In a step towards self-reliance, India’s indigenously-developed global positioning system, called NavIC, will synchronise its clocks to time provided by the National Physical Laboratory, a Council of Scientific and Industrial Research body. Until now, the satellites on NavIC — managed by the Indian Space Research Organisation — relied on the United State’s GPS to ensure that the clocks aboard were working at the high-precision required in satellite-based communication.
A memorandum was signed between the CSIR and ISRO on Thursday to initiate this activity that will now require NPL to upgrade its time-keeping infrastructure and ISRO to make changes that will make NPL-provided time the default time source aboard the seven-satellite constellation.
Atomic clocks aboard NavIC, more formally called the Indian Regional Navigation Satellite System (IRNSS), are foreign-made and ISRO’s forthcoming satellite, IRNSS-1H, will continue using the same clocks. This satellite is being launched as a replacement for one of the seven satellites, IRNSS-1A, which has had problems with the accuracy of its clocks. “This is a step to eventually solely rely on India-provided time. We were waiting for a satellite constellation like NavIC to be able to completely start using NPL-provided time,” said V.V. Srinivasan, Director, SRO Telemetry, Tracking and Command Network (ISTRAC). “Earlier we had to trace the accuracy of time to international agencies such as US Naval Office.” Using Indian services would mean a more secure system and greater reliability, he added.
NavIC is designed to provide accurate position information service to users in India as well as the region extending up to 1500 km from its boundary, which is its primary service area.
The National Physical Laboratory (NPL), part of the Council of Scientific & Industrial Research, is host of the most accurate clocks in the country, and the only agency in India authorised to maintain Indian Standard Time (IST). The NPL maintains accuracy of ±20 nanoseconds through the Primary Time Scale, an ensemble of five caesium clocks and one hydrogen maser. The rest of the world connects to these via tele-clocks, satellite links, and Network Time Protocol services (which, for example, reflect in laptop clocks).