Q&A: Chandra Mission

Q:
How hot does Chandra get? What materials do you use to protect the sensitive instruments on board?

A:
Thermal control is primarily passive, using thermal coatings and multilayer insulation blankets. On-board-computer-controlled electrical heaters augment these passive elements to maintain sensitive items such as the mirror assembly at a nearly constant temperature near 70 degrees Fahrenheit. The focal plane of the scientific instruments such as ACIS is kept much cooler, at a temperature of about -150 degrees Fahrenheit.

Viewing is restricted to angles larger than 47 degrees from the limb of the Sun. This restriction makes about 15% of the sky inaccessible on any given date, but no part of the sky is ever inaccessible for more than 3 months.

Another danger to the instruments is the radiation belt around the Earth, which contains a high concentration of charged particles that could damage the telescope. Although the spacecraft has mechanical and magnetic baffles designed to prevent low-energy electrons from striking the instruments, the ACIS instrument is stowed in a safe configuration during radiation belt passage.

See also: http://chandra.harvard.edu/about/spacecraft.html & http://chandra.harvard.edu/about/specs.html