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Returned Hardware

High-Speed Photometer

Astronauts remove the HSP from HST berthed in the payload bay.

Background
The High-Speed Photometer (HSP) was designed and built by the University of Wisconsin. The HSP makes photometric measurements over visible and UV wavelengths at rates up to 105 Hz. It also measures linear polarization in the near UV.

The HSP possesses five detectors - four image dissector tubes and one photo-multiplier tube. One of these detectors suffered a throughput loss of a factor of three part way through the HST mission. The detector later recovered, however, no explanation exists for why the detector anomalously failed and recovered.

Servicing Mission
During the first HST servicing mission, the HSP was replaced with the COSTAR, the Ball Aerospace/Goddard Space Flight Center (GSFC) corrective optics. According to the shuttle crew, the lip of the HSP rubbed on the multi-layer insulation (MLI) blanket during HSP deintegration from HST. Aside from the HSP rubbing the MLI, the HSP came out easily from the bay with a slight pitch up, which was expected. The bay of the HSP/COSTAR looked pristine and there was good visibility in the chamber with the HSP removed. The astronauts noted that the latch lubrication appeared to be fairly well distributed.

Post-flight Investigations
The HSP operated as it did during prelaunch testing with no detectable degradation. No physical change was observed in the appearance of the HSP, except for the nominal, anticipated creep of the Bray oil Rivet lubricant. The Bray oil migration was no more extensive than previously observed before launch. One of the latch fittings was nicked during either installation or removal. The interior of the HSP was in excellent condition. In addition to the visual inspection, the HSP was examined for contamination. A swab sample was taken on 1/25/94 from the top of the HSP, which reveals traces of oxides and barely detectable hydrocarbons. Tape lifts from the top and side of the HSP were similar to prelaunch findings.

Results of Completed Tests

  • The HSP has undergone thorough electrical testing, including EICIT, IVT, aliveness, and short and long form functional tests using the same electrical GSE used for the preflight tests. All results were nominal, including redundant units which were never exercised during the mission, and the results were in agreement with prelaunch results.
  • A throughput test was performed using a simple "flat" field source and no changes were observed.
  • Both eddy current and ultrasonic tests were performed to determine if any stress corrosion cracks had appeared in the HSP structure (near the plate fittings) since similar tests were performed before launch. The HSP structure was made from 2024 Aluminum. Post-retrieval tests showed no cracks, and verified features (e.g. repair plug) found in previous testing.
  • The HSP envelope dimensions and position of the focal plane were measured and verified. No changes were noted from preflight data.
These details about the environment and deintegration process of the HSP are important aspects of the total examination of the HSP. Other examinations include a continued external inspection. This includes rinses, tape lifts, and removal of the witness mirror from its inside protective enclosure. The latches will be inspected, a sample of the Braycote lubricant gathered and the box exterior surfaces will be closely examined, especially in the area near the aperture. This process will be videotaped for documentation. The exterior survey will be performed according to an approved procedure, a modification of the existing COSTAR metrology procedure, and will implement the AIMS systems. The aft strip, guide block mounting bracket, and all six exterior surfaces will be examined. The HSP envelope dimensions and position of the focal plane have been measured and its position verified. The internal inspection includes removal of one side panel and internal wipes, tape samples and rinses. Close inspection and photos of all filters will be completed. A witness mirror will be installed inside of HSP to monitor ground contributions to the already existing contamination. One or more flight mirrors will be removed for analysis. The side panel will be reinstalled after the internal investigation is completed.

Status as of December 1994
The HSP was shipped to the University of Wisconsin at Madison Space Astronomy Lab to undergo further testing. Prior to shipment, the HSP RIUs and latches were removed along with one filter aperture assembly which is to undergo transmission tests.

Future Plans
  • Remove tape samples from front bulkhead for GSFC contamination analysis.
  • Complete postflight testing and calibration.
  • Verify polarizer orientation.
  • Perform thermal sensor calibration.
  • Perform subsystem tests.
  • Test electronic boxes: function & temperature.
  • Detector testing: VIS tube investigation.
  • Selective internal visual inspection.
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