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Space Telescope Imaging Spectrograph




DESCRIPTION: This activity addresses the concerns over Cesium migration from the FUV-MAMA photocathode into the pores of the microchannel plate and lays out the procedures necessary to permit a safe and controlled recovery of the FUV-MAMA detector to science.

The recovery consists of four separate and unique procedures (visits) and they must be completed successfully and in order. They are: (1) a signal processing electronics check, (2) 1st high voltage ramp-up to an intermediate MCP voltage of -1500V with limits modifications and voltage plateaus, (3) 2nd high voltage ramp-up to an intermediate MCP voltage of -1950V (300V below the nominal MCP voltage) with limits modifications and voltage plateaus followed by a fold distribution test, and (4) a final high voltage ramp-up to the full operating voltage, again with limits modifications and voltage plateaus, followed by a fold distribution test.

During the 1st high voltage ramp-up, a time-tag exposure and diagnostics are performed followed by a dark exposure. During the 2nd and 3rd high voltage ramp-ups, time-tag exposures are taken, diagnostics are performed, followed by darks, flat field ACCUMs, and fold analysis tests. Full details of these procedures will be described in a STIS TIR in preparation by Tom Wheeler.


DEPENDENCIES: To be done after STIS-04 has been completed. The first visit (signal processing test), may be executed at any time after that. However, visits 2-4 should not begin until at least 4 days after HST release following SM4, and not until at least three days after the MAMA LVPS’s have been turned on.

DURATION: 21,000 s (four full internal orbits)

DATA REQUIREMENTS: Science data to SSR and engineering telemetry.

ANALYSES & EXPECTED RESULTS: The time-tag images will be examined for unusual spatial or temporal features. Dark and images will be examined for unusual features, blemishes, and defects. The engineering telemetry data will be examined (voltages, currents, temperatures, relay position, status, and event counts) for agreement with predicted values and previous ground and on-orbit test data. Fold analysis results will be compared to predicted and previous results.

COMMENTS: A minimum delay of 36 hours is required between visits for data down-linking and analysis. Ideally one visit of this program should be scheduled every other day. The special commanding needed for this proposal will have been tested as part of the STIS System Functional Test associated with the STIS-R SMGT.

AUTHOR/telephone/email: Thomas Wheeler (410) 338-4337

DATE: 09/27/07