ISRO Reports 1.5 Lakh Satellite Collision Alerts in 2025

General Studies Paper III: Space Technology & Related Challenges

Why in News?

According to the Indian Space Situational Awareness Report (ISSAR), ISRO reported over 1.5 lakh satellite collision alerts in 2025, highlighting severe orbital congestion due to rising satellites and space debris.

Highlights of Indian Space Situational Awareness Report (ISSAR) 2025

Exponential Growth in Satellite Launches: The year 2025 recorded 315 successful launches, placing around 4,198 operational satellites into orbit, marking the highest activity in space history.
- Additionally, 4,651 new space objects were added in a single year, compared to 2,963 in 2024 and 3,135 in 2023, reflecting a sharp acceleration in satellite deployment trends.
LEO as Most Congested Zone: The Low Earth Orbit (LEO), ranging from 160–2000 km, has emerged as the most crowded orbital region due to its suitability for communication and Earth observation satellites.
- Reports indicate over 1.6 lakh close-approach alerts globally, with LEO contributing the majority, highlighting severe congestion and reduced orbital spacing.
Mega-Constellations Driving Satellite Proliferation: A major driver of congestion is the rise of mega-constellations, where companies deploy hundreds of satellites in a single launch cycle.
- This has compressed orbital lanes, significantly reducing reaction time for collision avoidance and increasing frequency of near-miss events.
Surge in Collision Alerts: Indian satellites alone faced over 1.5 lakh collision alerts in 2025 by the CSpOC of US Space Command, indicating an unprecedented density of objects in orbit.
- Globally, alerts crossed 1.6 lakh, showing that space is transitioning into a high-risk operational environment resembling a “traffic grid”.
Increasing Space Object Population: Despite 1,911 objects re-entering Earth’s atmosphere in 2025, the net population in orbit continues to grow, leading to orbital crowding beyond sustainable limits.
- Among the re-entered objects in 2025: 1,002 were known spacecraft, 657 were debris objects, 108 were rocket bodies and 144 were of unknown nature.
Indian Space Inventory: By the end of 2025, India’s footprint included 144 launched spacecraft. Currently, there are 86 Indian satellites in orbit: 27 are operational, 23 are defunct but remaining in space, and 36 have decayed.
- The Indian government specifically owns 22 satellites in Low Earth Orbit (LEO) and 31 in Geosynchronous Earth Orbit (GEO).
Space Debris Profile: Indian rocket bodies contribute significantly to trackable debris. The report identifies 42 parts of the PSLV, 4 parts of the GSLV, and 3 parts of the LVM-3 remaining in orbit. In 2025 alone, 12 Indian objects re-entered the atmosphere through controlled or natural decay.

Risks from Space Satellite Debris Collisions

Massive Debris Population: The orbital environment contains 44,800 tracked objects (>10 cm), along with 1.2 million fragments (1–10 cm) and over 140 million particles (<1 cm). This vast, unevenly tracked population significantly increases the probability of random high-speed collisions.
High-Velocity Impact Damage: Space debris travels at extreme speeds of 7–15 km/s, meaning even tiny fragments carry immense kinetic energy. A 1 cm object can disable a satellite, while a 10 cm object can completely destroy it, making collisions highly destructive.
Untracked Small Debris Threat: The most dangerous category is 1–10 cm debris, which is too small to track but large enough to destroy spacecraft. These objects evade monitoring systems, creating invisible collision risks that cannot be predicted or avoided effectively.
Kessler Syndrome: Collisions generate thousands of new fragments, leading to a self-sustaining chain reaction known as Kessler Syndrome. Over 500 fragmentation events have already contributed to debris growth, increasing the risk of runaway orbital instability.
Operational and Economic Losses: A single collision can destroy multi-million-dollar satellites, disrupt communication, navigation, and weather services, and require costly collision avoidance manoeuvres (fuel consumption), reducing satellite lifespan and increasing mission costs.
Risk to Human Life and Earth: Large debris can survive re-entry, with 20–40% of mass reaching Earth’s surface, posing risks to human populations and aviation safety. Additionally, debris is the top threat to human spaceflight missions, including astronauts aboard spacecraft.

India’s Space Surveillance and Safety Measurements

Space Situational Awareness: ISRO has established a multi-layered Space Situational Awareness (SSA) framework to safeguard its ₹1 trillion space infrastructure from a rapidly congesting orbital environment, which saw over 1.6 lakh alerts globally in 2025.
Nodal Management: The ISRO System for Safe and Sustainable Operations Management (IS4OM), operational since 2022, serves as the central hub for protecting national assets.
- It coordinates all debris-related activities, ensuring that India’s space operations align with United Nations (UN) and IADC guidelines for long-term sustainability.
Project NETRA: Under Project NETRA, ISRO is building a high-precision surveillance network to reduce dependence on foreign data like NORAD.
- The sanctioned project includes a 1,500 km range radar and optical telescopes at strategic locations like Hanle, Ladakh, to track objects as small as 10 cm.
DFSM 2030: The Debris Free Space Mission (DFSM) 2030 is an ambitious initiative to achieve zero debris from all Indian space actors by 2030.
- This mandate requires satellites and rocket stages to be de-orbited or moved to graveyard orbits with a success probability of over 99% within five years of mission end.
Active Mitigation: ISRO integrates passivation into its launch vehicles, such as the PSLV and GSLV, to prevent accidental explosions by venting residual fuel.
- PSLV Orbital Experimental Module (POEM) repurposes spent rocket stages as stabilized scientific platforms. This “zero-waste” approach prevents abandoned boosters from becoming debris.
- In 2025, these measures protected against fragments from 129 trackable debris pieces currently originating from Indian missions.
Conjunction Analysis: Daily Space Object Proximity Analysis (SOPA) is performed to identify potential threats.
- In 2025, ISRO executed 18 Collision Avoidance Manoeuvres (CAMs)—14 in LEO and 4 in GEO—to safeguard operational satellites like NISAR from critical close approaches.
Launch Windows: To ensure safe deployment, Collision Avoidance Analysis (COLA) is mandatory before every launch. This process requires shifting launch timings by seconds or minutes to avoid debris clouds, as demonstrated in the LVM3-M6 mission.
Remediation R&D: India is actively researching Active Debris Removal (ADR) technologies, including the SpaDeX mission for autonomous docking. These efforts focus on robotic arm development and rendezvous operations to eventually retrieve or push defunct satellites out of crowded orbits.

Global Governance and Management Framework:

IADC Space Debris Mitigation Guidelines (2002): Mandates limiting debris release, preventing in-orbit breakups, and ensuring post-mission disposal (e.g., the 25-year deorbit rule for LEO). These are technical guidelines adopted voluntarily to minimize the creation of new debris.
UNCOPUOS Space Debris Mitigation Guidelines (2007): Endorsed by the UN General Assembly, these 7 guidelines cover mitigation, safety, and operation, focusing on reducing long-term risks, and are now standard international practice.
UN Long-Term Sustainability (LTS) Guidelines: These guidelines provide a framework for safe space operations, emphasizing international cooperation, information sharing, and sustainable practices for outer space activities.
Outer Space Treaty (1967): Establishes the foundational legal requirement that states are responsible for their national space activities and liable for damage caused by their space objects.
Liability Convention (1972): Elaborates on the 1967 Treaty, establishing a legally binding framework for compensation if a space object causes damage, including space debris impact, making a launching state liable for its objects in space.