Building bandwidth in space

The military is developing the Transformational Satellite Communications program to give warfighters a new generation of global communications capabilities and bandwidth. The existing military satellite communications systems that it would complement are:

• UHF Follow-On. UFO provides protected communications for Navy ships and command-and-control networks to aircraft, ships and submarines. Later satellites carried the Global Broadcast Services Ka-band payload that provided each satellite with as much as 96 megabits/sec bandwidth. A final eleventh satellite was launched in 2003.
• Defense Satellite Communications Systems III. First launched in 1982, the DCSC fleet includes 14 satellites that each carries six super high-frequency transponders providing a total of 500 MHz of bandwidth. The final satellite was launched in 2003.
• Milstar. First launched in 1994, the Milstar constellation has five satellites that provide secure and jam-resistant communications with speeds as fast as 1.5 megabits/sec. The final satellite was launched in 2003.

The future military demand for satcom bandwidth also depends on the following programs.

• Wideband Global SATCOM. This program features a total of six satellites that will replace the DSCS fleet. They provide wideband communications through the X and Ka bands, and each satellite can provide as much as 3.6 gigabits/sec bandwidth, roughly 10 times more than a DSCS satellite. The first launch was in October 2007. Recent reports suggest the Air Force might buy additional satellites.
• Mobile Objective User System. The planned fleet of as many as six satellites will provide ultra-high-frequency narrow-band communications at about 40 megabits/sec that will replace the UFO system. Among other things, it will provide cell phone-like services to warfighters, in addition to beyond line-of-sight communications of 64 kilobits/sec. The first launch is scheduled for 2010, delayed from 2008.
• Advanced Extremely High Frequency. Slated to replace the Milstar fleet, current plans call for as many as four satellites, and each would have more than 10 times the bandwidth of Milstar satellites. The satellites would provide protected communications using the full range of low, medium and extended data rates — 75 bits/sec to 8.5 megabits/sec. The first launch is expected by 2010.

Source: Defense Department