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From: starrfie@hydro.la.asu.edu (Sumner Starrfield) Subject: HST Servicing Mission update Date: Sat, 16 Oct 93 9:16:56 MST HST SERVICING MISSION UPDATE AND OVERVIEW OF SERVICING MISSION OBSERVATORY VERIFICATION (SMOV) By Carl Biagetti The first HST servicing mission is still on schedule with the Shuttle launch slated for 2 December 1993, at 4:30 AM, EST. Within the first two days of the mission, the HST will be readied, through a combination of on-board commands and ground commands, for capture by the Shuttle. At approximately 4 AM on Dec. 4, the Shuttle is scheduled to grapple and berth the HST. Starting on day three, the astronauts will begin a series of five EVAs, one per day, during which all the HST upgrades and repairs will be accomplished. As of this writing, the principal activities planned for each EVA are as follows: EVA 1 Rate Sensing Unit (RSU) 2 (Gyros 3 & 4) RSU 3 (Gyros 5 & 6) Magnetic Sensing System (MSS) 1 (Magnetometer 1) EVA 2 Solar Array II EVA 3 Wide Field Planetary Camera (WFPC) 2 Goddard High Resolution Spectrograph (GHRS) Repair Kit EVA 4 COSTAR Electronic Control Units (ECUs) 1 & 3 EVA 5 Solar Array Drive Electronics unit 1 (SADE-1) MSS 2 Coprocessor Fuse Plug At the end of EVA 5, the new Solar Arrays will be deployed. The current schedule calls for HST to be unberthed at 1:30 AM on Dec. 10. At 4:00 AM, the Aperture Door is opened, followed by release of HST at 5:20 AM, a little more than eight days after launch. The Servicing Mission Observatory Verification (SMOV) begins upon release of HST from the Shuttle. Planned for execution over an estimated three-month period, the SMOV has as its primary objectives the recommissioning of the HST for the resumption of science operations in as short a time as possible, and for the publication of Early Release Observations (EROs) to demonstrate the improvement in telescope performance. The SMOV period is divided into three phases: 1) the Real-Time Command Phase, 2) the Health & Safety Stored Program Command (SPC) Phase, and 3) the Science Mission Specification (SMS) Command Phase. The Real-Time Command Phase is the shortest of the three phases, having an expected duration of less than two days. It begins upon HST release from the Shuttle orbiter and consists of those basic operations that normally constitute HST recovery from PSEA Safemode [Pointing/Safemode Electronics Assembly]. These operations include, among other things, initialization of the spacecraft, attitude determination and transition to on-board attitude control, gyro bias updates, and uplink of the new ephemeris. Once the first phase of SMOV is completed, the Health & Safety SPC Load, enabling the initiation of High Gain Antenna (HGA) tracking. The Health & Safety SPC Phase is planned to last about two days, and provides for the completion of the flight software transition to support normal science activities. The third and longest of the SMOV phases is the SMS Command Phase. This phase consists of an extensive series of engineering activation and check-out of the serviced systems, including WFPC2, COSTAR and the COSTAR-corrected SIs [Science Instruments], i.e., FOC [Faint Object Camera], FOS [Faint Object Spectrograph], and GHRS. The HST OTA [Optical Telescope Assembly] is then collimated, the COSTAR Deployable Optical Bench (DOB) is deployed, and a coordinated program for optical alignment of all the SIs is begun. As each SI achieves fine alignment, a calibration program designed to recommission the SIs as quickly as possible for resumption of science operations is undertaken. At appropriate times after SI alignment and during the calibration phase, Early Release Observations (EROs) will be performed in order to provide images, and possibly spectra, of scientifically interesting targets that clearly demonstrate to the public, the media, and to the scientific community the dramatic improvement in HST performance. The entire SMOV program consists of several dozen interrelated activities that have been designed and documented in a joint effort by NASA/GSFC, the ST ScI, PIs [Principal Investigators] and IDTs [Instrument Development Teams]. The ST ScI SMOV preparation team is currently processing 82 proposals for execution during the SMOV period which, under current estimates, will require thirteen weeks for completion.
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