The Indian Space Research Organisation (ISRO) achieved another milestone with the successful launch of the Space Docking Experiment (SpaDeX) mission on Monday, December 30, 2024. This mission marks a significant step in India’s space exploration capabilities, focusing on advanced technologies essential for spacecraft rendezvous and docking.
The mission was carried out using the PSLV C60 rocket, which lifted off from the first launchpad at the Satish Dhawan Space Centre in Sriharikota at 10 p.m. The rocket carried two small satellites, SDX01 (Chaser) and SDX02 (Target), along with 24 additional payloads. Approximately 15 minutes after the launch, the satellites, each weighing about 220 kg, were placed into a 475-km circular orbit, as planned.
“The rocket has placed the satellites in the right orbit, which is a 475-km circular orbit. The spacecraft’s solar panels have been deployed successfully. The two SpaDeX satellites have moved one behind another. Over time, this distance will increase by 20 km, and the rendezvous and docking process will begin. The docking process can happen in another week; the nominal time will be approximately January 7,” stated ISRO Chairman S. Somanath.
Aiming for Advanced Space Technologies
The SpaDeX mission is designed to demonstrate technologies for spacecraft rendezvous, docking, and undocking. These capabilities are critical for future space missions, including sending an Indian astronaut to the Moon, conducting sample return missions, and establishing the Indian Space Station. So far, only a select group of spacefaring nations have mastered such advanced techniques.
The mission’s objectives rely heavily on the precision of the PSLV C60 launch vehicle. According to ISRO, the demonstrated accuracy of the rocket will enable the Target and Chaser spacecraft to maintain a small relative velocity during their separation from the launch vehicle. This precise control is vital for the success of the docking process.
Step-by-Step Docking Procedure
ISRO explained that the Target spacecraft would use its propulsion system to gradually create a separation of 10-20 km from the Chaser spacecraft within the first day. “This incremental velocity will allow the Target spacecraft to build a 10-20 km inter-satellite separation with respect to the Chaser within a day. At this point, the relative velocity between the Target will be compensated using the propulsion system of the Target spacecraft,” ISRO clarified.
Once this drift arrest maneuver is complete, the Target and Chaser will share the same orbit, moving at identical velocities but separated by about 20 km. This stage is referred to as “Far Rendezvous.”
The Chaser will then approach the Target in a phased manner, gradually reducing the inter-satellite distance to 5 km, 1.5 km, 500 m, 225 m, 15 m, and finally 3 m. Ultimately, this sequence will result in the docking of the two spacecraft. “With a similar strategy of introducing and then compensating for a small relative velocity between the two spacecraft, the Chaser will approach the Target with progressively reduced inter-satellite distances, ultimately leading to the docking of the two spacecraft,” ISRO added.
Timeline for Docking
The docking operation is expected to occur between January 7 and 10, according to U.R. Rao Satellite Centre Director M. Sankaran. This timeline aligns with the mission’s nominal schedule, showcasing ISRO’s commitment to precision and technological excellence.
Additional Payloads Onboard
In addition to the SpaDeX mission, the PSLV C60 carried 24 PS4-Orbital Experiment Module (POEM-4) payloads. These payloads are part of ISRO’s broader objectives to advance space science and technology through innovative experiments.
The SpaDeX mission represents a leap forward for ISRO, placing India among the elite nations capable of performing complex spacecraft docking maneuvers. By mastering these advanced technologies, ISRO is paving the way for ambitious missions that will strengthen India’s presence in space exploration.