India launched its first mission dedicated to testing spacecraft docking on December 30, 2024, placing two small satellites into low Earth orbit aboard an Indian-built rocket. The Indian Space Research Organisation said the Polar Satellite Launch Vehicle successfully delivered the Space Docking Experiment, known as SpaDeX, to its intended orbit.
The mission lifted off from the Satish Dhawan Space Centre in Andhra Pradesh at 4:30 p.m. GMT. ISRO Chairman S. Somanath announced after the launch that the PSLV-C60 rocket had placed the satellites in the correct orbit. Each spacecraft weighs about 220 kilograms.
SpaDeX was designed to demonstrate how two independently launched vehicles can approach one another, match their motion and connect in orbit. Mission controllers expected the first docking attempt could occur as early as January 7, provided the initial orbital operations and checks proceeded as planned. The launch itself established the starting conditions for that later test; it did not complete the docking maneuver.
Successful docking requires accurate navigation, communication and propulsion. The two vehicles must reduce their relative distance and speed through a controlled sequence while avoiding collision. Once connected, they need to behave as a combined spacecraft. Separating safely can also be part of the demonstration.
Only the United States, Russia and China had previously demonstrated uncrewed space docking. Completing SpaDeX would therefore make India the fourth country to independently achieve the capability. The technology has applications beyond a single experimental flight because it allows spacecraft or modules launched on different rockets to assemble and work together in orbit.
ISRO identified docking as important to several longer-term programs. These include returning samples from the Moon, sending Indian astronauts to the lunar surface and constructing and operating the proposed Bharatiya Antariksh Station. A station assembled from multiple modules would depend on reliable rendezvous and docking, while sample-return missions may require one spacecraft to transfer material to another before the trip home.
The experiment also supports missions too large or complex to be launched on a single rocket. Dividing hardware across multiple launches can expand what a space program can attempt, but only if the separate elements can meet and connect reliably after reaching orbit.
The December launch was therefore an early step rather than the conclusion of the mission. Engineers still had to guide the satellites through their planned orbital sequence and evaluate the docking system's performance. Data from that work would show whether the home-grown technology was ready to support India's more ambitious human-spaceflight, station and lunar plans.
