INSAT-3D Satellite on its way to Kourou (ISRO official page)
INSAT-3D Satellite on its way to Kourou.ISRO official page

India's advanced weather satellite INSAT-3D, which was launched successfully on 26 July, has reached an intermediate orbit. The satellite is inching closer to the 36,000 km high geostationary orbit, which is its final orbit.

The meteorological satellite, carrying advanced weather monitoring payloads, was launched by European launch vehicle Ariane-5 VA-214 in the early hours of Friday from Kourou, French Guiana.

After travelling for 32 minutes and 48 seconds, the satellite with a lift-off mass of 2060 kg was placed in an elliptical Geosynchronous Transfer Orbit (GTO) with a perigee (nearest point to earth) of 250 km and an apogee (farthest point to earth) of 35,923 km. As soon as it was injected into the GTO, the satellite's solar panel was deployed. The Indian Space Research Organisation's (ISRO) Master Control Facility (MCF) at Hassan, Karnataka, took over the control of the satellite. 

The MCF performed two orbit raising manoeuvres on INSAT-3D on 27-28 July by firing the satellite's Liquid Apogee Motor (LAM), which is on board the satellite. During the first orbit manoeuvre, INSAT-3D's LAM was fired for some 65 minutes after which the satellite's nearest point to Earth rose to 15,780 km and its farthest point was at 35,800 km. In the second orbit manoeuvre, LAM was fired for 24 minutes. As a result, the perigee further rose to 31,800 km while the apogee was at 35,795 km. The inclination of the satellite's orbit with respect to the equatorial plane has reduced further from 0.67 deg (achieved in the first orbit manoeuvre) to 0.02 deg during the second orbit manoeuvre, according to a press statement from ISRO. 

Two days after its successful launch, INSAT-3D has reached an intermediate orbit which is closer to the final orbit. A third orbit monoeuvre, which is scheduled for today (29 July), will further move the satellite near geostationary altitude of about 36,000 km.

INSAT-3D is an advanced weather satellite configured with improved imaging system and atmospheric sounder. India already has two satellites - KALPANA and INSAT-3A, operating in the geostationary orbit for the past ten years. While these two satellites have imaging systems, INSAT-3D has an improved imaging system as well as atmospheric sounding system, which provides measurements of vertical distribution of temperature, humidity and integrated ozone concentration from surface to the top of the atmosphere.

Besides these two, INSAT-3D also carries Data Relay Transponder (DRT) and Satellite Aided Search and Rescue (SAS & R) Transponder to provide meteorological as well as search and rescue services. [To find out more details about INSAT-3D, click here]