ISRO's Polar Satellite Launch Vehicle, PSLV-C27, successfully launched the 1425 kg IRNSS-1D, the fourth satellite in the Indian Regional Navigation Satellite System (IRNSS) today evening (March 28, 2015) from Satish Dhawan Space Centre SHAR, Sriharikota. This is the twenty eighth consecutively successful mission of the PSLV. The 'XL' configuration of PSLV was used for this mission. Previously, the same configuration of the vehicle was successfully used seven times.

After the PSLV-C27 lift-off at 1719 hrs IST from the Second Launch Pad with the ignition of the first stage, the subsequent important flight events, namely, strap-on ignitions and separations, first stage
separation, second stage ignition, heat-shield separation, second stage separation, third stage ignition and separation, fourth stage ignition and satellite injection, took place as planned. After a flight of about 19 minutes 25 seconds, IRNSS-1D Satellite was injected to an elliptical orbit  of  282.52 km X 20,644 km (very close to the intended orbit) and successfully separated  from the PSLV fourth stage.
After injection, the solar panels of IRNSS-1D were deployed automatically. ISRO's Master Control Facility (at Hassan, Karnataka) took over the control of the satellite. In the coming days, four orbit manoeuvres will be conducted from Master Control Facility to position the satellite in the Geosynchronous Orbit at 111.75 deg East longitude with 30.5 deg inclination.

IRNSS-1D is the fourth of the seven satellites constituting the space segment of the Indian Regional Navigation Satellite System. IRNSS-1A, 1B and 1C, the first three satellites of the constellation, were successfully launched by PSLV on July 02, 2013, April 04, 2014 and October 16, 2014 respectively. All the three satellites are functioning satisfactorily from their designated orbital positions.
IRNSS is an independent regional navigation satellite system designed to provide position information in the Indian region and 1500 km around the Indian mainland. IRNSS would provide two types of services, namely, Standard Positioning Services (SPS) - provided to all users - and Restricted Services (RS), provided to authorised users.

A number of ground stations responsible for the generation and transmission of navigation parameters, satellite control, satellite ranging and monitoring, etc., have been established in many locations
across the country.

In the coming months, the next satellite of this constellation, namely,IRNSS-1E, is scheduled to be launched by PSLV. The entire IRNSS constellation of seven satellites is planned to be completed by 2016.