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

GOAL :

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).

LOCATION AND DATE : GSFC/SSDIF : Mar-Aug 2001

INSTRUMENT CONFIGURATION :

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.

CALIBRATION ACTIVITIES :

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).

ITEM	STIMULUS	RAS/Cal CONFIGURATION	COMMAND	COMMENTS	EXECUTION DATE

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 :

N/A : The data is acquired internally so RAS/Cal is not needed.
OUT : RAS/Cal is removed from the light path to position an external light source.
The command mode is either in real-time (RT) with the CCL or with stored command sequences (SMS).
HD2 : external Hamamatsu deuterium lamp (<3500 Ang). Note : The CDS does not have an Hamamatsu deuterium lamp.
T1, T2 : WFC internal tungsten lamps. T2 is the default.
T3, T4 : HRC internal tungsten lamps. T4 is the default.
D2 : Internal deuterium lamp for the HRC blue filters (or SBC if in use).
CDS : Calibration Delivery System

MISCELLANEOUS :