New Communication Satellite Touted as a Life-Saver

4/13/2011
By Stew Magnuson
COLORADO SPRINGS, Colo. — Lives have been lost when U.S. troops have climbed to higher ground looking to establish communications links with satellites.
Lt. Michael Murphy, a Navy SEAL, was posthumously awarded the Medal of Honor for leaving his position during a battle in Afghanistan in 2005. He successfully put the equipment in place that allowed his fellow SEALs to link to a communications satellite in geosynchronous orbit some 25,000 miles above the Earth, but was shot and killed while doing so.
A new satellite awaiting launch at Kodiak, Alaska, will allow units to communicate with higher headquarters from deep canyons, without having to expose themselves to enemy fire.
TACSAT-4, aNavy-led program, will carry a UHF communications payload that will allow forces to directly connect to secure communication satellites via handheld radios. The Defense Department's Operationally Responsive Space (ORS) office is funding the launch.
The catch is that for now, it will only work for six to seven hours per day, said Peter Wegner, director of the ORS office. TACSAT-4 will travel in an unusual elliptical orbit over the polar ice caps that will give it long dwell times over an area of operation. Most military communication satellites are in geosynchronous orbit, and are in fixed positions. They are available 24 hours a day, but those seeking to link to them must use powerful boosters and have a direct line of sight to their transponders.
In Afghanistan, infamous for its deep valleys, that often means climbing out of gullies to place antennas in ideal spots. TACSAT-4 will quickly swoop as close as 400 kilometers to Earth, then on the opposite side of the elliptical orbit, climb to about 12,000 kilometers and slow down enough at its peak to give troops about two hours of connection time. It can make about three to four passes per day, Wegner said at the Space Symposium here.
The ORS office worked with the Naval Research Laboratory to build the payload, which can work with analog radios or new software defined radios, Wegner said.
The original May 5 launch date has slipped because of thefailure of a Taurus rocketduring a NASA mission last month. TACSAT-4 will go aboard a Minotaur rocket, but since both launch vehicles are built by Orbital Sciences, and have many common parts, the mission is on hold until the end of the accident investigation.
Officials hope that TACSAT-4 will prove the utility of a UHF payload in low earth orbit. After the results of the mission are studied, then the Air Force may consider a fleet of three or four such spacecraft that would collectively provide coverage of one area around the clock, Wegner said.
For now, "most commanders will be happy to have a few hours a day of this capability available," Wegner said.

Topics: Space

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