Context:

India’s SpaDeX mission is set for launch on December 30, using the PSLV-C60 rocket from the Satish Dhawan Space Centre in Sriharikota.

About the SpaDeX Mission

The SpaDeX mission is a cost-effective technology demonstration to showcase in-space docking using two small spacecraft.

It consists of two small spacecraft, Chaser (SDX01) and Target (SDX02) will be placed into a circular low-Earth orbit at 470 km.

• The Chaser (SDX01) satellite has a high-resolution camera on board that’s a miniature version of a surveillance camera. 

The Target (SDX02) satellite will carry a multispectral payload that will be used for monitoring natural resources and vegetation along with a radiation monitor that will study space radiation and create a database. 

The Final stage of the launch vehicle will carry 24 additional payloads, including:

• A robotic arm to capture space debris
• An experiment to study seed germination and plant growth in space

Objectives

Primary Goal: To demonstrate the rendezvous, docking, and undocking of two spacecraft.

Secondary Goals:

• Enable electric power transfer between the spacecraft for future robotic missions.
• Manage spacecraft control and payload operations after undocking.
• Conduct microgravity experiments using PSLV's spent fourth stage PSLV Orbital Experimental Module (POEM-4).

Docking process of SpaDeX mission

• Initial separation: After launch, both satellites will be placed in a 470 km orbit, initially separated by 10 to 20 km.
• Far Rendezvous: The target satellite’s propulsion system will prevent further drift, keeping both satellites at a 20 km separation as they continue at the same velocity.
• Approach and Docking: The Chaser satellite will progressively reduce the distance to the Target satellite in stages, from 20 km to 3 meters, before docking.
• Docking and Power Transfer: Once docked, the satellites will demonstrate electrical transfer and coordinated control between them.
• Separation and Payload Operations: After docking, the satellites will separate and continue to operate their payloads for 2 years.

Key Technologies in Play:

• Docking Mechanism: A low-impact, docking system with two motors.
• Sensor Suite: Advanced sensors like Laser Range Finder (LRF), Proximity and Docking Sensor (PDS), and video monitors for precise docking.
• Relative Orbit Determination (ROD) Processor: A Global Navigation Satellite System (GNSS)-based system for accurate position and velocity tracking between the spacecraft.

Significance of this mission:

• Advancing Space Research: The SpaDeX mission will support India's future space ambitions, such as Chandrayaan-4, lunar sample-return missions, and the Bharatiya Antariksh Station (MAS).
• Technological Achievement: This mission will make India the fourth country in the world to possess space docking technology (After the US, Russia, and China).