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| HST Orbital Systems Test Platform (HOST) |
| Payload Bay |
| 2,800 lb |
| Prime: Scott Parazynski |  |
| Backup: Stephen Robinson | |
| Overview |
| The Hubble Space Telescope (HST) Orbital Systems Test (HOST) platform is an on-orbit test bed for hardware that will be installed on the orbiting telescope during the third HST servicing mission. The primary objective of the HOST mission is to demonstrate that electronic and thermodynamic equipment slated for installation on the Hubble Telescope in 1999 works in the radiation and microgravity environment. Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) One of the primary pieces of equipment to be tested is a new cooling system for the Near-Infrared Camera and Multi-Object Spectrometer, or NICMOS, that will extend the instrument's operational life at least five years. The NICMOS cooling system--a reverse turbo-Brayton cycle cooler and capillary pump loop--is a significant advancement in technology that may eliminate cooling systems that depend on Dewars to supply supercold liquids for cooling sensors. NICMOS consists of three cameras that take pictures of objects at the far reaches of the universe. It can see objects created near the beginning of the universe and can look deep into clouds of dust to view how stars and planets are formed. NICMOS is also a spectrometer, a coronagraph, and a polarimeter. NICMOS was installed on the Hubble Space Telescope on the second servicing mission in February 1997. It replaced the Faint-Object Spectrograph. New Data Processor (DF-224) The HOST mission will also test whether a new computer scheduled to be placed on the Hubble Telescope next year will operate in the radiation environment of space. The 486 computer will have twice the memory and three times the processor speed of the DF-224 computer and its coprocessor that it will replace. In addition to providing a measure of the 486 computer's performance, the HOST mission will also demonstrate the ability of the computer's hardware and software to handle errors. The DF-224 computer has experienced a number of memory card failures and a few errors thought to have been caused by radiation. The HOST mission will allow investigators to discover any parts that are susceptible to radiation or single-event upsets. It will also demonstrate the 486 computer's handling of radiation-induced errors. The pulse height analysis instrument will measure the actual radiation levels of heavy ions that cause single-event upsets in electronic devices. This information will be used to update the present models and aid in mapping the space environment. The improved models and maps can then used to predict the frequency and intensity of SEUs. Solid State Recorder (SSR) A solid-state recorder that will replace the engineering science tape recorder as a flight spare on the Hubble Space Telescope will be tested during the HOST mission. The purpose of this test is to determine if the SSR is equivalent to the unit now on the Hubble Telescope, if the Hubble's current recorder is abnormal, and if the HOST SSR will operate properly on Hubble. Errors were detected in the flight unit recorder on the telescope after it was installed during the second servicing mission. It is believed the errors were caused by single-event upsets or transients caused by high-energy protons in the South Atlantic Anomaly. The errors were not considered serious, but minor changes have been made in the SSR software to all but eliminate the chance that the recorder will lose science data. The current recorder on the Hubble has a second-order effect that appears to be induced by the initial errors and causes a second error. No explanation for this second error has been developed, and it may be unique to the Hubble recorder. The HOST will fly a second SSR to determine if it behaves similarly. The HOST solid-state recorder will provide a very good comparison of the radiation levels in the Hubble Telescope and HOST orbits. Although the HOST mission environment is expected to be more benign than that of the Hubble orbit, the number of errors the recorder experiences in the HOST orbit will allow investigators to make a direct comparison of the two radiation environments. Fiber Optic Performance HOST will also analyze the performance of fiber optics in the orbiter by transmitting telemetry data to the orbiter over standard data lines and fiber-optic lines. The two data streams will be recorded for postflight analysis. Fiber-optic transmission is being considered for use on the orbiter to improve payload processing and to enable faster orbiter ground processing. HOST Support Equipment The platform for the HOST hardware is an airborne support equipment cradle originally designed to carry the Upper Atmosphere Research Satellite on STS-48 and now used as a carrier for contingency deployment and repair hardware. Protective enclosures, miscellaneous equipment, and honeycomb face sheets have been removed from the cradle and reconfigured to accommodate the HOST avionics and experiments. |
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Editorial Contact Ed Campion
Technical Contact USA Web Master
