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The AXAF Orbits (Erratum to Issue 1)

In ``The AXAF Orbits'' in issue 1 of this Newsletter, the baseline AXAF-I orbit was erroneously stated to be elliptical with initial semi-major axis 55,000 km, eccentricity 0.818, inclination , ascending node at right ascension , and an orbital period of 35.6 hours. The semi-major axis, eccentricity, and period were based on maximum and minimum geocentric distances of 10,000 and 100,000 km. In fact, the design orbit has minimum and maximum altitudes of 10,000 and 100,000 km, so that the AXAF-I orbit has an initial semi-major axis of 61,400 km and eccentricity 0.733, with an orbital period of 42.1 hours. The longest continuous viewing time for a source at elevations above the high-radiation part of the orbit is about 31 hours.

It has recently become likely that the final orbit reached will have minimum and maximum altitudes of 10,000 and 140,000 km, giving an orbital period of 64.3 hours, and allowing low-radiation exposures as long as 54.4 hours.