A limitation on the number of pointings arises from the limited on-board memory. Current specifications allow for at least 10 pointings between ground contacts (nominally every 16-30 hours between telemetry sessions). In addition, there may be a reduced number of pointings allowed during the first six months of the mission. Ground contacts last for 4-5 hours during which time no new data is taken. Raster scans can be accomplished over moderate areas of approximately 100 sq. degrees. When in use, the OXS (Objective X-ray Spectrometer) will view the sky 90 degrees from the pointing direction of the other pointed instruments. Scanning in wavelength, will require approximately 10 spacecraft attitude changes of magnitude 5-15 arcminutes for a single pointing. These attitude changes will occur no more frequently than once every 104 seconds.