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Space Telescope Imaging Spectrograph
STIS-09

ACTIVITY TITLE: STIS to FGS Alignment

ID: STIS-09

APPLICABLE SMOV REQUIREMENTS: L.10.4.5.2.1

DESCRIPTION: This activity may be done in two parts. The first visit will be during the BEA period and will be used to verify that the alignment of STIS with the FGSs is good enough to allow subsequent SMOV activities to continue. Only a single astrometric target need be in the STIS CCD FOV. The second visit will be done using an astrometric star field such as NGC 188, and will attempt to measure the STIS to FGS alignment as accurately as possible; this field should be chosen so that multiple astrometric targets are visible in each image. If the SMOV sequence and BEA restrictions permit the second visit of this activity to be done sufficiently early, it may be used in place of the first visit.

In both cases STIS 50CCD imaging observations will be done at several dither positions, including significant offsets in the V2 and V3 directions. Each visit will end with a 50CCD ACQ exposure to verify the pointing and to measure the offset between the STIS aperture and STIS CCD detector planes.

Both the target stars and all guide stars used for each visit should, if possible, have positions known to 30 mas or better. For the first visit, sufficient targets will be specified to ensure that at least one is always available in the BEA. For the second visit the preferred target will be the same pointing in NGC 188 that was used for initial STIS-to-FGS alignment and for subsequent checks (programs 7065, 7133, 7660, 8503, etc.).

IMPLEMENTATION METHOD: Stored commanding.

DEPENDENCIES: This activity may execute any time after the CCD Functional Test STIS-06, but this program need not wait for downlink or analysis of that data.

DURATION: 2 Orbits (external)

DATA REQUIREMENTS: 0.7 Gbits.

ANALYSES & EXPECTED RESULTS: The stellar positions in the images will be determined with respect to the detector field of view, taking into account any MSM offset measured by the ACQ lamp image. The location of the STIS reference aperture in V2-V3 coordinates and the rotation angle with respect to the FGS reference frame will be determined. PDB and SIAF updates will be made as needed, but these updates may be deferred until after the data from the second visit of this program have been analyzed, unless it is determined that an earlier update is required to support SMOV operations. May require coordinating with TEL branch personnel to compute any table updates.

COMMENTS:

AUTHOR/telephone/email: Charles Proffitt/410-338-4938/proffitt@stsci.edu

DATE: September 21, 2007