NRL Positions Unique Elliptic-Orbit TacSat-4 Satellite for Launch


Naval Research Laboratory spacecraft personnel make final preparations to ready the TacSat-4 spacecraft for a May 2011 launch. Transported March 1, to the Kodiak Alaska airport via an Air Force C-17 and trucked to the Alaska Aerospace Kodiak Launch Complex, the TacSat-4 satellite will be launched aboard an Orbital Sciences Minotaur-IV launch vehicle into a highly elliptical orbit (HEO) with an apogee of 12,050 kilometers.

TacSat-4 is a Navy-led joint mission managed by the NRL Naval Center for Space Technology. The mission of TacSat-4 is to experiment with new satellite communications (SATCOM) techniques, augment current SATCOM capabilities, and advance the development of Operationally Responsive Space (ORS) systems for improved responsiveness of space capabilities.

TacSat-4 augments current SATCOM by providing communications-on-the-move (COTM) for existing radios without requiring antenna pointing and providing 10 Ultra High Frequency (UHF) channels that can be used for any combination of communications, data ex-filtration, or Blue Force Tracking -- a system that provides military commanders and forces with location information about friendly military forces.

TacSat-4 provides flexible up and down channel assignments, which increases the ability to operate in busy, and sometimes restrictive, UHF environments. The unique orbit of TacSat-4 also augments geosynchronous SATCOM by providing near global, but not continuous, coverage to include the high latitudes.

"The ability to provide communications on the move without having to stop and point a SATCOM antenna was the most important user requirement and one which drove the design of the system," said Mike Hurley, section head, NRL Spacecraft Development.

The NRL Blossom Point Ground Station provides the command and control for TacSat-4 and maintains its user Virtual Mission Operations Center (VMOC) tasking system, allowing dynamic reallocation to different theaters worldwide and enabling rapid SATCOM augmentation when unexpected operations or natural events occur.

The Office of Naval Research (ONR) sponsored the development of the payload and funded the first year of operations. The Office of the Director of Defense Research and Engineering (DDR&E) funded the standardized spacecraft bus. The Operationally Responsive Space (ORS) Office funded the launch that will be performed by the Air Force Space and Missile Systems Center (SMC).

The spacecraft bus was built by NRL and Johns Hopkins University Applied Physics Laboratory (APL) to mature ORS bus standards developed by an Integrated (government and industry) System Engineering Team, the "ISET Team," with active representation from AeroAstro, Air Force Research Laboratory, Johns Hopkins Laboratory APL, ATK Space, Ball Aerospace and Technologies, Boeing, Design Net Engineering, General Dynamics AIS, Microcosm, Microsat Systems Inc., Massachusetts Institute of Technology Lincoln Laboratory, Orbital Sciences, NRL, SMC, Space System Loral, and Raytheon.

The Naval Research Laboratory is the Department of the Navy's corporate laboratory. NRL conducts a broad program of scientific research, technology, and advanced development. The Laboratory, with a total complement of nearly 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif.

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