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The DMSP Space Segment

The Space Segment consists of the DMSP spacecraft, the launch vehicle, and ground and factory support for the launch.

The spacecraft is placed into a near-circular, Sun-synchronous polar orbit at a nominal altitude of 450 nautical miles.

The spacecraft is 3-axis stabilized and Earth oriented. Sensing instruments are maintained in a continuous orientation toward Earth or space. The solar array rotates about the pitch axis to provide single-axis Sun orientation.

Cutaway, underside view of 5D-3 spacecraft
Figure: Cutaway, underside view of 5D-3 spacecraft.

In addition to the sensor suite, the spacecraft is divided into eight major subsystems. However, for this document, we will only address the major on-orbit functions, which are:

The spacecraft collects power by way of a deployable solar array. Two batteries onboard store excess energy for operation during peak periods and for periods during which the spacecraft is in darkness.

Receipt of commands, downlink telemetry, and mission sensor data is accomplished via the Communications Subsystem.

The Equipment Status Telemetry Subsystem provides health and welfare status, as well as command verification reporting to the ground system.

Using a combination of stellar reference and inertial measurements made by gyros, a Sun-sensor unit, and an Earth-sensing Assembly, attitude errors and satellite position are determined. Once determined, attitude corrections are made by Reaction Wheel Assemblies.

The Command and Control Subsystem accepts real-time and stored commands for routing and processing. These commands may perform stationkeeping for the spacecraft or direct data collection by the sensor suite.

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Designed and Developed by

The Aerospace Corp.

John Bohlson, Leonard Daly, and Charles Simmons
The Aerospace Corporation
Last modified on July 03, 1997

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DMSP WebMaster - James Dixon