Artist's rendering showing the configuration of one of the Tracking and Data Relay Satellites (TDRS-H, I and J) that Hughes Space and Communications Company is building for NASA. The National Aeronautics and Space Administration ordered the spacecraft in 1995. They are medium-power versions of the Hughes 601 model, with two panels on each wing covered with silicon solar cells to provide 2,300 watts of power. Each satellite has two 15-foot-diameter single-access antennas, using Hughes' patented 'spring back' design. Each is able to simultaneously transmit and receive, enabling the spacecraft to carry on two independent two-way communications functions. In addition, there is an S-band phased array antenna that can receive signals from five spacecraft simultaneously, and a second S-band phased array antenna for transmission. An omnidirectional antenna, which handles communication, command and control signals, projects from the satellite. TDRS-H, the first in the series, is scheduled to be launched in 2000.