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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
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