New satellite could revolutionize battlefield communications

The Naval Research Laboratory on Tuesday launched an experimental, $75 million satellite that U.S. ground forces can use for on-the-move communications with standard military handheld or back radios.

The Tactical Satellite-4 (TacSat-4) will zoom around Earth in an elliptical orbit at altitudes ranging from 435 miles to 7,470 miles, keeping the spacecraft far closer than the 22,000-mile orbit of geostationary communications satellites, according to the Operationally Responsive Space Office at Kirtland Air Force Base, N.M., which funded the launch and first six months of use.

Michael Hurley, head of spacecraft development for the Naval Research Lab, said in an email from the TacSat-4 launch site in Kodiak, Alaska, the low orbits will allow ground forces for the first time to communicate with a military satellite using omnidirectional antennas on their radios while on the move, rather than stopping to set up a satellite antenna.

TacSat-4, Hurley said, will support troops in Afghanistan equipped with An/PRC-148 and AN-PRC-152 handheld radios, manufactured by Thales and Harris respectively, and the Harris AN/PRC-117 backpack radio, as well as the AN/PSC-5 portable satellite terminal from Raytheon fielded to Special Forces units. Hurley said all these radios communicate with TacSat-4 in one of 10 channels in the 240-318 MHz band, which is also used by the Defense Department's geostationary ultra-high frequency satellite constellation.

The experimental satellite serves as a "bent-pipe" to passively relay signals from one of these radios to another, Hurley said. To connect to Defense networks, most users would have to be within about 1,000 miles of a TacSat-4-specific ground terminal -- either the In-Theater Ground Terminal, currently located at Blossom Point, Md., or five portable ground terminals, positioned throughout the United States during the first year of tests.

Army and Marine Corps ground forces deployed in Afghanistan "strongly support" TacSat-4, which will fill in areas that currently lack satellite coverage, Hurley said. But, due to its elliptical orbit, the satellite will not provide 24-hour-a-day coverage. Kabul will get up to four passes a day, ranging from 50 minutes to 2 1/2 hours, he said.

It would take between three and four spacecraft to provide 24-7 coverage, depending on the locations of interest, and no follow-on procurement for TacSat-4 has been funded, Hurley said.

TacSat-4 has a lifespan of about three years, he said, and the Operationally Responsive Space Office and the Defense satellite acquisition community will evaluate the performance and user feedback from TacSat-4 to determine if follow-on birds will be procured.

Defense established the Operationally Responsive Space Office in 2007 and previously backed development of an imaging and signals intelligence satellites. Peter Wegner, director of the Office, said TacSat-4 will "open some eyes as to what small satellites can do in providing big time capabilities to the warfighter . . . Being able to communicate on the move with a handheld, legacy military radio is huge. This capability does not currently exist."