Global precipitation measuring satellite

GPM, the successor to TRMM, is up.

Japan Launches Next-Generation NASA Satellite to Track Rain & Snow | Space.com

A few things about it. TRMM functioned well beyond its design life. I do not know how they do that. One starts out with only so much 'station-keeping' fuel and refills are not possible.

The stated cost of about 1 Billion helps us get a handle on the cost of these things. I still don't know about lifetime management costs for these larger satellites. If one is concerned about the cost of earth system science research here is one of the biggies.

Link states that GPM will provide complete coverage every 3 hours. Those familiar with orbital mechanics know that this is not actually possible. Here is how it's done: Global cloud-top temperatures are updated at that rate, by other passive microwave birds in higher orbits. There are several of those. When the views of those and the GPM coincide, the local relationships between cloud-top temperatures are found. Then local rain rates are 'infilled' when the GPM is looking somewhere else.

GPM adds more microwave capability to measure snow and lower rain rates than TRMM. How well those can be related to cloud-top temperatures remains to be demonstrated I suppose. This is not something that can be tested in a lab.

After GPM checkouts and a period of intercalibration, TRMM will be dumped into the Pacific Ocean. Having been one of the more useful tools, I'd say.