Small Air Force microwave sensor to fly on space station

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The U.S. Air Force plans to test the performance of a small microwave sensor developed by NASA’s Jet Propulsion Laboratory on the International Space Station in 2021.

The conical microwave sensor, called Compact Ocean Wind Vector Radiometer (COWVR), is designed to reduce the cost, mass and power consumption of instruments capable of making global observations of wind, temperature and precipitation near Earth’s surface.

What’s unique about COWVR is that its aluminum reflector rotates while its feed horn and other electronics remain stationary, making it far smaller, less power hungry and easier to accommodate on a spacecraft than sensors that spin the entire radiometer, said Shannon Brown, COWVR principal investigator in JPL’s Microwave Instrument Science Group.

If the on-orbit demonstration is successful, “we could see a shift in the way we design and build conical microwave sensors,” Brown said. For example, several small sensors could be deployed for the cost of a single large sensor, reducing revisit time and improving weather forecast models, Brown said.

In 2016, the Air Force announced plans to send COWVR into a 600-kilometer sun-synchronous orbit on a 300-kilogram satellite as part of a mission dubbed Operationally Responsive Space-6. Last year, after JPL delivered the sensor to the Air Force Space Rapid Capabilities Office, which was previously known as the Operationally Responsive Space Office, the Air Force canceled launch plans to launch ORS-6 due to problems with the satellite bus.

Now, the Air Force plans to send COWVR to the space station in 2021 for one to three years as part of a group of instruments and experiments known as Space Test ProgramHouston 8. The Defense Department has long coordinated with NASA to fly instruments and experiments on ISS or other crewed spacecraft through its Space Test Program office in Houston.

“The purpose of the COWVR technology demonstration is to mature the new microwave design and prove its functionality on-orbit,” the Air Force Space and Missile Systems Center (SMC) said in written responses to questions. “A successful demonstration could reduce overall development and launch costs for future microwave programs, which track and forecast hurricanes and typhoons as well as deliver sea surface wind direction and speed data.”

Last year, the Air Force began reorganizing SMC in an effort to speed up development and production of space systems. The reorganized agency is known as SMC 2.0.

Air Force and NASA cooperation on the COWVR program “is a prime example of the Air Force SMC 2.0 focus to enable potential space acquisition using interagency partnerships, where it makes sense,” SMC said.

COWVR is designed to measure ocean surface vector winds as well as the WindSat microwave radiometer launched in 2003 on the Naval Research Laboratory’s Coriolis satellite except in heavy rain cells. A future sensor could add lower-frequency channels to obtain measurements through rain cells, Brown said.

Ocean wind monitoring is a high priority for the Defense Department. While the Air Force conducts the COWVR technology demonstration on the space station, Ball Aerospace & Technologies Corp. is building Weather System Follow-on Microwave, an operational satellite equipped with passive microwave imaging radiometers to monitor ocean winds and cyclone intensity as well as an energetic charged particle sensor.