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Space Telescope Imaging Spectrograph
STIS-18

ACTIVITY TITLE: NUV MAMA HV Recovery

ID: STIS-18

APPLICABLE SMOV REQUIREMENTS: L.10.4.5.1.11

DESCRIPTION: This activity addresses the concerns over Cesium migration from the NUV-MAMA photocathode into the pores of the microchannel plate and lays out the procedures necessary to permit a safe and controlled recovery of the NUV-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 -1750V (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. A minimum delay of 24 hours is required for data down-linking and analysis.

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.

IMPLEMENTATION METHOD: Stored commanding

DEPENDENCIES: The first visit (signal processing test) may be done any time after STIS-04 has been completed. However, visits 2-4 should not be done until at least 36 hours after STIS-17 (FUV MAMA HV Recovery) has been completed.

DURATION: 22,000 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 would 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 wheeler@stsci.edu

DATE: 09/27/07