PSLV-C54 successfully places nine satellites in multiple orbits

Polar Satellite Launch Vehicle

• It is the third generation launch vehicle of India.
• It is the first Indian launch vehicle to be equipped with liquid stages.
• After its first successful launch in October 1994, PSLV emerged as the reliable and versatile workhorse launch vehicle of India.
• Difference: PSLV was developed to launch low-Earth Orbit satellites into polar and sun synchronous orbits whereas GSLV was developed to launch the heavier INSAT class of geosynchronous satellites into orbit.

Types of orbits

Geostationary orbit (GEO):

• Satellites in geostationary orbit (GEO) circle Earth above the equator from west to east following Earth’s rotation.
• This makes satellites in GEO appear to be ‘stationary’ over a fixed position.
• GEO is used by satellites that need to stay constantly above one particular place over Earth, such as telecommunication satellites.

 Low Earth orbit (LEO):

• A low Earth orbit (LEO) is an orbit that is relatively close to Earth’s surface. 
• It is normally at an altitude of less than 1000 km but could be as low as 160 km above Earth.
• Unlike satellites in GEO that must always orbit along Earth’s equator, LEO satellites do not always have to follow a particular path around Earth in the same way their plane can be tilted.

Polar orbit and Sun-synchronous orbit (SSO):

• Sun-synchronous orbit (SSO) is a particular kind of polar orbit. 
• Satellites in SSO, traveling over the Polar Regions, are synchronous with the Sun. 
  • This means they are synchronized to always be in the same ‘fixed’ position relative to the Sun.
• This means that the satellite will always observe a point on the Earth as if constantly at the same time of the day.