The third-generation Defense Satellite Communications System (DSCS III) space segment is uniquely suited for its military mission, with anti-jam capability and sophisticated survivability enhancement. Providing uninterrupted secure voice and high data rate communications, the DSCS III satellites support globally distributed Department of Defense users. The payload includes six independent SHF transponder channels covering 500 MHz of bandwidth. Three receive and five transmit selectable antennas provide for earth-coverage, area-coverage, and/or spot beams. A special-purpose (AF-SATCOM) single-channel transponder is also on board. The spacecraft serves all branches of the Defense Department coordinated by the Defense Communications Agency. Astro Space is responsible for the satellite design, test and fabrication, under contract to the U.S. Air Force. The last four remaining DSCS III satellites have been modified for the Service Life Enhancement Program (SLEP). The purpose SLEP is to enhance the performance of all six channels to a minimum level of 50 watts of the last four DSCS satellites. In conjunction with this performance enhancement effort, each SLEP satellite will be modified with improved Low Noise Amplifiers (LNAs) which will minimize the re-radiated noise from low Effective Isotropic Radiated Power (EIRP) uplink limited tactical users. Furthermore, satellites with older bandwidth configurations (375 MHz) will be retrofitted with the Increased Bandwidth (IBW) modification (405 MHz) to make the frequency plan consistent with the B8-B14 spacecraft. SPECIFICATIONS Design Life 10 Years Size Main Stucture: 207 cm (L) x 193 cm (W) x 196 cm (D) With Solar Arrays Extended 11.4 M Liftoff Weight 2615 kg On-Orbit Weight 1170 kg Launch Vehicle Atlas II/Centaur/IABS/EELV Orbit Geosynchronous, Equitorial COMMUNICATIONS SUBSYSTEM Bandwidth (Production Satellites) Channel 1: 50 MHz Channel 2: 75 MHz Channel 3: 85 MHz Channel 4: 85 MHz Channel 5: 85 MHz Channel 6: 50 MHz RF Power Channel 1-6: 50 Watts Redundancy All Critical Paths Channel 1 & 2 Fully Redundant Channel 3-6 one for two redundancy Coverage Full Earth Narrow Coverage Rapid Selective Coverage Algorithm Receive Antennas Two Earth Coverage (EC) Horns One Steerable 61-Beam Nulling Lens (MBA) Transmit Antennas Two Earth Coverage (EC) Horns Two Steerable 19-Beam Wave Guide Lens (MBA) High Gain Parabolic Gimballed Dish EFFECTIVE ISOTROPIC RADIATED POWER (EIRP) Earth Coverage (MBA) 30 dBW Horn 32 dBW Narrow Coverage (MBA) 41 dBW Gimballed Dish 44 to 45 dBW Receiver Noise Figure (Low Noise Amp.) 3.8 dB Gain Control Range 39 dB