ISRO Launches EOS-05 on GSLV-F17: India’s First Imaging Satellite from Geosynchronous Orbit

The Indian Space Research Organisation (ISRO) successfully launched its Earth Observation Satellite EOS-05 aboard the Geosynchronous Satellite Launch Vehicle (GSLV)-F17 at 2:55 am IST on 4 September 2026 from the Second Launch Pad at Satish Dhawan Space Centre (SDSC) SHAR in Sriharikota, Andhra Pradesh. The 2,367 kg spacecraft is India’s first imaging satellite deployed from geosynchronous orbit, about 36,000 km above Earth, where it can stare continuously at the Indian subcontinent rather than passing over briefly like low orbit satellites. The mission strengthens domestic Earth observation and imaging capabilities with near real-time, high frequency coverage for disaster management, agriculture, environment and security.

What Is EOS-05?

EOS-05, short for Earth Observation Satellite-05, is a state of the art Earth observation spacecraft built by the Indian Space Research Organisation (ISRO). ISRO is India’s national space agency, headquartered in Bengaluru and operating under the Department of Space. It was established in 1969, succeeding INCOSPAR which was set up in 1962, and its first satellite Aryabhata was launched on 19 April 1975 with Soviet assistance.

EOS-05 is also designated GISAT-1A, where GISAT stands for Geo Imaging Satellite. It is the second satellite in the GISAT series and is built on ISRO’s proven I-2K (I-2000) satellite bus, a standardised platform that provides power, propulsion and control systems. The spacecraft has a launch mass of 2,367 kg and a designed mission life of 10 years, with multi-junction solar arrays generating more than 2,200 watts of power.

Unlike most Indian remote sensing satellites that operate in Low Earth Orbit (LEO) at 400 to 900 km and revisit a location only once or twice a day, EOS-05 is designed to operate from geosynchronous orbit at about 35,786 km altitude. From that height it appears almost fixed over the Indian region, enabling it to image a selected area every 5 minutes and the entire Indian landmass every 30 minutes under cloud free conditions. This high temporal resolution is its defining feature.

What Is GSLV-F17 and How Did It Place EOS-05 in Orbit?

GSLV stands for Geosynchronous Satellite Launch Vehicle. It is a three stage, medium lift launch vehicle developed by ISRO to carry communication and Earth observation satellites to Geosynchronous Transfer Orbit (GTO). The GSLV-F17 mission was the 19th flight of the GSLV series and used the GSLV Mk II configuration.

The vehicle is 51.7 metres tall and had a liftoff mass of 420.5 tonnes at launch. It lifted off after a 27.5 hour countdown and used a 4 metre diameter ogive composite payload fairing that protects the satellite during atmospheric flight. According to ISRO’s mission brochure, the flight injected the 2,367 kg EOS-05 into a Sub-Geosynchronous Transfer Orbit (Sub-GTO) with high precision. ISRO Chairman V. Narayanan and Mission Director Thomas Kurian confirmed the accurate injection, with Kurian noting it was the heaviest satellite the GSLV has ever placed into a transfer orbit.

The first stage burns with its four liquid strap-ons for about 100 seconds, followed by second stage ignition and finally the cryogenic upper stage which provides the high specific impulse needed to achieve transfer orbit velocity. For this mission, the planned Sub-GTO had a nominal perigee of 170 km, apogee of 28,934 km, inclination of 19.28 degrees and argument of perigee near 178 degrees, with a launch azimuth of 104 degrees.

What Is Sub-Geosynchronous Transfer Orbit?

A Sub-GTO is an elliptical transfer orbit with an apogee lower than the standard GTO apogee of about 36,000 km. Satellites injected into Sub-GTO use their own onboard propulsion to raise their orbit in steps to reach the final circular geosynchronous or geostationary orbit near 35,786 km altitude. For EOS-05, initial tracking showed an insertion orbit near 155 km by 30,970 km inclined at about 19.33 degrees, with a period near nine hours. After the first orbit raising manoeuvre on 5 September 2026, ISRO reported an orbit of about 20,000 km by 31,129 km. The satellite will steadily raise itself to its operational slot, reported to be around 85.5 degrees East over the Indian Ocean region.

