Science By Paul Voosen May. 2, 2019
The International Space Station (ISS) has never been known as a hotbed of science, even though the United States and partner nations spent more than $100 billion to build it. Inside its cramped bays, astronauts study the biological effects of microgravity, and a few astrophysical experiments are mounted to its exterior. But 2 decades after it started to take shape, the ISS has finally found a scientific calling: looking down at its home planet.
The ISS is now home to five instruments that observe Earth, with two more set to join this year. One, NASA's Orbiting Carbon Observatory 3 (OCO-3), was scheduled for launch this week from Cape Canaveral, Florida, aboard a routine resupply mission. Its launch marks a political victory: President Donald Trump has proposed canceling OCO-3 several times, only to be rebuffed each time by Congress. It also marks a victory of expedience over perfection.
The ISS is not the ideal platform for OCO-3, which was built to fly on a stand-alone satellite. In fact, "It's probably not the perfect platform for almost anything," says Michael Freilich, who led NASA's earth science division in Washington, D.C. for 12 years until his retirement in February. "It's big. It flexes. It travels around in a cloud of contaminants." And, most important, its orbit misses the poles and revisits sites at a different time each day. But compared with launching a satellite, mounting the instrument on the ISS is vastly cheaper: At $110 million, OCO-3 costs a quarter as much as OCO-2, which launched as a stand-alone mission in 2014.
More:
https://www.sciencemag.org/news/2019/05/international-space-station-has-found-its-scientific-calling
