Prime Minister Narendra Modi had previously called on the space agency to set up a space station by 2035 and send a man to the Moon by 2040.

While these missions may seem far off, an experiment crucial for sustained human spaceflight will be “launched in the next three to four months,” said Somanath during a lecture at Rashtrapati Bhavan Thursday.

The SPADEX experiment will demonstrate autonomous docking capability. Docking is a process where two spacecrafts are aligned in a precise orbit and joined together.

Explaining the mission, Somanath said: “Two satellites that are connected to each other will be launched, they will separate out, travel for a few kilometres, and then come back and connect.”

While India successfully developed the lander and rover on-board Chandrayaan-2 and Chandrayaan-3 missions after Russia backed out, Somanath said that for a sample-return mission “we need much more technology than what we have developed for the landing.”

He said work was on to develop technologies such as robotic arm to collect samples, mechanisms for docking in the Moon orbit and Earth orbit, transfer of samples, re-entry into the atmosphere without burning up — this will also be demonstrated by the Gaganyaan mission that will send astronauts to low Earth orbit and bring them back to Earth.

And while the ISRO recently demonstrated a trajectory to bring back a spacecraft from the Moon to Earth orbit using left-over fuel in the propulsion module, for a sample return mission the ascender module will have to collect the samples, come back to an orbit around the moon, and dock with another craft and transfer the sample, before it starts its journey back to Earth.

In Earth orbit, the spacecraft will have to dock with another module that will bring it to Earth. Just as with the Gaganyaan mission, the spacecraft with Moon samples will splashdown with the help of parachutes in the sea.

Somanath said that for sustained presence of Indians in space, ISRO is also working on developing an inflatable habitat module where the astronauts will be able to walk around and conduct experiments.

ISRO is also working on technologies such as satellites that will be able to re-fuel other satellites in space and ISRO Servicer Module that will be able to use robotic arms for maintenance of the modules and even replace modules when needed.

While the first module in 2028 can be launched with the existing rockets, he said, for building the entire space station a heavier launch vehicle will be needed. Somanath said ISRO was working on designing the Next Generation Launch Vehicle (NGVL) that will have a capacity to carry 16 to 25 T to low Earth orbit.

More importantly, ISRO is in discussion with NASA and the European Space Agency to build a common interface between the Indian space station and that of these countries. This interface will make joint work possible, said Somanath, indicating the possibility of collaborating with these countries for the space station. The current International Space Station has been built in collaboration with several countries and is likely to be de-orbited in 2030. The common interface will also allow the Indian module to go and dock with the ISS, he said.