Chennai, Dec 14 (IANS): The 59-hour countdown for the launch of six Singaporean satellites by an Indian rocket is progressing smoothly at the rocket port in Sriharikota in Andhra Pradesh around 80km from here, said the Indian space agency.

According to Indian Space Research Organisation (ISRO), the countdown began at 7.00 a.m. on Monday.

The space agency's Mission Readiness Review committee and the Launch Authorisation Board gave the green signal for the December 16, 6.00 p.m. launch.

For ISRO this is going to be a fully commercial launch whereby it would earn an undisclosed sum of income by putting into orbit the six Singaporean satellites.

The satellites will be put into a 550 km circular orbit inclined at 15 degrees to the equator.

Out of the six satellites, the 400 kg earth observation satellite called TeLEOS-1 is the main passenger for the PSLV rocket and hence the mission is called TeLEOS mission by ISRO.

TeLEOS-1 is Singapore's first commercial earth observation satellite designed and developed by ST Electronics.

The other five co-passenger satellites are VELOX-C1 (123 kg), VELOX-II (13 kg), Kent Ridge-1 (78 kg), Galassia (3.4 kg) and Athenoxat-1.

On December 16, ISRO will be flying the 'core alone' variant of the PSLV rocket. The rocket will not have the strap on boosters, its standard feature

The successful launch of the six satellites will take ISRO's total flights of foreign satellites to 57.

The December 16 mission will be the last rocket launch mission for ISRO in 2015.

So far in 2015, ISRO has launched 14 satellites (three Indian and 11 foreign) from its rocket port in Sriharikota. Thirteen satellites were launched with PSLV rocket and one communication satellite - GSAT-6-with geosynchronous satellite launch vehicle (GSLV).

Last month India also launched its communication satellite GSAT-15 using the Ariane rocket of the European space agency which takes the total number of satellite launches in 2015 to 21 (17 foreign, four Indian).