ISRO Completes Historic SPADEX Mission as Both Satellites Re-enter Earth’s Atmosphere After Successful Space Docking Experiments

The Indian Space Research Organisation (ISRO) has confirmed the successful conclusion of its historic Space Docking Experiment (SPADEX) mission, with both satellites re-entering Earth’s atmosphere on 12 October 2026 after completing their operational objectives. The two spacecraft, SPADEX-A and SPADEX-B, had successfully demonstrated several critical technologies, including autonomous rendezvous, docking, undocking, coordinated spacecraft control, electrical power transfer and orbital circumnavigation.

Announcing the development on 23 October 2026, ISRO stated that both satellites remained operationally healthy until their final telemetry transmissions. The mission represents a significant achievement in India’s space technology programme, having demonstrated indigenous capabilities essential for complex orbital operations, future space stations and missions involving multiple spacecraft.

The successful conclusion of SPADEX strengthens India’s technological foundation for more ambitious space exploration programmes, particularly those requiring spacecraft to approach, connect and operate together in orbit.

SPADEX Mission Launched Aboard PSLV-C60 in December 2024

ISRO launched the SPADEX mission on 30 December 2024 aboard the Polar Satellite Launch Vehicle PSLV-C60 from the Satish Dhawan Space Centre at Sriharikota. The launch vehicle placed the two spacecraft into a circular orbit approximately 470 kilometres above Earth, with an orbital inclination of 55 degrees.

The mission consisted of two small spacecraft weighing approximately 220 kilograms each. SPADEX-A, also designated SDX01, served as the Chaser spacecraft, while SPADEX-B, designated SDX02, functioned as the Target spacecraft during the primary docking experiment.

The spacecraft were designed to demonstrate the technologies required for two independently orbiting satellites to approach one another, establish a stable connection and subsequently separate in a controlled manner. These operations demand highly accurate navigation, communication, propulsion and automated control systems.

ISRO developed SPADEX as a cost-effective technology demonstration mission to establish essential capabilities for future Indian space programmes. The mission’s success enabled India to become the fourth country to demonstrate spacecraft docking technology in orbit.

India Successfully Demonstrates Autonomous Spacecraft Docking

One of the mission’s most important achievements was the successful demonstration of autonomous rendezvous and docking between the two satellites. ISRO accomplished the first docking of SPADEX-A and SPADEX-B on 16 January 2025, marking a major milestone in India’s space technology development.

Spacecraft docking involves bringing two independently orbiting vehicles together with extremely high precision. Both spacecraft must carefully regulate their relative positions and velocities before making contact, ensuring that the connection occurs without damaging either vehicle.

The SPADEX mission demonstrated low-impact docking technology, allowing the spacecraft to establish a secure mechanical connection after completing the necessary approach and alignment manoeuvres.

ISRO also demonstrated vertical and radial docking capabilities during the mission. These experiments helped validate different aspects of relative spacecraft positioning, approach control and docking operations.

The successful demonstrations provided India with practical experience in technologies that are essential for assembling orbital infrastructure and conducting missions involving multiple spacecraft.

Successful Undocking and Repeated Docking Demonstrations

Following the first successful docking operation, ISRO conducted additional experiments to evaluate the performance of the two spacecraft and their associated systems.

On 13 March 2025, ISRO successfully undocked the SPADEX satellites during its first attempt. The operation took place in a circular orbit approximately 460 kilometres above Earth, allowing the spacecraft to separate safely and resume independent orbital operations.

The undocking demonstration confirmed India’s ability to reverse the docking process while maintaining control over both spacecraft. The operation required precise coordination of mechanical release systems, spacecraft positioning and subsequent separation manoeuvres.

ISRO subsequently carried out further docking experiments, including a second successful docking demonstration and electrical power transfer between the connected spacecraft.

These achievements established practical capabilities for repeated orbital operations rather than limiting the mission to a single docking event. The experiments also allowed engineers to assess spacecraft performance under different operational conditions.

SPADEX Demonstrates Composite Control and Power Transfer Between Satellites

Beyond docking and undocking, the SPADEX mission successfully demonstrated composite spacecraft control and electrical power transfer, two technologies important for future space infrastructure.

Composite control involves managing two docked spacecraft as a single combined system. Once the satellites establish a mechanical connection, their control systems must account for the changed mass distribution, orientation and dynamic characteristics of the connected structure.

The successful demonstration showed that ISRO could maintain coordinated control of the joined spacecraft during orbital operations. Such capabilities are essential for space stations, where visiting spacecraft must connect to larger orbital structures without disturbing their stability.

