Rewind 2025: ISRO’s Missions, Milestones and Major Breakthroughs

The year 2025 stands out as one of the most transformative years in the history of the Indian Space Research Organisation (ISRO). From mastering space docking technology and strengthening navigation systems, to making rapid progress in the Gaganyaan human spaceflight programme and expanding India’s role in commercial space launches, ISRO achieved multiple historic milestones. The year firmly positioned India among the world’s leading spacefaring nations.

January 2025: India Enters the Elite Space Docking Club

ISRO began 2025 with a historic achievement by successfully docking two satellites in space under the SpaDeX (Space Docking Experiment) Mission.

SpaDeX Mission Highlights

• Launch Date: December 30, 2024 (PSLV)
• Docking Achieved: January 16, 2025

Satellites

• SDX01 – Chaser
• SDX02 – Target

After overcoming technical issues that led to postponements on January 7 and January 9, ISRO successfully reduced the inter-satellite distance step-by-step—from 20 km to just 3 metres—before achieving autonomous docking.

With this, India became the 4th country after the USA, Russia, and China to demonstrate satellite docking capability.

Why SpaDeX Matters

• Essential for Chandrayaan-4 lunar sample return
• Core technology for Bharatiya Antariksh Station
• Crucial for future human Moon missions

Post-docking, ISRO successfully tested power transfer and satellite separation, proving end-to-end capability.

January 2025: 100th Launch from Sriharikota – NavIC Strengthened

On January 29, 2025, ISRO achieved another historic milestone with its 100th launch from Sriharikota.

GSLV-F15 / NVS-02 Mission

• Launch Vehicle: GSLV-F15
• Payload: NVS-02 navigation satellite
• Orbit: Geosynchronous Transfer Orbit (GTO)

This mission strengthened India’s NavIC (Navigation with Indian Constellation) system.

About NVS-02

• Replaced IRNSS-1E
• Payloads in L1, L5, S bands
• Equipped with indigenous atomic clock
• Provides Position, Velocity & Timing (PVT) services

NavIC now supports,

• Defence & strategic operations
• Disaster management
• Shipping and rail safety

Time synchronisation for telecom and power sectors

February 2025: World’s Largest Propellant Mixer Developed

In a major boost to self-reliance, ISRO developed the world’s largest 10-tonne vertical planetary mixer for solid rocket motors.

Key Details

• Developed with: Central Manufacturing Technology Institute (CMTI), Bengaluru
• Handover Date: February 13, 2025
• Weight: ~150 tonnes
• Control: PLC-based automated system with SCADA monitoring

This mixer enhances safety, quality, and productivity in solid propellant production—vital for rockets like LVM3.

March–April 2025: Semicryogenic Engine Breakthrough

ISRO made major progress in advanced propulsion with semicryogenic engine hot tests at IPRC, Mahendragiri (Tamil Nadu).

Test Timeline

• First Hot Test: March 28, 2025
• Second Hot Test: April 24, 2025

Test Highlights

• Engine ignited successfully
• Operated at 60% rated power

Validated,

• Low & high-pressure turbo pumps
• Pre-burner
• Control systems

This engine will power future launch vehicles, improving payload capacity and reducing launch costs.

July 2025: Gaganyaan Propulsion System Validated

On July 3, 2025, ISRO conducted two hot tests of the Gaganyaan Service Module Propulsion System (SMPS).

SMPS Configuration

• 5 Liquid Apogee Motors (440 N each)
• 16 RCS thrusters (100 N each)
• Test Durations
• 30 seconds
• 100 seconds (full integrated test)

The system performed simultaneous firing of all thrusters, validating its readiness for orbital manoeuvres and abort scenarios, crucial for astronaut safety.

August 2025: Human Spaceflight Preparations Intensify

1. HOPE Mission – Space Simulation in Ladakh

• On August 1, 2025, ISRO launched a 10-day high-altitude isolation mission at 14,000 feet in Ladakh.
• Location: HOPE – Himalayan Outpost for Planetary Exploration
• Objective: Study human endurance under space-like conditions
• Crew: Two selected researchers
• Focus: Physical health, mental resilience, mission routines
• This marked India’s entry into planetary analogue research.

2. Integrated Air Drop Test (IADT-01)

• On August 24, 2025, ISRO successfully conducted the first Integrated Air Drop Test for Gaganyaan.
• Validated the parachute-based deceleration system
• Conducted with support from IAF, Navy, DRDO, Coast Guard
• Ensured safe crew module recovery during re-entry

December 2025: Countdown to Human Spaceflight

1. Vyommitra Ready for Uncrewed Mission

ISRO announced that Vyommitra, an AI-powered half-humanoid robot, will fly onboard an uncrewed Gaganyaan mission in December 2025.

Vyommitra will,

• Monitor cabin environment
• Operate control panels
• Simulate human presence

This mission will validate life support systems and safety protocols before astronauts fly.

2. Drogue Parachute Qualification Tests

• On December 18–19, 2025, ISRO completed drogue parachute tests at TBRL, Chandigarh.
• Gaganyaan deceleration system uses 10 parachutes
• Ensures stable re-entry and safe splashdown
• All performance objectives were met

3. BlueBird Block-2 Commercial Launch

• On December 24, 2025, ISRO launched the BlueBird Block-2 communication satellite using LVM3 ‘Baahubali’.
• Developed by AST SpaceMobile (USA)
• Enables direct-to-smartphone broadband connectivity
• Heaviest commercial payload launched from Indian soil
• Strengthened India’s position in the global commercial launch market