India’s Space Research Organisation (ISRO) has successfully docked a pair of satellites, making the nation the fourth to achieve the feat.
The Space Docking Experiment (SpaDeX) commenced on December 30, 2024, when India launched a pair of satellites equipped with docking equipment. The mission plan called for the two to be separated after launch, with one designated as the target and the other as the chaser
Once re-united, the two sats transfer power and enter a mode under which they could be controlled as a single entity. India plans to later split the sats and operate them independently, so they can each deploy their payloads.
Between January 7th and 15th ISRO made three attempts to dock the sats. The first was postponed after ground control decided it needed to revise abort procedures. The second abandoned after one of the sats was moved but drifted further than anticipated.
The third attempt saw the orbiting machines close to within 15 meters, and then to three meters. Those two steps are part of the docking procedure but ISRO decided to back off and check the quality of sensor data. The sats were sent further apart again.
Thursday’s fourth attempt succeeded
“Manoeuvre from 15m to 3m hold point completed. Docking initiated with precision, leading to successful spacecraft capture. Retraction completed smoothly, followed by rigidisation for stability. Docking successfully completed,” states an ISRO Xeet posted at 04:34 UTC on January 16th.
Only the USA, China, and Russia had achieved this before. The three nations are also the only ones to have launched crewed missions into space. India aims to join them in 2026 a couple of years with the first of eight planned “Gaganyaan” missions, and follow up with a lunar lander, a space station, and a Venus orbiter.
SpaDeX tested tech needed for those missions.
Two days before India’s hooked up in space, two European Space Agency (ESA) craft broke up – by design. The pair were the Proba-3 craft that are designed to fly in formation so that one – the “Occulter” – flies in front of the “Coronagraph” to block its view of the sun.
Once Sol’s full glare is obscured, Coronagraph will be able to observe the star’s corona – its outermost layer – which is thought to offer insights into the Sun’s behavior. The corona is briefly visible during solar eclipses. Proba-3 aims to offer the chance for more frequent and extensive observations.
To do so, the two sats will need to fly in tight formation. Achieving that is the mission’s main objective.
The two Proba-3 sats have been joined since they were launched last December. The ESA on Wednesday explained it will now let them drift until they are around 50km apart, before positioning them just 150m apart.
The two “will need to maintain their relative position down to a single millimetre, for up to six hours at a time” according to the ESA announcement. If all goes well, that will be possible by March, when corona observations will commence. ®
