This document provides detailed technical information about the Spectrum-X Gamma Observatory and the scientific instruments available to U.S. astronomers who wish to propose for SXG observations. This information is intended to allow proposers to identify sources appropriate for scientific study with SXG, determine when specific sources can be observed, and assess the feasibility of proposed observations. The SXG spacecraft is shown in Figure 1 .
Moveable sleds allow the selection of four different focal plane instruments for each telescope.
Each detector is circular with a FOV of and the array is hexagonal with a total FOV diameter of . SXG will be launched into a deep, highly eccentric orbit with a period of approximately four days. The orbital parameters at the beginning of the mission are listed in Table 1 . 500 km Altitude at Apogee 199,000 km Ground station operations will take place every 18 to 30 hours. As experience grows, it should be possible to plan for at least 10 re-orientations of the spacecraft per 24 hour period.