Isro begins countdown for 100th mission: GSLV-F15 to launch NavIC satellite

Tirupati:The Indian Space Research Organisation (Isro) has commenced the 27-hour countdown for its landmark 100th mission at 2.53 am Tuesday.

The mission, involving the launch of the NVS-02 navigation satellite aboard the Geosynchronous Satellite Launch Vehicle (GSLV-F15), is scheduled for lift-off at 6.23 am Wednesday from the second launch pad at the Satish Dhawan Space Centre (SDSC-SHAR).

This mission is significant for multiple reasons, including that this is the 100th launch from India’s premier spaceport and the first under the leadership of Isro chairman V. Narayanan, who assumed office on January 13.

This mission also marks the 17th flight of the GSLV and the 11th flight equipped with an indigenously developed cryogenic upper stage.

GSLV-F15 aims to deploy the NVS-02 satellite, part of the second-generation Navigation with Indian Constellation (NavIC) series, into a geosynchronous orbit. This will replace the aging IRNSS-1E at 111.75°E longitude, bolstering the accuracy and coverage of NavIC, India’s independent regional navigation satellite system.

Standing 50.9 metres tall, GSLV-F15 is a three-stage vehicle with a lift-off mass of 420.7 tonnes. Its configuration features a solid core booster in the first stage, supplemented by four liquid strap-ons.

The second stage employs a high-thrust liquid engine, while the third stage consists of the indigenous cryogenic upper stage, powered by liquid hydrogen and liquid oxygen. The payload fairing is a metallic structure with a diameter of 3.4 metres, optimised for accommodating the 2,250 kg NVS-02 satellite.

According to Isro, the launch sequence of GSLV-F15 is planned carefully to ensure the successful deployment of the NVS-02 satellite into a geosynchronous transfer orbit. The mission begins with the ignition of the four L40H liquid strap-ons at T-minus 4.8 seconds, followed by the ignition of the solid core stage at lift-off. The strap-ons burn for 149 seconds before shutting off; and the first stage separates at 151.2 seconds.

Immediately after the first stage separation, the high-thrust liquid engine of the second stage ignites, propelling the vehicle further. The payload fairing separates at 237.42 seconds, at an altitude of 115km, reducing unnecessary mass as the vehicle exits the atmosphere.

The second stage burns until 291.16 seconds, achieving a velocity of 4,732 m/s, after which it separates, and the cryogenic upper stage ignites at 295.68 seconds.

The cryogenic stage operates for over 14 minutes, providing precise thrust to place the satellite in orbit. At 1,150.38 seconds after lift-off, the NVS-02 satellite separates from the vehicle at an altitude of 322.93km. The satellite is inserted into a GTO with a perigee of 170 km, an apogee of 36,577 km, and an inclination of 20.79° ± 0.1°.

The NVS-02 satellite is designed to provide enhanced Position, Velocity, and Timing services to users across India and up to 1,500km beyond its borders. NavIC offers two types of services: the Standard Positioning Service for civilian applications and the Restricted Service for strategic and military use. The satellite is set to bolster NavIC’s application spectrum, which includes defense operations, terrestrial, aerial, and maritime navigation, precision agriculture, fleet management, geodetic surveys, emergency response systems, and Internet-of-Things-based solutions.

Ahead of the launch, Narayanan, accompanied by a team of scientists, visited the Lord Venkateswara temple in Tirumala to offer prayers for the mission’s success. Narayanan highlighted the government’s allocation of `400 crore for the construction of a third launch pad at SDSC-SHAR.

Infographics:

Flight Profile: GSLV-F15 Mission

Lift-Off and Initial Stage Ignition:

- The mission begins with the ignition of the four liquid strap-ons (L40H) at -4.8 seconds, providing the initial thrust for the vehicle.

- The core solid booster (S139) ignites at T=0, lifting the vehicle off the Second Launch Pad at the SDSC-SHAR.

First Stage Burnout and Separation:

-The L40H strap-ons shut off at 149 seconds into the flight.

-Shortly after, at 151.2 seconds, the first stage (S139) separates from the vehicle.

Second Stage Ignition and Performance:

-The high-thrust liquid engine of the second stage (GS2) ignites immediately after the first stage separates.

-This stage continues to propel the vehicle further into space, reaching a velocity of approximately 3,436 m/s at 237.42 seconds.

Payload Fairing (PLF) Separation:

-At 237.42 seconds, the payload fairing (3.4-meter diameter metallic structure) separates at an altitude of 115 km, as the vehicle exits the dense atmospheric region, reducing unnecessary mass.

Second Stage Separation:

-The second stage shuts off at 291.16 seconds, reaching a velocity of approximately 4,732 m/s.

-The second stage separates at 294.68 seconds, and the cryogenic upper stage (CUS15) ignites at 295.68 seconds to take over the mission.

Cryogenic Upper Stage Operation:

-The indigenous cryogenic upper stage provides the precise thrust required to insert the satellite into a Geosynchronous Transfer Orbit.

-This stage burns for over 14 minutes, reaching a final velocity of approximately 9,693 m/s.

Satellite Deployment:

-The NVS-02 satellite separates from the vehicle at 1,150.38 seconds (19 minutes, 10 seconds) after lift-off, at an altitude of 322.93 km.

-The satellite is placed in a Geosynchronous Transfer Orbit with a perigee of 170 km, an apogee of 36,577 km, and an inclination of 20.79° ± 0.1°.

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GSLV-F15 Vehicle Characteristics

- Vehicle Height: 50.9 meters.

- Lift-off Mass: 420.7 tonnes.

- Payload Fairing (PLF): Metallic structure with a diameter of 3.4 meters.

- Stages Configuration:

- First Stage (GS1): Solid rocket motor (S139) with four liquid strap-ons (L40H).

- Second Stage (GS2): High-thrust liquid stage (GL40HT) powered by UH25 and N2O4.

- Third Stage (GS3): Indigenous Cryogenic Upper Stage (CUS15) using liquid hydrogen (LH2) and liquid oxygen (LOX).

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GSLV-F15 Mission Specifications

- Mission Purpose: To place the NVS-02 satellite into a Geosynchronous Transfer Orbit (GTO).

- Orbit Details:

- Perigee: 170 km.

- Apogee: 36,577 km.

- Inclination: 20.79° ± 0.1°.

- Payload Mass: 2,250 kg.

- Launch Azimuth: 106°.

- Flight Duration: 1,150.38 seconds (approximately 19 minutes and 10 seconds).