Patricia A. Hansen

Integrated approach for contamination control and verification for the Hubble Space Telescope first servicing mission

The Hubble Space Telescope is the first spacecraft designed from its conception to allow for Scientific Instrument upgrading and subsystem maintenance by using the Shuttle. Regular and contingency servicing missions preserve and broaden the scientific objectives of the HST through on-orbit maintenance. To achieve mission success for the Hubble Space Telescope First Servicing Mission, a contamination control methodology was developed and instituted by ensure that scientific instrument performance was not degraded or compromised during fabrication, build-up, ground integration and test activities, on-orbit servicing including Extravehicular Activities, or through on-orbit operational activities. The cleanliness methodology considered the effects of outgassing and surface contaminants on the degradation of the sensitive components. Through plans and procedures for handling sensitive components and the development of a detailed contamination budget extending from Goddard Space Flight Center processing through launch, the preservation of the science capabilities (as affected by contamination) was achieved.

Results of STS-51 orbiter crew compartment contamination generation and extravehicular activity (EVA) payload bay transfer experiment

Contamination witness plates were flown on STS-51 as part of a NASA Extravehicular Activity (EVA) Flight Test Experiment to quantify and identify particulate contamination generated in the Orbiter crew compartment which has the potential to contaminate the Extravehicular Mobility Units (EMUs) and transfer from the EMUs to mission critical hardware during EVAs. Particles, larger than 100 microns, were found on both witness plates, indicating transfer from the EMUs during EVAs. For missions such as the Hubble Space Telescope First Servicing Mission, where contamination critical optical elements were exposed during EVAs, the potential for particulate transfer from the crew compartment to these optical elements and the Hubble Space Telescope was evaluated.

Flight experiment to investigate microgravity effects on solidification phenomena of selected materials

A Get Away Special (GAS) experiment payload to investigate microgravity effects on solidification phenomena of selected experimental samples has been manifested for flight on STS-42. The first flight of the furnace assembly will (1) investigate the p-n junction characteristics for advancing semiconductor device applications, (2) study the effects of gravity-driven convection on the growth of HgCd crystals, (3) compare the textures of the sample which crystallizes in microgravity with those found in chrondrite meteorites, and (4) modify glass optical characteristics through divalent oxygen exchange. The space flight experiment consists of many small furnaces. While the experiment payload is in the low gravity environment of orbital flight, the payload controller will sequentially activate the furnaces to heat samples to their melt state and then allow cooling to resolidifaction in a controlled fashion. The materials processed in the microgravity environment of space will be compared to the same materials processed on earth in a one-gravity environment. This paper discusses the design of all subassemblies (furnace, electronics, and power systems) in the experiment. A complete description of the experimental materials also is presented.