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The Chandra Mission
The Observatory has three major parts: (1) the
X-ray telescope, whose mirrors focus X-rays
from celestial objects; (2) the
science instruments which record the X-rays
so that X-ray images can be produced and analyzed; and (3) the
spacecraft, which provides the environment necessary for the telescope
and the instruments to work.
Chandra's unusual orbit was achieved after deployment
by a built-in propulsion system which boosted the observatory to a high
Earth orbit. This orbit, which has the shape of an ellipse, takes the spacecraft
more than a third of the way to the moon before returning to its closest
approach to the Earth of 16,000 kilometers (9,942 miles). The time to complete
an orbit is 64 hours and 18 minutes.
The spacecraft spends 85% of its orbit above the belts of charged particles
that surround the Earth. Uninterrupted observations as long as 55 hours
are possible and the overall percentage of useful observing time is much
greater than for the low Earth orbit of a few hundred kilometers used by
most satellites. |
