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Schriever Sentinel

Milstar gains new capability

U.S. Air Force graphic
Milstar is a joint service satellite communications system that provides secure, jam resistant, worldwide communications to meet essential wartime requirements for high priority military users. The multi-satellite constellation will link command authorities with a wide variety of resources, including ships, submarines, aircraft and ground stations.

By Staff Sgt. Robert Cloys

50th Space Wing Public Affairs

New software recently added to Milstar delivers additional functionality by using existing passive sensors on the system as a Wide Angle Sun Sensor, which provides extra protection to the satellite system in the event of gyro failure.

The new capability, also providing an extra layer of redundancy for end of life and safe state operations, was introduced to members of the 4th Space Operations Squadron here Aug. 14.

Milstar is a satellite constellation that provides the President, Secretary of Defense and the U.S. Armed Forces with assured, survivable satellite communications with a low probability of interception and detection. Designed to overcome enemy jamming and nuclear effects, Milstar is the most robust and reliable SATCOM system currently employed by the Department of Defense.

The objective of the Milstar program was to create a survivable, secure, nuclear-survivable, space-based communication system. Milstar was designed to perform all communication processing and network routing onboard, thus eliminating the need for vulnerable land-based relay stations and reducing the chances of communications being intercepted on the ground.

A key feature of the Milstar system is the use of interoperable terminals by the warfighters of the U.S. Armed Forces. Sea-based terminals can be used to upload data onto cruise missiles carried aboard submarines and guided missile destroyers in real time. Land-based terminals provide communications and data exchange for the mobile, ground-based warfighter.

With the growing demand for secure communications, developing new strategies for Milstar is essential.

“WASS is used as a redundancy system on Milstar,” said 1st Lt. Kyle Knight, 4 SOPS spacecraft engineer. “It allows for the satellite to acquire the sun via passive sensors on the spacecraft. WASS is a simple instrument that is always available. It also aids in end-of-life operations when a satellite needs to be put into a disposal orbit and the new software using the WASS assists with that.”

The new software provides a capability to perform an orbit-raising maneuver for disposing of spacecraft without the use of gyros for attitude control should there be a failure.

By essentially pointing a sensor on the wing of the spacecraft at the sun, it is able to detect the obvious source of power for its solar arrays and determine angular rates without the use of gyros.

“WASS is an additional way to point the spacecraft in a known direction, and is necessary for critical orbit raising burns,” said Bryan Essaf, Lockheed Martin technical advisor for attitude control. “Sunpointing has provided 4 SOPS with alternate strategies to deal with end of life scenarios as well, [while] providing a new mode that allows more time for troubleshooting and switching components. It is less dependent on traditional pointing hardware, and uses passive components with new software. As the constellation ages, space experts will continue to identify more proactive hardware strategies.”

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