Learning a bit about GSLV-F17 EOS-05 Mission!

| August 30, 2026 | Amateur Radio (Ham Radio) | No Comments

Information is available at: https://www.isro.gov.in/media_isro/image/index/GSLVF17_EOS05/GSLV_F17_EOS_05_Mission_Brochure_29082026.pdf As there are several abbreviations terms which are new for me, I thought of understanding them for improving my general knowledge on Indian Space Program. EOS-05 is a state-of-the-art Earth observation spacecraft. It is India’s first ever imaging satellite from Geosynchronous orbit.

“GSLV-F17 is the 19th flight of India’s Geosynchronous Satellite Launch Vehicle (GSLV) and the configuration of GSLV-F17 Payload Fairing is 4 m dia ogive (composite) version. The GSLV-F17 vehicle will place EOS-05 satellite into a Sub-Geosynchronous Transfer Orbit (SubGTO). Launch is planned from the Second Launch Pad (SLP) at Satish Dhawan Space Centre, SHAR”

The 4-meter diameter ogive composite payload fairing is a nose cone structure used on ISRO’s Geosynchronous Satellite Launch Vehicle (GSLV) missions, such as the GSLV-F17/EOS-05 flight, to protect satellites from aerodynamic pressure, heat, and acoustic loads during atmospheric ascent.

Key Features

  • Dimensions: 4 meters in diameter with an ogive (curved nose cone) profile.
  • Material: Lightweight composite construction providing high stiffness and structural integrity.
  • Function: Shields the spacecraft from extreme thermal, acoustic, and mechanical stress during launch.

GSLV-F17 Vehicle Characteristics

Vehicle Height 51.7 m
Lift off Mass 420.5 t
Stages 3
First Stage (GS1:GSLV Stage 1) S139+4 L40H
Second Stage (GS2) GL40HT
Third Stage (GS3) CUS15

First Stage (GS1) — S139+4 L40H: This is the core stage consisting of a massive S139 solid rocket motor carrying 138 tonnes of hydroxyl-terminated polybutadiene (HTPB) propellant. It is augmented by four L40H liquid strap-on boosters powered by hypergolic-fueled Vikas engines to provide massive initial liftoff thrust. These have UH25 (75% Unsymmetrical Dimethylhydrazine + 25% Hydrazine Hydrate) as fuel and Nitrogen Tetroxide (N₂O₄) as oxidizer.
Second Stage (GS2) — GL40HT: A modified liquid propulsion stage utilizing an improved high-pressure Vikas engine configuration to sustain acceleration after the first stage separates. This stage also has UH25 (75% Unsymmetrical Dimethylhydrazine + 25% Hydrazine Hydrate) as fuel and Nitrogen Tetroxide (N₂O₄) as oxidizer.
Third Stage (GS3) — CUS15: This represents the indigenous Cryogenic Upper Stage loaded with approximately 15 tonnes of high-efficiency liquid hydrogen (LH2) fuel and liquid oxygen (LOX) oxidizer, engineered to precisely inject heavy satellite payloads into their final orbits.