Hubble Space Telescope

(HST) Archive System

NASA Langley Research Center
Hampton, Virginia

Returned Hardware

Orbital Replacement Units

Hubble Space Telescope servicing missions are scheduled at approximately three-year intervals to replace scientific instruments, as well as batteries and other limited-life items. Ranging in size from a shoebox to a telephone booth, most of the items can be removed or installed with the aid of wrenches and screwdrivers. These items, called Orbital Replacement Units, include components in the guidance and control systems and in the command and data handling system, a computer, solar arrays, and the scientific instruments. Instruments, batteries, computers, and other essential components in the equipment bays are accessible through doors for easy removal and replacement.

Altogether, some 70 items in the HST can be replaced in orbit. The Orbital Replacement Units are:

1. Scientific Instrument Control and Data Handling
2. Faint Object Camera
3. Wide Field / Planetary Camera
4. Data Interface Unit for Optical Telescope Assembly
5. Data Management Unit
6. DF-224 Computer
7. Fine Guidance Electronics (3)
8. Battery (6)
9. Fixed Head Star Tracker (3)
10. Rate Sensor Unit (3)
11. Charge Current Controller (3)
12. Data Interface Unit for Support Systems Module
13. Electrical Power Thermal Control Electronics
14. Power Control Unit
15. Power Distribution Unit
16. Fuses (14)
17. Multiple Access Transponder (2)
18. Single Access Transmitter (2)
19. Faint Object Spectrograph
20. Fine Guidance Sensor (3)
21. Reaction Wheel Assembly (4)
22. Solar Array (2)
23. Low Gain Antenna
24. Sun Sensor

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