NASA’s next Mars lander will have some company for the long trip: twin communication satellites the size of a briefcase. As the lander plunges through the Martian atmosphere, the satellites will relay its signals back to Earth. The two spacecraft, known as Marco, are only a test. There’s already a big satellite in Mars orbit that’ll serve as a relay station. But if Marco works, many more small satellites could follow. In fact, NASA, universities, and private companies are developing smaller and smaller spacecraft to do a variety of missions. Some craft aren’t much bigger than baseballs, and weigh only a few pounds. Collectively, they’re known as nanosats, and a couple of hundred have been launched. They often fly as tag-alongs to larger spacecraft. There’s usually an extra bit of room for small payloads, which can serve as ballast to keep the rocket balanced during launch. Nanosats cost a lot less than conventional satellites, and they take much less time to develop. That opens up spac