SPADEX also demonstrated the transfer of electrical power between the docked satellites. This capability allows connected spacecraft to exchange energy through their docking interface, supporting future applications involving orbital servicing and spacecraft systems that operate together.

ISRO identified power transfer as one of the mission’s important secondary objectives. Its successful demonstration contributed to India’s growing expertise in spacecraft interfaces and integrated orbital operations.

Orbital Circumnavigation Adds Another Achievement to SPADEX

ISRO also confirmed the successful demonstration of spacecraft circumnavigation during the mission. This involved controlled relative movement of one spacecraft around the other while maintaining the necessary positional awareness and separation.

Circumnavigation is an advanced form of proximity operation that requires accurate tracking, navigation and orbital control. Unlike conventional satellite manoeuvres, the operation focuses on the relative position and movement of two spacecraft rather than their individual trajectories around Earth.

The demonstration provided additional experience in autonomous spacecraft operations and helped validate technologies relevant to future rendezvous missions.

Such capabilities are particularly valuable for spacecraft inspection, orbital servicing and missions in which one vehicle must approach or move around another without making immediate physical contact.

By demonstrating rendezvous, docking, undocking, power transfer, composite control and circumnavigation within a single programme, SPADEX achieved a broad range of important technological objectives.

Both SPADEX Satellites Re-enter Earth’s Atmosphere on 12 October 2026

After completing their operational activities, both SPADEX satellites gradually approached the end of their orbital lifetimes. ISRO confirmed that the spacecraft had exhausted their onboard fuel following the mission’s operational phase.

Without sufficient propulsion capability to maintain their orbital conditions, both spacecraft experienced progressive orbital decay. Atmospheric drag gradually reduced their orbital altitude, bringing them closer to the denser layers of Earth’s atmosphere.

On 12 October 2026, both satellites re-entered Earth’s atmosphere, bringing their missions to a conclusion.

According to ISRO, SPADEX-A re-entered over the South Pacific Ocean at approximately 16:48 UTC, corresponding to 10:18 PM Indian Standard Time on 12 October.

SPADEX-B subsequently re-entered over the North Atlantic Ocean at approximately 23:36 UTC on the same date, corresponding to 5:06 AM Indian Standard Time on 13 October.

ISRO identified these oceanic regions as the respective impact locations associated with the spacecraft’s atmospheric re-entry.

The re-entry events marked the final stage of a mission that had successfully demonstrated a series of advanced orbital technologies following its launch in December 2024.

Geomagnetic Storms Accelerated the Satellites’ Orbital Decay

ISRO reported that two moderate geomagnetic storms occurring on 4 October and 11 October 2026 accelerated the orbital decay of both SPADEX satellites.

Geomagnetic storms occur when disturbances originating from solar activity interact with Earth’s magnetic environment. These disturbances can alter conditions in the upper atmosphere and influence the orbital behaviour of satellites operating at relatively low altitudes.

During periods of increased geomagnetic activity, heating and expansion of the upper atmosphere can increase atmospheric density at satellite orbital altitudes. This increases aerodynamic drag on spacecraft and can cause them to lose altitude more rapidly.

For the SPADEX satellites, the geomagnetic storms contributed to an acceleration of the orbital decay already occurring after the completion of their operational activities.

The events demonstrate the importance of monitoring space weather when assessing spacecraft trajectories and predicting atmospheric re-entry.

ISRO Maintained Satellite Health Until Final Telemetry Reception

An important aspect of the SPADEX mission’s conclusion was ISRO’s ability to maintain the health of both spacecraft until their final telemetry transmissions.

Telemetry provides information about a spacecraft’s operating condition, including the status of onboard systems and parameters required by ground controllers to assess its performance.

ISRO stated that careful mission management ensured both SPADEX-A and SPADEX-B remained healthy until the final telemetry frames were received.

The mission operations were supported by ISRO’s spacecraft monitoring and control infrastructure, including the ISRO Telemetry, Tracking and Command Network.

Maintaining spacecraft health throughout the mission allowed engineers to collect operational information across the satellites’ orbital lifetime. The data obtained during docking, undocking, proximity operations and subsequent orbital decay will contribute to ISRO’s experience in managing complex spacecraft missions.

Indigenous Technologies Developed for the SPADEX Mission

The SPADEX programme incorporated several technologies developed by ISRO to support autonomous rendezvous and docking operations.

These included an indigenous docking mechanism, specialised rendezvous sensors, electrical power transfer systems and an inter-satellite communication link that enabled the spacecraft to exchange information during orbital operations.

