Syllabus: 

GS3: Awareness in the fields of IT, Space, Computers, Robotics, Nano-technology, Bio-technology and issues relating to Intellectual Property Rights.

Context: 

Recently, Scientists at the Indian Space Research Organisation (ISRO) have been drawing up plans for a second SpaDeX mission.

More on the News

• After successfully bringing together two satellites in space, scientists at the Indian Space Research Organisation (ISRO) are drawing up plans for a second SpaDeX mission 

SpaDeX Mission 

In the first SpaDeX mission, two 220-kg satellites were launched into a 470-km circular orbit. With a small relative velocity introduced between them, the satellites were allowed to drift apart before being progressively brought closer. 

The experiment also demonstrated power sharing between the satellites and their ability to receive commands as a single composite unit.

With this, India became only the fourth country, after the US, Russia, and China, to demonstrate in-space docking capabilities. However, the feat was carried out in a relatively easier circular orbit.

The primary objective of the SpaDeX mission is to develop and demonstrate the technology needed for rendezvous, docking, and undocking of two small spacecraft (SDX01, which is the Chaser, and SDX02, the Target, nominally) in a low-Earth circular orbit. Secondary objectives include:

• Demonstration of the transfer of electric power between the docked spacecraft, which is essential for future applications such as in-space robotics,
• Composite spacecraft control, and
• Payload operations after undocking.

SpaDeX-2 Mission

• indian Space Research Organisation readies SpaDeX-2 mission to dock satellites in elliptical orbit. 
• Docking is critical for India’s upcoming Chandrayaan-4 mission and the proposed Bharatiya Antariksh Station, the country’s planned space station.
• One of the objectives of the mission includes demonstration of the transfer of electric power between the docked spacecraft, which is essential for future applications, such as in-space robotics, composite spacecraft control and payload operations after undocking.
• Docking is simpler in a circular orbit as satellite speed and path remain constant, unlike in an elliptical orbit, where they continuously change, making earlier calculations quickly outdated.

What is Docking

• Docking is the process of bringing two fast-moving spacecraft into the same orbit, moving them close to each other—either manually or automatically—and then connecting them. 
• This skill is essential for missions involving large spacecraft that are too heavy to be launched all at once by a single rocket.
• Over the years, space agencies have used various types of docking mechanisms, some of which are compatible with each other. 
• Spacecraft visiting the International Space Station (ISS) use the International Docking System Standard (IDSS), which was established in 2010.
• India uses an androgynous docking mechanism, meaning both the Chaser and Target satellites have identical systems. 
• While this is similar to the IDSS used by other countries, the Indian system uses only two motors, compared to the 24 motors used in the IDSS.

Future Missions

Chandrayaan-4 Mission: Chandrayaan-4, India’s lunar sample return mission, will likely use multiple modules launched separately, requiring docking in lunar or Earth orbit. Mastering elliptical orbit docking is key to these complex maneuvers.

• For its Moon missions, ISRO usually places spacecraft in an elliptical Earth orbit first. 
• It then performs engine burns at the perigee (the closest point to Earth) to gradually raise the apogee (the farthest point). 
• This fuel-efficient method helps set up a slingshot trajectory toward the Moon. 
• As a result, docking in elliptical orbits becomes a necessary skill for carrying out such complex missions.

Bharatiya Antariksh Station (BAS): India’s planned space station, set for 2035, will be modular, with parts launched separately and docked in orbit, demanding precise and reliable docking systems.

Mains Practice Question

Discuss the significance of orbital docking in space missions. In the context of ISRO’s lunar missions, explain the challenges and necessity of performing docking operations in elliptical orbits. (10M, 150W)