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SSLV-D1/EOS-2 Mission


The SSLV D1/EOS-2 mission was carrying two satellites — the Earth Observation Satellite-2 (EOS-2 and AzadiSAT. However, the mission failed to place the satellites in their required orbits, and the satellites, as they were already detached from the launch vehicle, were lost.


GS III- Science and Technology

Dimensions of the Article:

  1. What was the purpose of the SSLV-D1/EOS-2 mission?
  2. Which part of the mission succeeded and where did it fail?
  3. Difference between circular and elliptical orbits
  4. What are the launch vehicles used by ISRO?

What was the purpose of the SSLV-D1/EOS-2 mission?

  • The purpose of this mission was to place the two satellites in circular low-Earth orbits at a height of about 350 km above the Equator.
  • The mission aimed to place the EOS-2 in a circular low-Earth orbit at a height of about 350 km above the Equator and inclined at an angle of 37 degrees.

EOS-2 (135 kg):

  • It was designed and developed by ISRO, offered advanced optical remote sensing operations.
  • It would have operated in the infrared region and could have served many purposes, from imaging for climate studies to simply keeping an eye on Earth.

AzadiSAT (8 kg):

  • It was a collective of 75 tiny payloads weighing around 50 grams each, which were integrated by students.
  • It carried tiny experiments which would have measured the ionising radiation in its orbit and also a transponder which worked in the ham radio frequency to enable amateur operators to access it.

Which part of the mission succeeded and where did it fail?

  • The SSLV was composed of three stages powered by solid fuels and these three performed their function as planned.
  • However, when it came to the stage when the satellites had to be set in orbit, there was a glitch which resulted in the satellites being lost forever.
  • With a degree of openness that is unprecedented in ISRO, it was announced that there was a malfunctioning of a sensor which resulted in placing the satellites in an elliptical orbit, rather than a circular orbit.
  • The ellipse or oval shape of the elliptical orbit is elongated in one direction and compressed in another (the so-called major and minor axes, which are like two radii of the ellipse).
  • The shortest height above the Earth of this oval orbit was only about 76 km.

Difference between circular and elliptical orbits

  • Mostly objects such as satellites and spacecrafts are put in elliptical orbits only temporarily.
  • They are then either pushed up to circular orbits at a greater height or the acceleration is increased until the trajectory changes from an ellipse to a hyperbola and the spacecraft escapes the gravity of the Earth in order to move further into space — for example, to the Moon or Mars or further away.
  • Satellites that orbit the Earth are mostly placed in circular orbits.
  • One reason is that if the satellite is used for imaging the Earth, it is easier if it has a fixed distance from the Earth.
  • If the distance keeps changing as in an elliptical orbit, keeping the cameras focussed can become complicated.

Why do we need to develop an SSLV when we have successfully used PSLV and GSLV?

  • The PSLV (Polar Satellite Launch Vehicle) and GSLV (Geosynchronous Satellite Launch Vehicle) are quite powerful and can carry huge loads.
  • To place an Earth Orbiting Satellite in a low Earth orbit, one does not need such power horses.
  • The SSLV can easily carry small-to-medium loads from 10 kg to 500 kg.
  • It is less expensive.
  • The three stages being powered by solid fuel is another advantage.
  • Solid fuel is easier to handle, whereas handling the liquid propellants used in the PSLV and GSLV is more complex.

What are the launch vehicles used by ISRO?

Polar Satellite Launch Vehicle (PSLV):Since its initial launch in 1994, PSLV has served as ISRO’s primary rocket. However, compared to those deployed in the 1990s, today’s PSLV is significantly more advanced and powerful.

The PSLV is the most dependable rocket that ISRO has employed to date, with 52 of its 54 flights being successful.

It is the first Indian launch vehicle to be fitted with liquid stages.

It successfully launched two spacecraft that later travelled to the Moon and Mars, namely Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013.

There are numerous variations of the two launch vehicles that ISRO currently utilizes, the PSLV and GSLV (Geosynchronous Satellite Launch Vehicle).  
Geosynchronous Satellite Launch Vehicle (GSLV):The considerably more potent GSLV rocket is designed to lift heavier satellites farther into space. 18 missions have been completed by GSLV rockets to this point, four of them were unsuccessful.

Lowering earth orbits may require satellites weighing 10,000 kg.

The third stage of the GSLV Mk II is the indigenously developed Cryogenic Upper Stage (CUS), and the Mk-III variants have rendered ISRO completely self-sufficient for launching its satellites.

The European Arianne launch vehicle was previously utilised to carry its heavier satellites into orbit.  
Small Satellite Launch Vehicle (SSLV):SSLV is designed to provide affordable launch services for satellites up to 500 kg in response to the growing demand for small and micro-satellites around the world.

It is intended to launch the indigenous EOS-03 earth observation satellite into orbit.

-Source: The Hindu

November 2023