What Is Geosynchronous Orbit and How Is It Different from Geostationary and Other Orbits?

Geosynchronous orbit is an orbit where a satellite takes exactly one sidereal day, about 23 hours 56 minutes, to circle Earth, so it returns over the same longitude each day. Its average altitude is about 35,786 km above the equator. Geostationary orbit is a special type of geosynchronous orbit that is both circular and equatorial with zero inclination. A geostationary satellite appears completely fixed above one point on the equator, while a geosynchronous satellite with inclination traces a small figure eight pattern but still remains over the same broad region.

This is different from other common orbits. Low Earth Orbit (LEO) lies at 160 to 2,000 km and satellites there circle Earth in about 90 to 120 minutes, passing over a location only periodically. Sun-synchronous orbit, a type of polar orbit at 600 to 900 km, passes over any point at the same local solar time and is favoured for conventional Earth observation because it gives consistent lighting. Polar orbit passes over the poles and covers the whole globe over days, while LEO and sun-synchronous missions revisit a spot only after hours or days.

Geosynchronous Transfer Orbit (GTO) and Sub-GTO are not operational orbits but elliptical transfer paths that connect LEO height perigee to geosynchronous height apogee. Geosynchronous orbit (GSO) and Geostationary orbit (GEO) are the final circular destinations near 35,786 km where the satellite’s angular speed matches Earth’s rotation.

For imaging, this position is a trade off. From 36,000 km the amount of light per pixel is much lower than from LEO, so spatial resolution is coarser. EOS-05 compensates with a large 700 mm Ritchey-Chretien telescope, the same optical design family used in the Hubble Space Telescope, adapted from Cartosat-2A, to achieve usable resolution from that distance.

GSLV vs PSLV vs LVM3 vs SSLV: How Do India’s Rockets Compare?

ISRO now operates four active launch vehicles. Understanding their differences explains why GSLV was chosen for EOS-05.

PSLV stands for Polar Satellite Launch Vehicle. It has four stages with alternating solid and liquid propulsion, uses Vikas engines, and has no cryogenic stage. It is optimised for Sun-synchronous and polar orbits and is ISRO’s most reliable workhorse, famous for launching Chandrayaan-1 in 2008, Mangalyaan in 2013, Aditya-L1 and a record 104 satellites in one flight in 2017.

GSLV, the Geosynchronous Satellite Launch Vehicle, is a three stage vehicle with a solid core, liquid second stage and indigenous cryogenic upper stage (CE-7.5 using LH2 + LOX). It is built to lift about 2,250 kg to GTO and 6,000 kg to LEO. The GSLV project began in 1990 to give India independent access to high orbits for INSAT and GSAT communication satellites. Early GSLV Mk I flights used a Russian KVD-1 cryogenic engine, while Mk II from 5 January 2014 (GSLV-D5) onwards flies the indigenous CE-7.5. GSLV is 51.7 metres tall and is still the tallest vehicle in ISRO’s fleet.

LVM3, or Launch Vehicle Mark 3, earlier called GSLV Mk III, is India’s heaviest rocket, also known as Bahubali. It uses two S200 solid strap-ons, an L110 core with twin Vikas engines and a C25 cryogenic stage with the more powerful CE-20 engine. It can place 4,000 kg to GTO and 8,000 kg to LEO and is human rated for the Gaganyaan crewed mission. It launched Chandrayaan-2 and Chandrayaan-3, which landed near the lunar south pole in 2023.

SSLV, the Small Satellite Launch Vehicle, is a compact three solid stage vehicle plus a Velocity Trimming Module (VTM) for on demand, low cost launches of up to 500 kg to LEO and 300 kg to Sun-synchronous orbit with turnaround of days.

