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The Observatory has three major parts: (1) the X-ray telescope,
whose mirrors will 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 will be achieved after deployment by a
built-in propulsion system which will boost the observatory to a
high earth orbit as shown above. This orbit, which will have the
shape of an ellipse, will take the spacecraft more than a third
of the way to the moon before returning to its closest approach
to the earth of 10,000 kilometers (6200 miles). The time to
complete an orbit will be 64 hours and 18 minutes.
The spacecraft will spend 85% of its orbit above the belts of
charged particles that surround the Earth. Uninterrupted
observations as long as 55 hours will be possible and the overall
percentage of useful observing time will be much greater than for
the low earth orbit of a few hundred kilometers used by most
satellites.
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