Sensors for On-Orbit Docking

Docking two spacecraft on orbit is hard, but there are space sensors that make the job easier.

The first time I saw how astronauts docked the Space Shuttle to the International Space Station, I was taken aback. They didn’t use any fancy space sensors. They had a camera looking at a visual target on the docking port, and they navigated by eye. Was that really the best they could do? Russian Kurs, one of a number of space sensors for on-orbit docking, guides a Progress ship into dock

It turns out that doing automatic, robotic docking is hard. The USSR’s used the Kurs radar system to dock automatically, which works well as long as no trash bags get in the way. The US tested a bunch of space sensors with mixed results, including a couple of systems I got to help design and build. In both DARPA’s Orbital Express demonstration and Japan’s ETS-VII experiment, the target satellite got lost and had to be recovered. NASA’s first test of the AVGS sensor led to one satellite ramming another. The history of automatic on-orbit docking is filled with near-misses and almost-disasters.

In my presentation on the subject, I talk about what it takes to build a space sensor for docking and go through the history of various attempts at docking automatically. Here’s the version of it I gave at a NASA colloquium. If you’d like a briefer introduction to the topic, I discussed the topic on the Weekly Space Hangout with Fraser Cain.