ISRO also developed autonomous guidance and control software capable of managing the complex sequence of approach manoeuvres required for docking.

The navigation strategy involved progressively reducing the distance between the spacecraft through carefully controlled orbital manoeuvres. Before docking, the satellites were required to maintain accurate relative positioning while approaching through a series of predefined separation distances.

The technologies underwent extensive ground testing and simulation before their deployment in orbit. These preparations helped ISRO evaluate the spacecraft systems and validate their performance under expected mission conditions.

The SPADEX spacecraft were designed and developed by the U R Rao Satellite Centre in Bengaluru with contributions from other ISRO centres. Integration and testing activities also involved Indian industry, demonstrating the participation of domestic manufacturing and engineering organisations in advanced space programmes.

SPADEX Technologies Support India’s Future Space Station Plans

The successful SPADEX mission provides an important technological foundation for India’s proposed Bharatiya Antariksh Station.

Space stations require reliable docking systems because crewed and uncrewed spacecraft must regularly approach, connect and separate from orbital modules. These operations are necessary for transporting personnel, equipment, scientific instruments and essential supplies.

The ability to control docked spacecraft as a combined system is also relevant to the assembly and operation of larger orbital structures.

Electrical power transfer and autonomous docking technologies can support spacecraft integration and reduce the complexity of certain orbital operations.

ISRO has identified space docking as a critical capability for its long-term ambitions, including the development of the Bharatiya Antariksh Station and future missions requiring multiple spacecraft to work together.

SPADEX has demonstrated several of the fundamental technologies required for these activities, providing valuable experience for the design and development of more advanced orbital systems.

Space Docking Technology Important for Future Lunar Missions

Beyond space station operations, autonomous rendezvous and docking technologies are important for future lunar exploration missions.

Certain complex space missions may require separate spacecraft modules to operate independently before joining together in orbit. These configurations can support mission architectures involving orbital assembly, transfer of materials and the movement of spacecraft between different operational phases.

ISRO has identified future lunar sample-return missions among the applications that could benefit from docking technology.

In such missions, spacecraft may need to coordinate their movement and establish precise connections to transfer collected materials or support subsequent mission operations.

SPADEX has provided India with practical experience in the fundamental technologies required for such activities. Further development and qualification will enable ISRO to adapt these capabilities for more demanding missions beyond low-Earth orbit.

SPADEX Marks a Major Milestone in India’s Space Technology Development

The successful completion of the SPADEX mission represents a significant achievement in India’s pursuit of advanced and increasingly autonomous space technologies.

From its launch aboard PSLV-C60 in December 2024 to the final atmospheric re-entry of both satellites in October 2026, the mission demonstrated a wide range of capabilities associated with complex orbital operations.

The successful docking and undocking experiments established India’s ability to connect and separate independently orbiting spacecraft. Additional demonstrations of composite control, electrical power transfer and circumnavigation expanded the technological achievements of the programme.

ISRO’s confirmation that both satellites remained healthy until their final telemetry reception also highlights the effectiveness of the mission’s operational management.

With SPADEX successfully concluded, India possesses valuable flight-tested experience in technologies essential for future orbital infrastructure, spacecraft servicing and ambitious exploration missions.

The mission’s achievements strengthen the technological foundation for the Bharatiya Antariksh Station, future lunar missions and India’s expanding programme of advanced space exploration.

References

1. Indian Space Research Organisation (ISRO). SPADEX Satellites Re-entry into Earth’s Atmosphere on October 12, 2026. Official announcement, 23 October 2026.
   https://www.isro.gov.in/SPADEX_Satellites_Re_entry_into_Earths_Atmosphere.html
2. Indian Space Research Organisation (ISRO). SpaDeX Mission. Official mission description, spacecraft specifications, objectives and indigenous technologies.
   https://www.isro.gov.in/mission_SpaDeX.html
3. Indian Space Research Organisation (ISRO). SPADEX Undocking Successful. Official announcement, 13 March 2025.
   https://www.isro.gov.in/spadex_undocking_successful.html
4. Department of Space, Government of India. Achievements During FY 2025–2026. Official report documenting SPADEX docking, undocking and electrical power transfer achievements.
   https://www.isro.gov.in/media_isro/pdf/Annexure_Achievements_during_FY_2025_2026.pdf
5. Department of Space, Government of India. Annual Report 2024–2025. Official documentation of PSLV-C60, SPADEX spacecraft development and India’s space docking programme.
   https://www.isro.gov.in/media_isro/pdf/AnnualReport/Annual_Report_2024_25_Eng.pdf