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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.
Chandra's
improved sensitivity can make possible more detailed studies of black
holes, supernovas, and dark matter and increase our understanding of
the origin, evolution, and destiny of the universe.