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