WHAT EXACTLY HAPPENED?
On 4 September 2026, ISRO launched the GSLV-F17 carrying EOS-05, an advanced Earth observation satellite.
The launch took place from:
- Satish Dhawan Space Centre (SDSC-SHAR)
- Sriharkota, Andhra Pradesh
- Second Launch Pad
- 2:55 AM IST
- Rocket: GSLV-F17
- Payload: EOS-05
- Satellite mass: approximately 2,367 kg
- Rocket height: 51.7 m
- Liftoff mass: approximately 420.5 tonnes
This was the 19th flight of India’s Geosynchronous Satellite Launch Vehicle (GSLV)
The launch occured during rainy conditions, but the vehicle successfully lifted off and EOS-05 separated from the launcher after reaching the intended transfer orbit.
Why is EOS-05 so important?
India’s first imaging satellite designed to operate from geosynchronous orbit.
ISRO describes EOS-05 as a state-of-the-art Earth-observation spacecraft and India’s first ever imaging satellite from geosynchronous orbit.
This is significant because the orbit determines how an Earth-observation satellite sees Earth.
Why is the orbit so important?
Imagine two photographers.
Photographer A- moving around the stadium
The photographer runs around the stadium and periodically looks at you.
He gets excellent close-up photographs, but
He isn’t looking at you continously.
This resembles may conventional Low Earth Orbit (LEO) Earth-observation satellites.
Photographer B- standing at a high vantage point
The school photographer stays in roughly the same position and continously watches the stadium.
The photograph may be taken from much farther away, but:
He can keep watching the same broad area.
This is broadly what a geostationary Earth-observation satellite provides.
Understanding the GSLV-F17 rocket
GSLV stands for:
Geosynchronous Satellite Launch Vehicle
GSLV-F17 is a three-stage launch vehicle.
The three stages are broadly:
Stage 1->Stage 2->Stage 3
with the third stage being the crucial cryogenic upper stage.
ISRO’s GSLV architecture uses:
- solid propulsion,
- liquid propulsion,
- cryogenic propulsion
Third stage-the cryogenic stage
This is perhaps the most technologically significant part of the GSLV.
The third stage uses an indigenous cryogenic upper stage, identified in the mission information as CUS-5.
It uses:
Liquid Hydrogen (LH2)
and
Liquid Oxygen (LOX)\
Cryogenic engines operate at extremely low temperatures because hydrogen and oxygen are stored in liquid form.
Why use cryogenic propulsion?
Because hydrogen has a very high specific impulse, making it highly effective for the upper stages of launch vehicles.
That is especially useful when you need to deliver a substantial payload to high-energy orbits.
Why is GSLV important when India already has LVM3?
India has multiple launch vehicles because they serve different payload/orbit requirements.
PSLV
Best known as India’s highly versatile workhorse.
Particularly useful for:
- polar orbits,
- Sun-synchronous orbits,
- Earth observation satellites
GSLV
Designed particularly for:
- heavier satellites
- geosynchronous transfer-type missions,
- communication/navigation/other high energy orbital missions
- heavier spacecraft
- human spaceflight ambitions,
- Gaganayan
Why was this launch psychologically important for ISRO?
Very well explained
This blog was really informative and interesting to read. It gave me a clear understanding of the successful launch of the EOS-05 satellite and ISRO’s achievement in space technology. I learned a lot from this post. Thank you for sharing such useful information!
Great article! Very informative and easy to understand. Thanks for sharing such useful information.