The 28-hour countdown for the launch of earth observation satellite HysISalong with 30 satellites from eight countries on board ISRO`s trusted workhorse PSLV-C43 began at 5.58 AM on Wednesday. The launch is scheduled at 9.58 am on Thursday from Satish Dhawan Space Centre (SDSC) SHAR at Sriharikota in Andhra Pradesh about 110 km from Chennai, said Indian Space Research Organisation (ISRO). "The countdown for the launch of PSLV-C43/HysIS mission started today at 05:58 hrs IST," it said. The space agency said fuel filling of a PS4 stage (fourth stage) has been completed. The Hyper Spectral Imaging Satellite (HysIS), an earth observation satellite developed by ISRO, is the primary satellite of the PSLV-C43 mission. The mass of the spacecraft is about 380 kg, the space agency said adding that the satellite would be placed in 636 km-polar sun-synchronous orbits with an inclination of 97.957 degrees. The primary goal of HysIS, whose mission life is five years, is to study the earth`s surface invisible near infrared and shortwave infrared regions of the electromagnetic spectrum. The co-passengers of HysIS include 1 micro and 29 nanosatellites from eight different countries. All these satellites have been commercially contracted for launch through ISRO`s commercial arm Antrix Corporation Limited. All the satellites would be placed in a 504 km orbit by PSLV-C43, the space agency said PSLV is a four-stage launch vehicle with alternating solid and liquid stages. PSLV-C43, which is the 45th flight of the Polar Satellite Launch Vehicle (PSLV), is the `Core Alone` version of PSLV. It is the lightest version of the launch vehicle. This will be ISRO`s second launch in the month. The space agency had launched its latest communication satellite GSAT-29 on board GSLV MkIII-D2 on November 14.