GSLV-F17’s success therefore validates the CE-7.5 cryogenic stage, whose thrust was improved by about 6 percent in later versions, and restores confidence after the GSLV-F10 failure in August 2021 when the cryogenic stage failed to ignite and EOS-03 (GISAT-1) was lost.

Where Did the Launch Take Place? Satish Dhawan Space Centre at Sriharikota

The launch took place from the Second Launch Pad (SLP) at the Satish Dhawan Space Centre (SDSC) SHAR in Sriharikota, Tirupati district, Andhra Pradesh. SHAR originally stood for Sriharikota Range and the centre was renamed on 5 September 2002 in memory of Satish Dhawan, former Chairman of ISRO. It lies on a barrier island between Pulicat Lake and the Bay of Bengal, about 80 km north of Chennai, at coordinates near 13.72 degrees N, 80.23 degrees E.

The island was chosen in 1969 for a launch station and became operational on 9 October 1971 with the launch of an RH-125 sounding rocket. The first orbital attempt was Rohini 1A on SLV on 10 August 1979. Today SDSC SHAR is India’s primary spaceport and handles all orbital launches. It has two operational pads. The First Launch Pad (FLP), built in the early 1990s, hosted the first PSLV flight on 20 September 1993. The Second Launch Pad, designed and built by MECON Limited, Ranchi between March 1999 and December 2003 at a cost of about ₹400 crore, became operational on 5 May 2005 with PSLV-C6 Cartosat-1. It is a universal pad capable of handling PSLV, GSLV and LVM3.

The centre provides solid propellant processing, vehicle integration, range operations, telemetry, tracking and mission control. It is headed by the Director, SDSC SHAR, currently S. Muthuchezhian, and operates under ISRO Headquarters at Antariksh Bhavan, Bengaluru. To meet rising launch demand, the Union Cabinet approved a Third Launch Pad on 16 January 2025 at a cost of about ₹3,984.86 crore, to be ready by 2029-30 for Next Generation Launch Vehicles (NGLV) and as a standby for the Second Pad. A private pad ALP-01 Dhanush for Agnibaan vehicles was also inaugurated in November 2022.

What Makes EOS-05 Special? Payloads, Imaging Power and Uses

EOS-05 carries an advanced optical payload built around a 700 mm Ritchey-Chretien telescope. The focal plane uses array detectors split across three imaging modes that together give both broad colour and chemically specific information.

Multispectral means a handful of broad colour bands that map vegetation, water and land use. Hyperspectral splits light into hundreds of very narrow, contiguous bands just a few nanometres wide. Each pixel gets a full spectral fingerprint that can identify specific materials such as crop stress, mineral deposits, soil moisture or fire signatures, not just broad colours. With 414 combined hyperspectral channels, EOS-05 is the first hyperspectral surface imager planned to operate from geosynchronous altitude for land observation. Other geostationary weather satellites such as US GOES with 16 channels, Europe’s Meteosat or Japan’s Himawari-9, and even the European MTG-S1 hyperspectral sounder launched 1 July 2025, profile the atmosphere, not the land surface.

The platform is agile and jitter free, with an electronically steerable antenna, allowing rapid repointing. It can provide a selected field image every 5 minutes and a full Indian landmass image every 30 minutes at 42 metres resolution, a cadence that low orbit satellites cannot match.

Applications are wide. For disaster management, continuous tracking of cyclones, floods, cloudbursts, landslides and forest fires supports early warning and response. For agriculture and forests, it enables crop health, vegetation, soil moisture, snow and glacier monitoring. For environment and oceans, it helps coastal change and ecosystem assessment. For strategic monitoring, persistent viewing of border and maritime areas improves situational awareness. Science and Technology Minister Jitendra Singh described EOS-05 as enabling advanced imaging across visible, infrared, multispectral and hyperspectral bands.

From geosynchronous height, resolution is naturally limited to tens of metres, so EOS-05 does not replace sub-metre LEO imagers such as Cartosat or RISAT. Its value is persistence and spectral depth, not sharpest spatial detail, and it works only under cloud free conditions for optical bands.

