12.1 Introduction to the ACS
The Instrument Configurations and Operating Modes described in this chapter are used to specify exposures on the RPS2 Visit and Exposure Specifications. The legal Visit and Exposure Specifications entries are discussed in the following sections. More complete descriptions of Instrument Configurations, Modes, Apertures, Spectral Elements, etc. are available in the ACS Instrument Handbook.
Note that many of the Optional Parameters have default values. In such cases an entry as an Optional Parameter in the Visit and Exposure Specifications is necessary only if it is desired to override the default value. In the STScI proposal system, the physical units of Optional Parameter quantities are always implicit and should never be entered by the observer.
The following tables lists the permitted Instrument Configurations, Operating Modes, Apertures, Spectral Elements, and Optional Parameters for the ACS.
Table 12.1: Supported Instrument Parameters for the ACS
| Config |
Mode |
Aperture |
Spectral Elements |
Optional Parameters |
| ACS/WFC |
ACCUM |
WFC, WFC1, WFC2, WFC1-FIX, WFC2-FIX
WFCENTER,
WFC1-512,
WFC1-1K,
WFC1-2K |
See Table 12.3. |
CR-SPLIT,
GAIN,
SIZEAXIS2,
FLASHEXP |
| ACS/HRC |
ACCUM |
HRC, HRC-FIX, HRC-OCCULT0.8, HRC-CORON1.8, HRC-CORON3.0, HRC-512,
HRC-SUB1.8 |
See Table 12.3. |
CR-SPLIT,
GAIN,
SIZEAXIS2,
FLASHEXP |
| ACQ |
HRC-ACQ |
See Table 12.3,
F220W & F606W,
F220W & F550M,
F220W & F502N |
|
| ACS/SBC |
ACCUM |
SBC, SBC-FIX |
See Table 12.5. |
|
The following internal calibration targets are available for the ACS
Table 12.2: Internal Calibration Targets for the ACS
| Target Name |
Description1 |
Spectral Element |
| BIAS |
A CCD readout without an exposure (i.e., the exposure time must be specified as 0) in order to measure the detector bias. Permitted only with the ACS/WFC and ACS/HRC in ACCUM mode. GOs and GTOs should request BIAS exposures only when needed to match external subarray exposures specified via Optional Parameter SIZEAXIS2 . STScI will provide appropriate BIAS reference files for all other situations (e.g., when you specify F892N or a polarizer with a WFC exposure, or use a subarray aperture).
To ensure proper location of a subarray BIAS exposure taken to match a subarray external exposure:
- Specify the Aperture to be the same as that of the external exposure.
- Provide identical subarray Optional Parameter Specification.
- If a WFC external subarray exposure uses a ramp filter, specify the ramp filter also. See the ACS Instrument Handbook for more details.
|
DEF2
or any ramp filter in Table 12.3 |
1Use of Optional Parameters with internal targets:
1All internal target exposures will be taken as single exposures (i.e., an implicit CR-SPLIT=NO).
1Optional Parameters permitted with BIAS are:
GAIN, COMPRESSION,SIZEAXIS2.
1
2DEF means the spectral element currently in place for the ACS/WFC and ACS/HRC; and means an opaque position for the ACS/SBC.
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