Photos by the INDIAN SPACE RESEARCH ORGANISATION
India has climbed further in its pursuit of space capabilities with the successful docking of two small, unmanned spacecraft in low Earth orbit. India is just the fourth nation to accomplish the feat.
The spacecraft, each the size of a large refrigerator, linked up on January 16, 2025, after a week’s delay — 17 days after they were launched from Satish Dhawan Space Centre aboard an Indian-made Polar Satellite Launch Vehicle (PSLV). Called Target and Chaser, the spacecraft comprise the Indian Space Research Organisation (ISRO) mission known as Space Docking Experiment (SpaDex).
SpaDex was among 24 payloads aboard the PSLV-C59 rocket, triple the capacity of earlier Indian platforms and an additional milestone for ISRO. The other payloads are designed to conduct science and engineering experiments.
Docking capabilities will help advance India’s space ambitions, including moon landings, the return of samples from the moon, and the construction and occupation of the Bharatiya Antariksh Station in low Earth orbit planned for 2028. “In-space docking technology is essential when multiple rocket launches are required to achieve common mission objectives,” ISRO said in a SpaDex web profile. “Through this mission, India is marching towards becoming the fourth country in the world to have space docking technology.”
The other countries are China, Russia and the United States.
SpaDex was designed and developed at ISRO’s UR Rao Satellite Centre in Bengaluru. Among the indigenous technologies created for the mission are the docking mechanism, rendezvous and docking sensors, power transfer, autonomous rendezvous and docking, inter-satellite communication link, and a processor to determine the relative position and velocity of each spacecraft. Their approach velocity was a snail’s pace of 10 millimeters per second.
Because of its small size and mass, the SpaDex mission proved especially challenging, ISRO said, with the finer precision required for rendezvous and docking maneuvers compared to two spacecraft as large as, for example, the International Space Station and a Dragon crew capsule.