What is the rotating gold object on the outside of ISS? It is sometimes in view on the Live_ISS_Stream SD video feed: https://video.ibm.com/channel/live-iss-stream# A Google search gives no current results.
The spinny thing is the 75cm reflector of the COWVR (Compact Ocean Wind Vector Radiometer).
The whole package is known as STP-H8 and is composed of three instruments: COWVR, TEMPEST, and GARI-2 (GAGG Radiation Instrument-2):
The instrument is in its folded position before being deployed after installation on the Exposed Facility.
Launched on SpaceX CRS-24, 21 December 2021
The STP-H8 (Space Test Program - Houston 8) is a combo of experiments to be hosted on the International Space Station (ISS).
STP-H8 will carry the COWVR (Compact Ocean Wind Vector Radiometer) as a replacement to the cancelled free-flying ORS 6 (COWVR) satellite.
The COWVR payload being developed by the Jet Propulsion Lab (JPL) for the Space and Missile Systems Center (SMC) Weather Directorate which would address the need for ocean surface vector wind data, which currently comes from the U.S. Naval Research Laboratory’s Windsat payload on the Coriolis (P98-2) satellite, which was launched in 2003 and is well beyond its expected design life.
NASA’s Jet Propulsion Laboratory built COWVR’s sensor, which improves upon the design of the Advanced Microwave Radiometer flown on the U.S./European Jason-2 and Jason-3 satellites.
The main purpose of the Compact Ocean Wind Vector Radiometer (COWVR) instrument is to measure the direction and speed of winds at the ocean surface.
The other part to it is the Temporal Experiment for Storms and Tropical Systems (TEMPEST) looks at atmospheric humidity, and is about the size of a breakfast cereal box.
Designed and built at NASA’s Jet Propulsion Laboratory in Southern California, the two instruments are technology demonstrations.
The space station orbit will give COWVR a view of the ocean surface at different times of day on each orbit, compared with a Sun-synchronous orbit that carries a satellite over any part of globe at the same time each day. Over time, this will aid understanding of how ocean waves develop and change throughout the day.
COWVR is a successor to the WindSat which was a polarimetric microwave radiometer developed by the US Navy and the National Polar-orbiting Operational Enviromental Satellite System for measuring ocean surface wind speed and direction.
WindSat was the primary payload on the Department of Defense Coriolis satellite, which was launched in 2003, to a 840-km circular sun-synchronous orbit. The reflector, along with the majority of the sensor hardware, rotates at a nominal rate of 31.6 r/min.
Installed on January 7th 2022:
STP-H8 was the first of the payloads to be removed from the SpaceX Dragon trunk by NASA’s robotics operators on Jan. 7 and installed on its external hosting site, the Japanese Experiment Module.
“Both payloads were fully deployed with all science experiments functional within just a few hours of the robotic transfers.”
STP-H8 and STP-H7 mounted inside the SpaceX CRS-24 Cargo Dragon.
COWVR is evidently a replacement for the US Department of Defense WindSat "to measure the direction and speed of winds at the ocean surface."
Shannon Brown, a JPL engineer, had been working on a microwave radiometer for the oceanographic mission Jason-3, developed by NASA, the National Oceanic and Atmospheric Administration, and European partners to measure sea surface height. Brown recognized that the Jason-3 instrument’s design advances could be repurposed to meet the needs of weather forecasters. “We put a concept together that used most of the Jason-3 hardware designs, and we found it could measure wind speed and direction at a much lower cost than what the Air Force was building,” he said.
The novel aspect of COWVR is its simplified design. The WindSat radiometer rotates about 30 times a minute as it gathers data. The engineering challenge of developing and powering up parts that can rotate many millions of times in space has proven to be one of the most expensive and demanding aspects of radiometer development.
COWVR reduces the number of moving parts, replacing hardware with algorithms newly developed for the instrument by Brown and his colleagues. The algorithms tease the desired signals of wind speed and direction out of the raw data stream. Parts that still must rotate are now housed on a turntable so they don’t need to be powered individually. The streamlined instrument weighs only 130 pounds (58.7 kg) and uses 47 watts of power to operate – about as much as a bedside lamp – where WindSat weighs 990 pounds (450 kg) and uses 350 watts.
The ESA eoPortal linked above is the best resource I've found so far, and the blockquote and quote in the preceding paragraph are both from there. Here's a smattering of other links:
The Aegis Aerospace Tweet that led me to STP-H8 while I was searching for JEM EF payloads and lamenting that there's wasn't a single obvious resource for current or historical configurations thereof. The module with its deployed gold antenna is featured in a photo in said tweet, which I'll reproduce here.
An Odyssey Space Research blog post on STP-H8 and H7 being launched on SpaceX CRS-24