The Chandra Advanced X-ray Astrophysics Facility was one of NASA’s four Great Observatories (along with Hubble Space Telescope, Compton Gamma Ray Observatory, and the SIRTF). Chandra will study the composition and nature of galaxies, stellar objects and interstellar phenomena as well as basic issues in theoretical physics using the most sensitive X-ray telescope ever built. The IUS under-performed and placed Chandra in an orbit about 900 km lower than planned. Therefore Chandra's own IPS propulsion system had to be used to make up the difference. The first such manoeuvre was at 01:11 GMT on July 25 when the IPS engines fired for 5 minutes to raise perigee to 1192 km. Further perigee burns on July 31, August 4, and August 7 raised the orbit to its final 10,000 km x 140.000 km.
Chandra/IUS-27 was deployed from Columbia at 11:47 GMT July 23. At 12:48 GMT the IUS-27 SRM-1 motor fired for 125 seconds to enter a 226 km x 13841 km x 28.5 degree orbit. The SRM-1 then separated and SRM-2 fired at 12:51 GMT for 117 seconds. Chandra deployed its solar arrays at 13:22 GMT, and SRM-2 separated from Chandra at 13:50 GMT. Chandra was in a 330 x 72,030 km x 28.45 degree orbit.