KEYWORDS: Gyroscopes, Space telescopes, Telescopes, Space operations, Transmitters, Stars, Sensors, Hubble Space Telescope, Visibility, Current controlled current source
Without an additional Hubble Space Telescope (HST) Servicing Mission (SM4), the HST Project will face numerous challenges to keep the telescope operating for as long as possible. As part of SM4, the HST Project planned to install various upgrades to the telescope including the installation of new batteries and new rate integrating gyros. Without these upgrades, reliability analyses and trend projections indicate that the spacecraft will lose the capability to conduct science operations later this decade. The HST team is being challenged to maximize the telescope's remaining operational lifetime, and also maximize its science output and quality.
The two biggest areas of concern are the age and condition of the batteries and gyros. Together they comprise the largest risk to telescope productivity and safety and present the biggest challenges to the HST team. The six nickel-hydrogen (NiH2) batteries on HST are the original batteries from launch. With fourteen years of operational life, these batteries have -lasted longer than those on any comparable mission. Yet as with all batteries, their capacity has been declining. Engineers are examining various methods to prolong the life of these mission critical batteries, and retard the rate of degradation.
In addition to the batteries, the National Aeronautics and Space Administration (NASA) scheduled all six gyros to be replaced on SM4. Two of the six gyros have already failed, leaving four available for operational use. To be able to conduct science operations, the telescope currently needs three gyros. Efforts are underway to enable a guiding mode that will require only two gyros. In this mode, however, science target scheduling will be strongly driven by new factors (such as star tracker availability), which may ultimately reduce science gathering efficiency. The status on this effort and its potential impact on science operations will be discussed.
This paper will focus on these and other efforts to prolong the life of the HST, thus enabling it to remain a world-class observatory for as long as possible.
KEYWORDS: Space operations, Hubble Space Telescope, Space telescopes, Local area networks, Instrumentation engineering, Graphic design, Human-machine interfaces, Optical instrument design, Observatories, Buildings
An important aspect of the Hubble Space Telescope (HST) operations is the ability to quickly disseminate and coordinate spacecraft commanding and ground system information for both routine spacecraft operations and Space Shuttle Servicing Missions. When deviating from preplanned activities all new spacecraft commanding, ground system and space system configurations must be reviewed, authorized and executed in an efficient manner. The information describing the changes must be disseminated to and coordinated by a large group of users.
In the early years of the HST mission a paper-based Operational Request System was used. The system worked, but was cumbersome to efficiently coordinate with a large geographically dispersed group of users in a timely manner. As network and server technology matured, the HST Project developed an on-line interactive Operations Request System. This Operations Request System is a server-based system (access via HST Net) that provides immediate access to command and ground system information to both local and remotely based Instrument Engineers, Flight Operations Team Controllers, Subsystem Engineers and Project Management.
This paper describes the various aspects of the system's submission, review, authorization and implementation processes. Also described is the methodology used to arrive at the current system design and the Graphical User Interface (GUI). This system has been used successfully for all routine and special HST operations for the last five years. This approach to operations coordination is adaptable to spacecraft of any complexity.
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