India: ISRO’s SpaDeX mission set to launch: A milestone in space docking technology

Dubai: The Indian Space Research Organisation (ISRO) is gearing up for the launch of its highly anticipated Space Docking Experiment (SpaDeX) mission on Monday (December 30, 2024) at 9:58pm IST (8.28pm UAE) from the Satish Dhawan Space Centre (SDSC) SHAR in Sriharikota.

Precision in Space: The SpaDeX mission’s small size and mass make it even more challenging, requiring extreme precision for the rendezvous and docking manoeuvres.

Unlike docking larger spacecraft, this mission demands fine-tuned control and navigation. ISRO notes that SpaDeX is a critical precursor for autonomous docking technologies that will be needed for future lunar missions without relying on GNSS support from Earth.

Advanced Navigation System: Both SpaDeX spacecraft are equipped with a differential GNSS-based Satellite Positioning System (SPS), which provides precise Position, Navigation, and Timing (PNT) solutions.

The mission also features a novel RODP processor in the SPS receiver, enabling the accurate determination of the relative position and velocity of the Chaser and Target.

What’s docking?

Docking is a process where two satellites are aligned and then joined in space — a necessity for missions that the space agency hoped to achieve in the future such as Chandrayaan-4 or setting up the Bharatiya Antariksh Station.

The Spadex mission will see two satellites — SDX01 or Chaser and SDX02 or Target — align in the same orbit, reduce distance between each other, join and transfer electrical power between them, and then separate.

This mission is a significant challenge, as the two satellites will be travelling at speeds up to ten times the velocity of a bullet, about 28,800 km/h — a difficult feat in the near vacuum of space.

To date, only Russia, the US, and China have mastered this technology.

The SpaDeX mission will see the launch of two small spacecraft weighing around 220kg each, carried by a PSLV rocket into 470 km above Earth. The primary goal is to demonstrate autonomous in-space docking.

Autonomously docking two fast-moving spacecraft in space is a complex task. As ISRO Chairman Dr. S. Somanath explained, the biggest challenge is ensuring that the two satellites maintain their orbits and do not collide during the docking process. Achieving this autonomous docking capability is a crucial step for India’s future space missions, such as Chandrayaan-4, building a space station, and sending an Indian astronaut to the moon.

The SpaDeX mission is an essential technology demonstration for future Indian space ambitions, including lunar missions, sample return from the moon, and the creation of the Bharatiya Antariksh Station (BAS).

In-space docking is critical for missions that involve multiple rocket launches, such as assembling large spacecraft or stations in orbit.