Cycle 1 Calibration - FGS

The activities listed below are those parts of the Cycle 1 Calibration plan for the Fine Guidance Sensor (FGS) that have a dedicated observational component.  It is important to remember that the Cycle 1 Calibration plan is not final.  The plan as laid out here is based on our current understanding of the telescope, instruments, and all other planned observations in Cycle 1.  This program should be considered provisional and may change in response to system developments and the final science program. 

The text for each calibration activity below includes a title, program ID number, and the abstract also included with the APT file.  The program ID number links directly to the STScI webpage for that program.  Users interested in obtaining APT files can either follow that link or retrieve the file by running the APT and retrieving it by its program ID.

Program 1534 - CAL-FGS-002 - Geometric Distortion and Scale

Program 1535 - CAL-FGS-003 - Internal Lamp Flat Field

Program 1534 - CAL-FGS-002 - Geometric Distortion and Scale

This proposal monitors the geometric distortion & pixel scale of both FGS Guide channels. The LMC astrometric field is imaged via FGS in calibration mode, obtaining full frame images at 5 different positions within the astrometric field for each of the two channels. The mid-point of the catalog will be placed at the center of the FGS channel being calibrated (the other channel will be guiding). This will ensure that (1) the same stars are used to calibrate FGS1 and FGS2, and (2) we will thus obtain an accurate measure of the relative sensitivity of Guiders 1 & 2.This program is similar to CAR-FGS-011.

Epoch 1 observations should be done within 5-7 months of the end of commissioning. Epoch 2 observations should be done within 5-7 months of the epoch 1 observations.

Program 1535 - CAL-FGS-003 - Internal Lamp Flat Field

This will monitor the flat field of the FGS channels. There is significant structure in the lamp flats, however, these lamp flat fields are good for monitoring trends in the response of the detector over time. The internal calibration lamp shall be used, so Fine Guiding will not be possible, hence ACS will be under coarse control. Exposures will use full frame images. Each exposure is repeated five times for cosmic ray rejection. After the full frame data are obtained, a 1 arcminute telescope offset is to be executed and the imaging sequence is to be repeated to allow for sky-source removal (the FGS has no shutter or opaque element).

Epoch 1 observations should be done within 5-7 months of the end of commissioning. Epoch 2 observations should be done within 5-7 months of the epoch 1 observations.



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