The 48 hour countdown for the launch of the rocket PSLV-C31 begins this morning at Sriharikota. The senior scientists of the Indian Space Research Organization, ISRO gave their approval for the countdown to begin at 9-hours-31 minutes today after a thorough review of the preparedness at the spaceport. The rocket will carry the Indian Regional Navigation Satellite Systems, IRNSS-1E at the same time on Wednesday. <br/><br/>It is the fifth in the series of seven satellites meant for navigation system. AIR correspondent reports, the system will be the Indian equivalent of the Global Positioning System GPS and provide road, air and maritime navigation services over a vast area when all the seven satellites are made operational. <br/><br/>The PSLV-C31 will be the first mission to be undertaken by ISRO this year. Its passenger IRNSS-1E will be complementing the four other satellites of its class that are already in operation in space. The ISRO has said two more satellites under the system would be made functional by the end of March this year. <br/><br/>With the earlier four satellites in space, standard positioning information of moving and non-moving objects are being gathered for 18 hours a day with the accuracy of 20 meters. ISRO says, when the other two satellites are also readied, it will be a non-stop flow of data with still better accuracy over a very large area.