Results of the Compact Ocean Wind Vector Radiometer Demonstration Mission: A Small-Sat Conical Microwave Imager

The advent of small satellites and miniaturized instrument technology enables a new paradigm for observation from Low Earth Orbit (LEO). Passive microwave radiometer systems, such as SSM/I, AMSR-E, AMSU, ATMS, WindSat and GMI, have been providing important Earth observations for over 40 years, including but not limited to surface wind vector, atmospheric and surface temperature, water vapor, clouds, precipitation, snow and sea ice. There are many recent examples of successful CubeSat based mm-wave microwave sounders, such as TEMPEST-D, TEMPEST-H8 and TROPICS. The Compact Ocean Wind Vector Radiometer (COWVR) is the first demonstration of a low-cost, small-sat compatible conical microwave imager for atmospheric and surface observation, including ocean vector winds.

COWVR has been operating on the International Space Station (ISS) since January 2022 along with the TEMPEST-H8 microwave sounder. COWVR provides measurements of ocean vector winds, precipitable water vapor, clouds and precipitation while TEMPEST-H8 provides retrievals of vertical water vapor profiles and ice cloud properties, including convective intensity. We present the in-flight performance from the first 2 years of operation of COWVR and TEMPEST-H8, focusing on the wind vector, water vapor, precipitation and cloud water products, demonstrating a compact sensor can perform as well as current generation operational sensors.

COWVR is demonstrated to perform as well as the legacy WindSat microwave imager with an additional advantage of two-look (forward and aft) retrievals, reducing ambiguous solutions and improving overall performance. We compare the COWVR wind vector products to those produced from the operational ASCAT scatterometer system, showing nearly equivalent performance. The COWVR data products are available with 1-2 hour latency and are in operational use by the Naval Research Laboratory. The brightness temperature and retrieval products will be distributed publicly via the NASA PO.DAAC beginning in September 2023.

COWVR has demonstrated a new sensor architecture suitable for deployment in a small-satellite constellation. We will describe a follow-on imager/sounder concept derived from the COWVR architecture that is a software defined digital system operating over a wide spectrum enabling new measurements of air-sea heat and moisture exchange as well as the traditional product suite derived microwave imagers and sounders.