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The objectives of Hubble Servicing Mission 3A (the third servicing mission since launch) are to replace failed gyroscopes, restore other original capability, make life-extending changes, and improve HST's productivity. These activities are consistent with Hubble's design philosophy: science instruments and spacecraft components with improved or expanded capabilities are installed to take advantage of state-of-the- art advances, and spacecraft components are replaced as they age.
The payload complement for the mission includes two categories of items:
Category 1. Gyroscopes:
� Six gyroscope replacements (gyroscopes are packaged in "Rate Sensor Units," 2 in each unit for a total of 3 units)
Category 2. Spacecraft maintenance items:
� Six battery charging Voltage/Temperature Improvement Kit installations
� Fine Guidance Sensor replacement
� Multi-Layer Thermal Insulation repair
� Replacement of the central computer with an Advanced Computer
� S-Band Single Access Transmitter replacement
� Tape recorder replacement with a Solid State Recorder
Success Criteria:
For the mission to be considered fully successful, the following flight hardware must be installed:
- six operational gyroscopes,
- six voltage/temperature improvement kits,
- the advanced computer, and �
- the fine guidance sensor.
The remaining Category 2 items will be installed on a time-available basis. Items
that are not completed will be rescheduled for a subsequent Hubble servicing
mission.
The criteria for minimum mission successare that upon release from the shuttle:
* Hubble has 5 operational gyros, at least 4 of which are newly installed.
Signatures:
Dr. John H. Campbell
Associate Director of Flight
Projects for HST
Goddard Space Flight Center
John D. Holt
Mission Director for HST
Johnson Space Center
Alphonso V. Diaz
Center Director
Goddard Space Flight Center
George W. S. Abbey
Center Director
Johnson Space Center
Dr. David S. Leckrone
HST Project Scientist
Goddard Space Flight Center
Dr. Harley Thronson
Origins Science Program Director
(Acting)
NASA Headquarters
Kenneth W. Ledbetter
Director, Mission and Payload
Development Division
NASA Headquarters
Dr. Edward J. Weiler
Associate Administrator
Office of Space Science
NASA Headquarters
Back to Servicing Mission 3A Overview
