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Space Telescope Imaging Spectrograph
STIS-24

ACTIVITY TITLE: NUV MAMA Spectroscopic Image Quality

ID: STIS-24

APPLICABLE SMOV REQUIREMENTS: L.10.4.5.3.4

DESCRIPTION: This proposal will measure the NUV spectroscopic PSF along the length of a long slit. It will do this by observing a point source with the 52X0.1 aperture and the G230L grating, using a three-point centered Perpendicular-to-Slit dither pattern with 0.1” spacing to observe the target both in and just out-side of the aperture. This three-point pattern will be done at six different positions along the length of the aperture, including both the nominal centered aperture position and the D1 aperture position, which is located at a position of low FUV dark current. A single centered exposure will also be taken through the photometric 52X2 aperture to provide a reference for estimating the small slit throughput. Sufficient targets will be provided to allow this test to be executed at any time during the BEA period.

IMPLEMENTATION METHOD: Stored commanding

DEPENDENCIES: Should follow STIS-11 (external focus check) and STIS-22 NUV (Optical Format Verification). This program should be deferred if there is evidence that adjustment of STIS corrector or the HST secondary is required.

DURATION: 2 External Orbits

DATA REQUIREMENTS: 1.3 Gbits

ANALYSES & EXPECTED RESULTS: The PSF quality will be evaluated in a number of ways. The centered spectra through the 52X0.1 aperture will be compared with the 52X2 reference spectrum to estimate the aperture throughput vs. position. The cross-dispersion profile observed for each centered spectrum will be compared with previous observations and PSF models. The fractional flux seen in the exposures offset perpendicular to the aperture will be used as a check of the PSF in the dispersion direction. STIS IDT IDL tools will be used with assistance of Don Lindler to analyze the data.

COMMENTS:

AUTHOR/telephone/email: Ted Gull/301-286-6184/ Theodore.R.Gull@NASA/GSFC

DATE: September 27, 2007