At 6.23 am on 29.1.2025, the 50.9 metre tall and weighing 420.7 ton Geosynchronous Satellite Launch Vehicle-F15 (GSLV-F15) is slated to blast off from the second launch pad carrying the 2,250 kg NVS-02 navigation satellite.
The countdown for India's historic 100th rocket launch to orbit a navigation satellite on Wednesday that began at 2.53 am on Tuesday is progressing smoothly at the rocket port in Sriharikota, Andhra Pradesh, said a senior official of the Indian space agency.
With this mission, the Indian Space Research Organisation (ISRO) will be filling up part of the void in India's navigation satellite constellation -- Navigation with Indian Constellation or NavIC or colloquially known as the Indian GPS.
At 6.23 am on 29.1.2025, the 50.9 metre tall and weighing 420.7 ton Geosynchronous Satellite Launch Vehicle-F15 (GSLV-F15) is slated to blast off from the second launch pad carrying the 2,250 kg NVS-02 navigation satellite.
Just over 19 minutes into the flight the satellite will be placed into a Geosynchronous Transfer Orbit (GTO) at an altitude of 322.93 km.
From there the satellite will be taken up further to Geostationary Orbit.
According to a senior ISRO official, the GSLV-F15 launch will be its 100th rocket launch from Sriharikota taking into account all its rockets other than sounding rockets -- Satellite Launch Vehicle-3 (SLV3-4 missions), Augmented Satellite Launch Vehicle (ASLV-4 missions), Polar Satellite Launch Vehicle (PSLV-62 missions), GSLV (16 missions), Launch Vehicle Mark 3 (LVM3 earlier GSLV-MkIII, 7 missions), Small Satellite Launch Vehicle (SSLV, 3 missions), Air Breathing Propulsion Project (ABPP) and Reusable Launch Vehicle - Technology Demonstrator (RLV-TD) and two sub-orbital rocket launches by two private companies.
The NVS-02 will be the replacement for Indian Regional Navigation Satellite System -- 1E (IRNSS-1E) satellite -- part of the first generation satellite series. The long winding IRNSS is the old name for NavIC.
The NavIC will provide accurate Position, Velocity/Navigation and Timing (PV/NT) services to users in India and to the region extending about 1,500 km beyond the country's land mass.
As of now NavIC provides two types of services, namely, Standard Positioning service (SPS) and Restricted Service (RS).
NavIC's SPS provides a position accuracy of better than 20 m and timing accuracy better than 40 ns (nano seconds) over the primary service area, ISRO said.
According to the Indian space agency, five second-generation NavIC satellites NVS-01/02/03/04/05 will augment NavIC's base layer constellation with enhanced features for ensuring continuity of services.
The NVS series of satellites incorporates L1 band signals additionally to widen the services.
The first of the second generation NavIC NVS-01 was orbited on May 29, 2023 by GSLV-F12 rocket.
One of the spin-off benefits of the IRNSS programme is the indigenous development of atomic clocks by India.
With the imported clocks failing in some of the IRNSS satellites, India decided to develop its own atomic clocks saving about Rs 3 crore (Rs 30 million) per satellite.
Each IRNSS satellite carried three atomic clocks.
For the first time, an indigenous atomic clock was flown on NVS-01.
The NVS-02 uses a combination of indigenous and procured atomic clocks for precise time estimation.
The NVS-02 satellite, ISRO said, is configured with navigation payload in L1 (primary frequency band used by satellite constellations), L5 (used for high precision services) and S (commonly used in satellites) bands in addition to ranging payload in C-band like its predecessor-NVS-01.
NVS-02 satellite was designed, developed and integrated at the ISRO's U R Satellite Centre with the support of other satellite-based work Centres.
The Indian space agency said the navigation satellite will be used for strategic applications, terrestrial, aerial, and maritime navigation, precision agriculture, geodetic surveying, fleet management, location-based services in mobile devices, orbit determination for satellites, Internet-of-Things (IoT) based applications, emergency services and timing services.
Many mobile chipsets have NavIC signals now with the advent of L1 signal in the second generation Indian satellites.
The L1 signals offer better location based services in the consumer segment.
Out of the seven IRNSS satellites that were orbited earlier, four are functional providing Position, Navigation and Timing (PNT) service and the remaining ones offer safety-of-life messaging services.
The full constellation of seven satellites is expected to be completed in the coming years, according to the government.
India is one of the select countries that have its own satellite navigation system.
While NavIC is a regional system, the GPS belonging to the US and Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS) belonging to Russia, BeiDou of China and the European Union's Galileo are global systems.
However, the performance of NavIC, as seen with a seven satellite constellation, is at par with the contemporary systems in the envisaged service area, the government said.
Venkatachari Jagannathan can be reached at venkatacharijagannathan@gmail.com
Feature Presentation: Ashish Narsale/Rediff.com
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