India’s space ambitions are growing rapidly, and with each passing year, the country is inching closer to becoming a key player in global space exploration. One of the latest and most exciting developments in this journey is the SpaDeX mission, which will make India only the fourth country in the world to demonstrate in-space docking technology. In-space docking is critical for future space missions that require the assembly or operation of multiple spacecraft. As India gears up for complex space initiatives like lunar exploration and the construction of the Bharatiya Antariksh Station (BAS), the SpaDeX mission is set to play a crucial role in pushing these boundaries further.

SPADEX Mission is scheduled on 30th December 2024 at 21:58 hrs IST from SDSC SHAR, Sriharikota

Understanding the SpaDeX Mission

The SpaDeX mission is an ambitious project by ISRO, designed to demonstrate the key technology needed for two small spacecraft to meet, dock, and separate in space. The mission will be launched aboard the PSLV-C60 rocket, with two spacecraft—SDX01 (the Chaser) and SDX02 (the Target)—each weighing about 220 kg. 

At its core, the mission will prove the capability of two spacecraft to dock in space with high precision. This technology is pivotal not only for India’s aspirations of lunar exploration, but also for future missions like the construction of space stations, sample returns from celestial bodies, and the launch of large-scale space exploration projects.

Mission Objectives: Pioneering Innovations in Space

The primary goal of the SpaDeX mission is to demonstrate:

1. Rendezvous and docking of two small spacecraft: SDX01 (Chaser) and SDX02 (Target).
2. Undocking and independent operations post-separation.

The secondary objectives include:

• Demonstrating electric power transfer between docked spacecraft, essential for future robotic and manned missions.
• Showcasing composite spacecraft control for optimized operations.
• Testing payload functionality post-undocking, with a projected mission life of two years.

How SpaDeX Works: A Step-by-Step Breakdown

The mission involves two identical spacecraft, each weighing approximately 220 kg, launched into a 470 km low-Earth orbit at a 55° inclination. Here’s how the operation unfolds:

1. Far Rendezvous Phase

• Post-launch, the Target and Chaser satellites achieve a separation of 10–20 km, facilitated by incremental velocity changes using the Target's propulsion system.
• This phase ensures precise alignment of orbital velocities and positions, setting the stage for closer maneuvers.

2. Close Rendezvous Phase

• The Chaser spacecraft gradually closes the gap with the Target, reducing distances incrementally to 5 km, 1.5 km, 500 m, 225 m, 15 m, and finally, 3 m.

3. Docking and Undocking

• At close ranges, cutting-edge navigation systems take over.
  • Laser Range Finders guide the spacecraft from 5 km to 0.25 km.
  • Docking Cameras and Visual Cameras ensure precision during the final approach.
• Retroreflectors on the Target spacecraft provide visual markers for onboard cameras, enabling real-time navigation adjustments.
• After docking, power transfer systems are tested, and the spacecraft subsequently undock to operate independently.

These technologies, developed in India, have been meticulously integrated into the spacecraft designed at the UR Rao Satellite Centre. Additionally, Ananth Technologies in Bengaluru handled the integration and testing phases to ensure the mission’s success.

To successfully dock, ISRO will rely on a sophisticated set of algorithms that estimate relative navigation, attitude, and velocity to guide the spacecraft with pinpoint accuracy. This complex control system will handle both translational and rotational dynamics to ensure that the docking is safe and precise.

India’s Growing Space Ambitions

The successful demonstration of in-space docking technology will be a massive leap forward for India’s space program. It will not only enhance the country’s space exploration capabilities but also play a vital role in missions that involve multiple spacecraft, such as lunar expeditions, sample returns, and even the creation of permanent space stations.

Once the SpaDeX mission successfully demonstrates docking capabilities, the next phase will likely focus on extending these technologies for use in larger spacecraft and for more complex space missions. With SpaDeX, the future of Indian space exploration is brighter than ever.