activities will be conducted in the GSFC SSDIF clean room. ACS is fully integrated and all flight detectors are in final alignment in ambient environment. For all activities, the instrument is in its flight configuration and has been fully verified. The detectors are at their nominal temperatures of -77 C for WFC and -80 C for HRC. The ceiling lights in the clean room remain on through all activities, so ACS must be wrapped in lumalloy blankets to reduce straylight. By default, the data will be acquired with MEB 1, although some data will also be obtained with MEB 2 to meet the time specifications. The default gain settings are 1 e-/DN for the WFC and 2 e-/DN for the HRC, with a bias offset of 3 for both detectors. The WFC will be read-out with all four amplifiers (ABCD) and the HRC with amp C, the least noisy of its four amps. A detailed description of the CDS and RAMP+RAS/Cal is available at Calibration Facilities, Test Apparatuses, and Stimuli.


The calibration activities for Mar-Aug 2001 are divided into several items, listed in the following table. A more detailed description of each activity, including the RAS/Cal configuration when in use, is also available. The activities result in datasets acquired internally or externally (with or without RAS/Cal) for the HRC and WFC. The estimated time to complete all the activities is 170 hours (~7 full days or 17 ten-hour days).

1. Filter Wheel Mapping None N/A SMS Improvement of the filter wheel repeatability Apr 2, 4, 5
2. Internal Flat Field Stability T2/T4 N/A RT Repeat deep internal flats at 2 epochs (Apr, Aug) and compare with Feb and Mar 2001 Apr 3, 4
3. CCD Read-out Characterization T2/T4 N/A SMS Measure gain, linearity, read-noise, bias Apr 3, 4, 9
4. HRC/SBC Confocality HD2 MgF2 Lens RT+SMS As in Sep 15, 2000 confocality Apr 5
5. Grism Characterization Ar, QTH CDS, RAMP RT Line and continuum spectra at 5 field points Apr 6
6. Prism Characterization Hg CDS, RAMP RT Line and continuum spectra at 5 field points Apr 9
7. Ext. Broad-Band Flats HD2, QTH, Diffuser OUT RT Short and long wavelength filters with HRC Apr 10
8. Internal Lamp Count Rates T1-4, D2 N/A RT+SMS Execute the "dust search" SMSs and supplement for HRC Apr 4, 5
9. CCD CTE T2/T4 N/A SMS FPR and EPER at several signal levels See TB/TV 3
10. Absolute Throughput QTH, Ext. D2 CDS, Dark, Diode RT Measure efficiency of each filter/detector combination Aug 9-15
11. Instrumental Polarization QTH, Diffuser OUT RT Use 3 broad-band filters with both UVPOL and VISPOL -
12. Polarization Efficiency/Angle QTH CDS, Dark, Diode RT Use 3 broad-band filters with both UVPOL and VISPOL at 5 field points Aug 15-22
13. FLASH Calibration FLASH LEDs N/A SMS Deep flash exposures for shutter dependence and levels See RAS/HOMS

Notes :