Satellite Orbits and Overview of SLV, ASLV and PSLV

Satellite Orbits and Overview of SLV, ASLV and PSLV

Question: PSLV XL 28 was recently launched with 5 UK satellites, marking the heaviest commercial load carried by ISRO to date. Name the different kinds of satellite orbits and how these are placed in orbit. Also provide an overview of the SLV, ASLV, GLSV and PSLV projects of ISRO.

About Satellite Orbits

- There are three kinds of satellite orbits-low, medium and high.

- High earth/geosynchronous orbit is located at the height of 35,780 km from the earth’s surface

- Mid earth orbit is at the height of 2000 to 35,780 km

- Low earth orbit is located 180-2,000 km above the surface of the earth

- Geosynchronous satellite orbits earth at the same speed as the rotation of the planet on its axis thereby remaining in the same position in connection to earth

- These satellites are useful for communication(phones, TV, radio) as well as weather monitoring

- Scientific and remote sensing satellites are mostly in the low earth orbit

- Most commonly used low earth orbit is referred to as the polar orbit

- Satellites placed within this orbit move from pole to pole around the earth

- Polar orbit is sun synchronous indicating it passes a spot on the earth the precise time each day

- For example, a sun synchronised satellite can measure air quality of a given place at a specific time

- Launch vehicles are used to put satellites in their respective orbits.

- The first sounding rocket was launched from Indian soil on November 21, 1963

- India took 20 years to reach operational ability though it commenced with the development of launch vehicles in the early 1970s

SLV, ASLV, PSLV and GSLV

- Satellite Launch Vehicle/SLV was the first experimental launch vehicle of India capable of placing 40 kg payloads in low earth orbits

- Following initial failure in a 1979 launch, SLV-3 successfully launched Rohini or RS-1

- This made India the sixth country to possess capability of launching satellites

- Following the successful completion of the SLV programme, ISRO launched Augmented Satellite Launch Vehicle Programme

- This launch vehicle augmented the payload capacity to around 150 kg; this is thrice the times of SLV

- It was also used for the validation of critical technologies for future launch vehicles

- PSLV or Polar Satellite Launch Vehicle is the system used for launching low orbit satellites to sun synchronous polar orbits

- This is the next stage of the SLV and ASLV programmes

- It was used for launching IRS or Indian Remote Sensing Satellites

- Despite the success of the PSLV programme, India still does not possess the capability to launch INSAT type heavy communication satellites in geosynchronous orbit

- This capability will only be possible following development of cryogenic engines associated with liquified gas

- India’s GSLV or Geosynchronous Satellite Launch Vehicle programme commenced in the 1990s

- India successfully launched a GSLV using indigenous cryogenic technology in 2014

Facts and Stats

About PSLV

- The first developmental launch of PSLV took place in 1993

- The vehicle failed to put IRS-IE into orbit

- Vehicle became operational following the launch of IRS-ID in September 1996

- Since 1999, PSLV has launched over 45 satellites for 19 nations

- PSLV is also used for launching MOM and Chandrayaan-1