NAVIC – AMBITIOUS PROJECT OF ISRO
We are not new to GPS systems as we use it for our day-to-day logistics purposes. But are we aware that GPS is owned by a foreign nation and what if they restrict its services suddenly. So, as an alternate to GPS, ISRO has launched Indian Regional Navigation Satellite System (IRNSS) which is officially termed as NaVIC. It was termed NaVIC which translates to Boatman in Hindi to honour the fishermen of our nation. It is functioning with the help of ANTRIX, the commercial wing.
During Kargil war (1999) India was deprived for access to the hostile situation in which no proper location sketch or positioning data was handed over to Indian Military. So India decided to have its own satellite and began developing for both civilian and military purpose.
NaVIC has two level of services namely a Standard Positioning Service(SPS) providing rough location which is used for civilian purpose and a Restricted Service(RS) more accurate tracking which is encrypted and mainly used for military purposes and authorized users. The accuracy of these systems is one metre (3ft 3”) which is provided for public use and is seen in the newly launched Snapdragon processors in Mobile phones. The restricted one which is encrypted has an accuracy of 0.1metres (3.9”) which is more accurate than a single GPS (30 centimetres).
Initially only L5 frequency band was used. But after the launch of all 7 satellites, two frequency bands L5 and S bands are used. This doesn’t imply that Google Maps will stop functioning. Only the tracking system changes from GPS to NaVIC. There are 7 satellites which adopt NaVIC and will provide positioning data for Indian territory up to a range of 1500km. The atomic clocks that are used in satellites requires a specific time for stabilization and then they are adjusted with the Indian Standard Time (IST). Global positioning system uses 24 satellites to collect data over the complete global area whereas NaVIC uses 7 satellites to collect data over Indian territory alone. Thus the accuracy level obtained can be increased with the help of NaVIC. ISRO has launched 9 satellites in total for implementation of NaVIC. IRNSS-1H was lost in the launch failure of PSLV – C39 on AUGUST 31, 2017 and was the eighth satellite and IRNSS-1A which was the first navigation satellite lost its usage as the Rubidium Atomic clocks attached with it failed.
GAGAN is a satellite based augmented system (SBAS) implemented jointly with Airport Authority of India (AAI). The main objectives of GAGAN are to provide satellite-based navigation services with accuracy and integrity required for civil aviation applications and to provide better air traffic management over Indian airspace. The system will be in alliance with other International SBAS systems and provide seamless navigation across regional boundaries. The GAGAN signal-in-space (SIS) is available through GSAT-8 and GSAT-10.
IRNSS system time is given as a 27 bit binary number composed of two parameters. The week number is an integer counter that gives the sequential week number from the origin of the IRNSS time. This parameter is coded on 10 bits appearing in the first subframe which covers 1024 weeks (about 19 years). The time of week count (TOWC) indicates the number of 12 second counts at which the next subframe will begin. It is represented in 17 bits. The TOWC value ranges from 1 – 50400 to cover one entire week. The time of week in seconds is obtained by multiplying TOWC with 12. TOWC will have a value of 1 at 00:00:00 Sunday (changeover from Saturday to Sunday).
The IRNSS system time starts shall be 00:00 Universal Time on Sunday August 22nd, 1999. At the start, IRNSS system time shall be ahead of Universal Time Coordinate by 13 leap seconds. The transmission timing of the navigation message provided through the TOWC is synchronized to IRNSS system time. IRNSS navigation system uses WGS 84 co-ordinate system for computing the user position. NaVIC will also play a vital role in the conflict between India and China border issue as any trespassing within our boundary can be monitored. Once NaVIC is launched completely over the entire nation, we will have full control of our territory and peace within Indian Territory can be established.