India launches its first on-orbit docking demonstration in 5th and final launch of 2024

The Indian Space Research Organization’s PSLV-C60 rocket lifts off from the Satish Dhawan Space Centre to begin the SpaDeX mission. Image: ISRO

India made another important leap forward in its space program with the launch of its first on-orbit docking demonstration mission on Friday, Dec. 30.

The Indian Space Research Organization (ISRO) launched a PSLV C60 rocket from the Satish Dhawan Space Centre at 10 p.m. IST (11:30 a.m. EST, 1630 UTC). The late night launch carried the primary payloads, named SDX01 and SDX02, which will carry out the mission.

The two spacecraft, roughly 220 kg (485 lbs) in mass, will attempt a docking at roughly 10 mm/s using a system similar in concept to the International Docking System Standard used onboard the International Space Station.



“Congratulations to the entire team of the PSLV project, who put the satellite in the right orbit,” said ISRO Chairman Sreedhara Somanath during comments made post-spacecraft separation on the ISRO broadcast. “Also, the SpaDeX team, who worked a very innovative, novel, cost-effective docking demonstration mission using two small satellite bus architecture.”

During his comments Somanath received word that the solar panels on the spacecraft had extended and were powering the twin spacecraft’s systems. He said the target date for completing the docking demonstration will be on Jan. 7.

Shri Sankaran, the director of U.R. Rao Satellite Centre, said SDX01 and SDX02 will orbit at a constant distance of 20 km (12.4 mi) apart. He said the craft will start moving into the docking process once they are correctly orientated to the Sun to receive sufficient power.

“At this point, again, we will initiate the drift of the two satellites so that the 20 km distance is progressively reduced to five km, 1.5 km,” Sankaran said. “After we reach 5 km, we are going to enable the inter-satellite RF link between these two satellites, so that the two satellites will talk to each other and exchange their own position, attitude, which will enable us to to evaluate the software logics, and also the several new sensors that have been developed by our laboratory for electro-optic systems.”

Some of those sensors include the Laser Range Finder, the Rendezvous Sensor and the Proximity & Docking Sensor. The two spacecraft also feature an optical camera system to allow for real time imaging of the event.

Launch Day is Here!

Tonight at precisely 10:00:15 PM, PSLV-C60 with SpaDeX and innovative payloads are set for liftoff.

SpaDeX (Space Docking Experiment) is a pioneering mission to establish India’s capability in orbital docking, a key technology for future human… pic.twitter.com/147ywcLP0f

— ISRO (@isro) December 30, 2024

Sankaran said once the satellites get within three meters of each other, a final algorithm will kick in. Once contact is made, the chase satellite (SDX01) will retract its previously extended capture ring pull the target satellites (SDX02) towards it to become one unit.

“After this, the combined two satellite composite will be controlled by the control system of one of the satellites,” Sankaran said. “This is important new equipment, enabling for the future where we go and dock it to the International Space Station, our Bharatiya Antariksha Station or any other satellite.”

Docking will also play a key role the next time India sends a mission to the Moon. The Charndrayaan-4 mission will need accurate docking in order to support the plans for lunar sample return.

The Ascender Module and Descender Module would launch as one stack on one LVM3 rocket and the Re-entry Module, Transfer Module and Propulsion Module would launch as a separate stack on a separate rocket. ISRO plans to launch the mission to the Moon in 2028.