TacSat-4

TacSat-4 is the third in a series of U.S. military experimental technology and communication satellites. The United States Naval Research Laboratory (NRL) is the program manager. 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 and the Operationally Responsive Space Office (ORS) funded the launch that will be performed by the Air Force's Space and Missile Systems Center (SMC).

The spacecraft was completed by the end of 2009, and was launched on 27 September 2011, at 14:49:00 UTC, on a Minotaur IV launch vehicle into a highly elliptical orbit (HEO).

Mission
TacSat-4 is equipped with a 3.6 m antenna operating 10 Ultra High Frequency (UHF) channels that can be used for any combination of communications, data ex-filtration or Blue Force Tracking (BFT). TacSat-4 will fly the highly elliptical, 4-hour, orbit (12,050 kilometers at peak) providing typical payload communication periods of two hours per orbit. TacSat-4's orbit also allows it to cover the high latitudes.

Part of its capability is rapid (within 24 hours) reallocation to different theaters worldwide, in support of unexpected operations. Command and control of TacSat-4 will be performed at the United States Naval Research Laboratory (NRL) Satellite Operations Center at Blossom Point, Maryland. Payload tasking will be performed via the SIPRNet based Virtual Mission Operations Center (VMOC).

Design
All TacSat satellites are designed to demonstrate the ability to provide real-time data collected from space to combatant commanders in the field.

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 University Applied Physics Laboratory, ATK Space, Ball Aerospace & Technologies, Boeing, Design Net Engineering, General Dynamics AIS, Microcosm, Sierra Nevada Corp., Massachusetts Institute of Technology, Lincoln Laboratory, Orbital Sciences Corporation, NRL, SMC, Space Systems/Loral, and Raytheon. Lithium-ion battery power provided by Quallion.