With its growing space program, India will attempt a new feat tonight: docking two satellites together in orbit for the first time. This kind of maneuver requires extremely precise movements and planning, and in the long term, will help India’s ambition to send increasingly sophisticated missions to the moon. The Indian space agency, the ISRO, will livestream the event tonight so you can watch at home.
Coverage begins at 9:15 p.m. ET tonight, Wednesday, January 8, and you can watch on YouTube or using the video embedded below:
The docking is part of an experiment called SpaDeX, or Space Docking Experiment, and involves a pair of satellites that were launched on December 30, 2024. Both spacecraft, which are just 485 pounds each, were launched into an orbit 290 miles above the Earth and will attempt to dock together using automated docking technology.
“SpaDeX, because of its small size and mass, is even more challenging due to the finer precision required for the rendezvous and docking maneuvers compared to docking two large spacecraft,” ISRO wrote. “This mission will be a forerunner for autonomous docking needed for future lunar missions like Chandrayaan-4 without the support of [global navigation satellite system] from Earth.”
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India wants to follow up its successful Chandrayaan-3 mission to the moon with a more complex mission, Chandrayaan-4, which will return a lunar sample to Earth. This will require spacecraft to dock in orbit, so the SpaDeX mission is a test of this capability. In the longer term, India also has plans to develop a space station, for which in-orbit docking technology is essential.
It is still relatively rare for two satellites to dock due to the challenges from their smaller size and less sophisticated controls compared to larger spacecraft. The two satellites involved in the docking tonight, named Target and Chaser, will have to reduce their relative velocities to just 0.2 mph while both are traveling at speeds of 18,000 mph.
Once the two are docked, they will fasten together and test out the sharing of electrical power before undocking and separating. The dramatic maneuver won’t be the end of their lives, however, as both will continue operating their instruments, including a high-resolution camera and a radiation monitor, for up to two years, collecting data on Earth observation and the space environment.