India's PSLV-C39 to launch  navigation satellite IRNSS-1H on Thurday evening
IRNSS-1H spacecraft integrated with PSLV-C39 at the Satish Dhawan Space Centre, at Sriharikota. Photo: ISRO

India's PSLV-C39 to launch navigation satellite IRNSS-1H on Thurday evening

New Delhi, August 31, 2017

India's workhorse Polar Satellite Launch Vehicle (PSLV-C39) is slated to take off with navigation satellite IRNSS-1H from the second launch pad of the Satish Dhawan Space Centre (SDSC) at Sriharikota in Andhra Pradesh this evening.
The launch is scheduled for 1900 hours today. The 29-hour countdown for the launch started at 1400 hours yesterday, Indian Space Research Organisation (ISRO) sources said.
As in the previous six launches of IRNSS satellites, PSLV-C39 will use ‘XL’ version of PSLV equipped with six strap-ons, each carrying 12 tons of propellant, they said.
This will be the 41st flight of the PSLV and it is amed at launching IRNSS-1H, the eighth satellite of the Indian Indian Regional Navigation Satellite System (IRNSS), into a Sub-Geosynchronous Transfer Orbit (Sub-GTO) with a 284 km perigee and 20,650 km apogee with an inclination of 19.2 degrees with respect to the equatorial plane. 
After injection into this preliminary orbit, the two solar panels of IRNSS-1H will be automatically deployed in quick succession and the Master Control Facility (MCF) at Hassan will take control of the satellite and perform the initial orbit raising manoeuvres using its Liquid Apogee Motor (LAM), thereby finally placing it in its designated slot in the inclined Geosynchronous orbit.
While IRNSS-1H joins the constellation for providing navigation services, IRNSS-1A will be used for messaging services. IRNSS 1H comes with more flexibility in service and it is compatible with the satellites which are in orbit, the sources said.
Like its other IRNSS predecessors, IRNSS-1H also carries two types of payloads – navigation payload and ranging payload. The navigation payload of IRNSS-1H will transmit navigation service signals to the users. This payload will be operating in L5-band and S-band. Highly accurate Rubidium atomic clocks are part of the navigation payload of the satellite. The ranging payload of IRNSS-1H consists of a C-band transponder, which facilitates accurate determination of the range of the satellite. IRNSS-1H also carries Corner Cube Retro Reflectors for laser ranging.
Besides the seven IRNSS satellites, PSLV-XL has also launched many other spacecraft, including India's Mars Orbiter spacecraft, the multi-wavelength observatory Astrosat, Radar Imaging Satellite RISAT-1 and communication satellite GSAT-12. The launch of 104 satellites during a single mission by PSLV in February 2017 was the most prominent of its recent successes, the sources said.
With the operationalisation of seven satellites in 2016, the performance of the independent regional navigation system over India was demonstrated for the targeted position accuracy, which is better than 20 metres over 24 hours of the day, ISRO said.
NavIC (Navigation with Indian Constellation) ground segment is responsible for navigation parameter generation and transmission, satellite control, ranging and integrity monitoring as well as time-keeping.
NavIC ground segment is operational 24x7. It has a number of Indian Range and Integrity Monitoring Stations (IRIMS), which are spread across the country. The ground segment also has IRNSS CDMA Ranging Stations, IRNSS Network Timing Centres, ISRO Navigation Centres and Spacecraft Control Facilities. All of these are interconnected through a robust data communication network.
NavIC has applications in the areas of fisheries, shipping, railways, resource management, location based services, survey and alignment and time synchronised services.
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