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"They were thrown into space together but at the time of separation, they were placed with different velocity to allow them to build a distance of 10-20km between them," Mila Mitra, a former Nasa scientist and co-founder of Delhi-based space education company Stem and Space, told the BBC.

This, Ms Mitra, says is to demonstrate that a spacecraft can be sent to service another in space.

Ms Mitra says the mission will also test India's capabilities for inter-satellite communication as during the docking and undocking, the spacecraft will have to communicate with the Earth station and also with each other so that they know each other's position and velocity.

The second experiment involves the robotic arm which, Ms Mitra says, is among the rocket's most important payloads.

Ms Mitra says this arm will play "a crucial role during the building of the space station as it could be used to capture and put things in place".