KOCHI: The countdown to Isro’s 46th flight of Polar Satellite Launch Vehicle (PSLV-C44) is set to begin for the launch of 'Microsat -R’, an imaging satellite from Sriharikota first launch pad, on Jan 24 at 11.37 pm. This launch is unique because the rocket's fourth stage will be re-used automatically to launch 'Kalamsat’ for scientific experiment. Following that, three more PSLV launches are slated before April.“Countdown to launch of PSLV-C44 mission begins on Wednesday at 7.37 pm for a launch set for Thursday at 11.30 pm. It is the first flight of PSLV-DL variant. This rocket’s fourth stage PS4 will be automatically re-used as a platform after the launch of DRDO’s imaging satellite Microsat-R in low earth orbit. The fourth stage will be moved to a higher circular orbit so as to establish an orbital platform for carrying out experiments,” Vikram Sarabhai Space Centre (VSSC) director S Somnath told TOI. The indigenous lithium-ion technology is crucial to keep the fourth stage live for re-use, he said.Liquid Propulsion Systems Centre (LPSC) director V Narayanan said PSLV is a four-stage launch vehicle with alternating solid and liquid stages. PSLV-C44 is the first mission of PSLV-DL and is a new variant of PSLV with two strap-on configuration. He also confirmed that the countdown for PSLV-C44 mission begins at 7.37 pm on Wednesday for launch on Thursday night at 11.37 pm.Normally, after PSLV launch, its various stages of strap-ons is a waste that drops down into sea or ocean. In this rocket, the fourth stage will be automatically reused as a platform for the launch of a student experimental satellite in the name of Abdul Kalam to carry out scientific studies in another orbit, Isro scientists said. Called Kalamsat, this student payload developed by Chennai based organisation 'Space KIdz India’ will be the first to use PS4 as the orbital platform, the scientist said.In this, the fourth stage energy support is lithium ion technology, further in the next launch solar panels are planned to be used, the scientists said.On the next PSLV missions lined up, Isro scientists said, PSLV- C45 mission is planned before the first quarter of this year for the launch of advanced electronic intelligence satellite EMISAT with DRDO and 30 commercial satellites. PSLV- C46 is slated in February for the launch of the earth observation satellite Cartosat-3 with high-resolution cameras and optical devices for effective imaging. Then, PSLV-C47 mission planned in March is set for the launch of RISAT 2BR 1, a Radar Imaging Satellite for reconnaissance and strategic surveillance.