From GISAT-1 Failure to EOS-05 Success: Mission Context and Significance

The GISAT programme was conceived to give India uninterrupted observation of the subcontinent. The first satellite, GISAT-1 (EOS-03), launched on GSLV-F10 on 12 August 2021, but was lost when the cryogenic upper stage failed to ignite. That failure delayed India’s geosynchronous imaging capability by five years. EOS-05 (GISAT-1A) was built as its direct replacement with design updates informed by that review.

Its success on 4 September 2026 therefore has several layers of importance. First, it restores and establishes for the first time an operational geosynchronous imaging capability, placing India in a small group of nations with continuous geosynchronous Earth observation. Second, it is a programme milestone for GSLV itself. GSLV-F17 is the 19th flight of the GSLV family since the first flight on 18 April 2001, and the mission proved the vehicle can now inject 2,367 kg to Sub-GTO, about 54 percent more than the 1,536 kg carried by GSLV-D1, showing steady growth in cryogenic stage performance.

Third, it clears the way for upcoming missions. With this launch complete, ISRO can now advance the NVS-03 navigation satellite for the NavIC constellation, which currently operates below the minimum four satellites needed for continuous three dimensional positioning, and prepare for other GSLV flights planned in 2026.

Prime Minister Narendra Modi called the launch a proud moment and a reflection of the excellence and growing capabilities of India’s space sector. He also highlighted the growing partnership between ISRO and Indian industry as adding new strength and scale to the entire space ecosystem, a theme echoed in ISRO’s increasing collaboration with private firms under the Indian Space Policy 2023.

The Way Forward

EOS-05 will now undergo a series of orbit raising manoeuvres using its onboard liquid apogee motor to circularise at geosynchronous altitude, followed by solar panel deployment, payload commissioning and calibration. Data will flow to ISRO’s National Remote Sensing Centre (NRSC) in Hyderabad, Space Applications Centre (SAC) in Ahmedabad and the ISRO Telemetry Tracking and Command Network (ISTRAC) in Bengaluru, and is expected to be shared with agencies for disaster warning, agriculture advisories and environmental monitoring. The speed at which calibrated hyperspectral products become available to civilian users will determine how quickly the mission translates into field level benefits.

ISRO’s launch schedule remains active. After GSLV-F17, attention shifts to NavIC replenishment, further PSLV Earth observation launches and the Gaganyaan human spaceflight programme using human rated LVM3. Steady success of the indigenous cryogenic stage also strengthens confidence for future high altitude missions and for commercial launch opportunities from Sriharikota’s expanded pad infrastructure.

Key Takeaways

• EOS-05 (GISAT-1A) was launched on 4 September 2026 at 2:55 am IST aboard GSLV-F17, the 19th flight of the GSLV family, from the Second Launch Pad at SDSC SHAR, Sriharikota.
• EOS-05 is India’s first imaging satellite from geosynchronous orbit at about 35,786 km altitude, built on the I-2K bus with a 2,367 kg mass and a 10 year mission life.
• The launch vehicle GSLV-F17 is a 51.7 m, 420.5 tonne, 3 stage rocket with S139 + 4 L40H, GL40HT (Vikas) and CUS15 (CE-7.5 cryogenic) stages and a 4 m ogive fairing.
• The satellite was injected into a Sub-Geosynchronous Transfer Orbit (Sub-GTO) with nominal 170 km perigee and 28,934 km apogee and will be raised to a geosynchronous slot near 85.5 degrees East.
• EOS-05 carries a 700 mm Ritchey-Chretien telescope with multispectral VNIR (6 channels, 42 m) and hyperspectral VNIR (158 channels, 318 m) and SWIR (256 channels, 191 m) payloads, imaging a selected area every 5 minutes and all of India every 30 minutes.
• The mission replaces the failed EOS-03 (GISAT-1) on GSLV-F10 in August 2021 and is the heaviest payload ever placed by GSLV into a transfer orbit, marking a 54 percent increase over GSLV-D1’s 1,536 kg in 2001.