India is set to achieve a significant milestone in its space exploration efforts with the launch of the Space Docking Experiment (SpaDEx) on December 30, 2024. The Indian Space Research Organisation (ISRO) will conduct this mission using the PSLV-C60 rocket, scheduled to lift off from Sriharikota at 9:58 PM IST.

The Space Docking Experiment (SpaDEx) is a significant mission conducted by the Indian Space Research Organisation (ISRO), aimed at demonstrating advanced techniques for autonomous rendezvous and docking of spacecraft. Scheduled for late December 2024, this mission involves two identical satellites: the Chaser (SDX01) and the Target (SDX02), each weighing approximately 220 kg. They will operate in a low-Earth orbit at an altitude of 470 km with a 55° inclination.

The primary objectives of the SpaDEx mission include:

Demonstrating Precision Manoeuvres: The mission will showcase the ability to perform precise manoeuvres necessary for rendezvous and docking between the two satellites.

Electrical Power Transfer: It aims to validate the transfer of electrical power between the docked spacecraft, which is crucial for future missions requiring in-space servicing.

Post-Docking Operations: After undocking, both spacecraft will operate their respective payloads, extending their mission life up to two years.

Key Technologies And Techniques

Docking Mechanism

The docking system employed in SpaDEx is characterized by:

Low-Impact Docking: The approach velocity is designed to be around 10 mm/s, ensuring minimal impact during docking.

Androgynous Design: Both spacecraft utilize identical docking systems, facilitating easier operations.

Peripheral Docking System: This design is similar to the International Docking System Standard, allowing for compatibility with other space missions.

Sensor Suite

A sophisticated sensor suite is integral to the SpaDEx mission:

Laser Range Finder (LRF): This sensor operates over a range of 6000 m to 200 m, determining both range and relative velocity.

Rendezvous Sensors (RS): These sensors provide relative position data within ranges from 250 m down to 10 m.

Proximity and Docking Sensors (PDS): They function effectively over a range from 30 m to 0.4 m, crucial for final approach and docking phases.

Algorithms For Rendezvous And Docking

The mission employs advanced algorithms for effective rendezvous and docking:

V-bar Strategy: This strategy uses multiple pulses to control the approach trajectory of the chaser satellite towards the target.

Guidance Algorithms: These algorithms are designed to maintain fixed inter-satellite distances during various phases of the docking process, ensuring accurate alignment and approach.

The SpaDEx mission represents a pivotal step in India's capabilities in space exploration and technology. By mastering orbital alignment dynamics and demonstrating autonomous docking techniques, ISRO is positioning itself at the forefront of future space missions, including potential lunar explorations. The success of SpaDEx could pave the way for more complex operations in space, such as in-orbit assembly and satellite servicing, which are essential for advancing human presence beyond Earth.

ISRO