The countdown for ISRO’s (Indian Space reserach Organization) GSLV F12/NVS-01 launch mission commenced at 7:12 am Sunday, ahead of the lift-off that is scheduled for 10:42 am Monday, WION has learnt. The countdown is the final phase prior to launch where the launch vehicle’s liquid and cryogenic fuels are filled and the final health checks of crucial systems are carried out.

The GSLV rocket that stands tall at the second launchpad at the Satish Dhawan Space Centre, Sriharikota, is meant to place a 2,332 kg navigation satellite NVS-01 into a Geosynchronous Transfer Orbit (GTO). The GTO is a temporary parking orbit, into which the satellite will be hurled by the rocket. There on, the satellite will independently use its onboard propulsion systems to perform orbit-raising manoeuvres and reach its intended orbit. 

This will be the Indian space agency ISRO’s fourth launch mission of the calendar year 2023. Thus far in 2023, ISRO has launched its smallest rocket SSLV, the most-flown workhorse rocket PSLV and the heaviest rocket LVM3. Monday’s launch will add the GSLV to the list – marking the launch of all four operational vehicles of ISRO in a short span of four months. 

NVS-01 is the first in the series of second-generation navigation satellites built by ISRO’s UR Rao Satellite Centre in Bengaluru. At present, India uses its Navigation with Indian Constellation (NavIC) series of satellites for civilian and defence navigation, positioning, and timing services in the Indian mainland and even 1500 km beyond India’s borders. 

“NVS series of satellites will sustain and augment the NavIC with enhanced features. This series incorporates L1 band signals additionally to widen the services. For the first time, an indigenous atomic clock will be flown in NVS-01,” ISRO said. 

While using satellite-based positioning and navigation services, our position (of the GPS receiver) is determined concerning its distance from multiple satellites. When such a calculation happens, the distance value is obtained by multiplying the time (taken for signal to travel) and the speed of the signal (almost similar to the speed of light). In such cases, (when large values are being multiplied) even a variation of a billionth of a second can lead to an inaccurate distance value(by a few meters or tens of meters). Hence it is necessary to have atomic clocks that can work for several years without even nanosecond-level errors in timekeeping. 

Earlier, the NavIC series of satellites were known as IRNSS (Indian Regional Navigation Satellite System). It provides two types of services- Standard Positioning Service (SPS) which is provided to all the users and Restricted Service (RS), which is an encrypted service provided only to the authorised users. According to ISRO, some of the applications of the IRNSS/NavIC system are terrestrial, aerial and marine navigation, disaster management, vehicle tracking and fleet management and precise timing. According to ISRO, NavIC SPS signals are interoperable with other global navigation satellite system (GNSS) signals such as – GPS, Glonass, Galileo, and BeiDou.

ISRO’s NavIC satellites

ISRO’s current series of eight NavIC satellites were placed in orbit in a phased manner between the years 2013 and 2018 using PSLV rockets. All satellites in the first-generation NavIC series weighed 1,425 kg and carried foreign-origin atomic clocks. All IRNSS/NavIC series satellites carried two types of payloads – navigation payload and ranging payload. 

The navigation payload transmits signals for the determination of position, velocity and time. Rubidium atomic clocks are part of the navigation payload of the satellite. The ranging payload of these satellites consists of a C-band transponder which facilitates accurate determination of the range of the satellite.