‘Naughty Boy’ Countdown Begins: ISRO’s ‘Eye In The Sky’ Set For 36,000-Km Journey In A Mission Five Years In The Making

New Delhi: At 2:55 am on Friday, September 4, the spotlight will turn to Sriharikota as the Indian Space Research Organisation (ISRO) prepares for a launch that carries significance far beyond the satellite sitting atop its rocket.   

The GSLV-F17 is set to launch from the Satish Dhawan Space Centre's Second Launch Pad, carrying EOS-05, a highly advanced Earth observation satellite that will be India's first image satellite to operate in geosynchronous orbit. 

The launch comes at an especially crucial time for ISRO. Following a series of setbacks with its Polar Satellite Launch Vehicle (PSLV), which was formerly regarded as one of the world's most reliable rockets, the agency has entered a challenging phase. With the PSLV now grounded while investigations and tests are underway, the success of GSLV-F17 might provide a significant boost to confidence in India's space program.

However, the two launchers belong to separate families and have different propulsion systems. The PSLV's recent issues are thus not directly related to the GSLV Mk II, allowing Friday's mission to be evaluated on its own technical merits.

Why this GSLV mission is being watched closely

The GSLV has a complex history. Inside ISRO, it is popularly known as the "naughty boy" because to its inconsistent performance during its development years. Six of the first 18 flights did not complete their missions successfully. 

However, the same rocket has played a significant part in India's efforts to develop the ability to launch larger satellites.

At the heart of this voyage is the indigenous cryogenic engine. During the 1990s, India requested cryogenic technology from Russia, but the US strongly opposed the transfer due to fears about missile proliferation. International regulations eventually stopped India from obtaining the technology it desired.

ISRO subsequently tackled the significantly more difficult challenge of developing the technology domestically.

Indian scientists had to perfect cryogenic propulsion systems that used liquid hydrogen and liquid oxygen at temperatures below minus 250 degrees Celsius. After years of development, testing, failures, and redesigns, India was finally able to create its own cryogenic upper stage.

That achievement marked a significant milestone in India's launch program and remains one of the defining technologies of the GSLV Mk II.

The rocket's capabilities have also been internationally validated. The GSLV Mk II was tasked with launching NISAR, the world's most costly civilian Earth imaging satellite, demonstrating confidence in the launcher's ability to perform hard missions. Friday's trip will be the nineteenth flight.

EOS-05: An eye that can keep watching India

The satellite riding aboard GSLV-F17 is critical to the mission's success.

EOS-05, also known as GISAT-1A, weighs about 2,367 kg and is intended to operate from geosynchronous orbit, roughly 36,000 kilometers above Earth. A geosynchronous satellite, as opposed to low-Earth orbit satellites, can maintain a continuous observation of the same large area.

This makes EOS-05 especially valuable where frequent monitoring is required. Its imagery is projected to be useful for disaster management, agricultural, and weather monitoring, as well as tracking changes across huge areas of India. Continuous observation is extremely useful during cyclones and other extreme weather occurrences, as well as for environmental and infrastructure monitoring. 

The satellite will not instantly move into its ultimate operational location. GSLV-F17 will first inject it into a Sub-Geosynchronous Transfer Orbit, after which EOS-05 will maneuver to its intended location.

The rocket is 51.7 meters tall and has a liftoff mass of 420.5 tons. Its three-stage design includes a solid core motor with four liquid-fuel strap-on boosters in the first stage, liquid propulsion in the second, and an indigenous cryogenic upper stage in the third.

A second chance after the EOS-03 setback

The mission comes with a recall of a previous disappointment. In August 2021, ISRO launched EOS-03 aboard GSLV-F10, with the goal of providing capabilities equivalent to those planned for EOS-05. The launch started normally, however the indigenous cryogenic upper stage failed to ignite as expected. The mission was eventually lost.

Five years later, EOS-05 marks another attempt to establish this critical Earth monitoring capability from geosynchronous orbit.

The timing adds to the mission's weight. The PSLV-C61/EOS-09 mission in May 2025 was unsuccessful due to a motor pressure issue, while the PSLV-C62 mission on January 12, 2026 failed to deliver its 16 satellites into their intended orbits due to an abnormality in the rocket's third stage.

The PSLV remains suspended while further examinations and tests continue. That makes the early hours of September 4 a critical time for ISRO. A successful GSLV-F17 flight will place an advanced Earth observation satellite in its intended orbit while also demonstrating the dependability of a new launch vehicle at a time when India's space program is looking to recover momentum.

Dr V Narayanan, ISRO Chairman, also offered prayers at Tirumala prior of the GSLV-F17/EOS-05 launch. The rocket and satellite had already progressed closer to launch, with GSLV-F17 moving from the Vehicle Assembly Building to the Umbilical Tower at the Satish Dhawan Space Center on August 28, 2026.

With the countdown beginning, the focus has shifted to the launch pad. For ISRO, a successful flight would imply more than just another satellite entering space. It would provide a crucial new Earth observation capacity, boost confidence in the GSLV Mk II, and serve as a timely reminder of the organization's ability to recover from setbacks.

And, bizarrely, the rocket carrying that responsibility is known as ISRO's "naughty boy".