PSLV-C52/ EOS-04 Mission


    In News

    • Recently, ISRO launched the EOS-04, an earth observation satellite, that is supposed to be the beginning of this year for the Indian space agency.

    What is EOS-04?

    • The 1,710-kg EOS-04, which will be placed in a sun synchronous polar orbit of 529 km, is a radar-imaging satellite which would have made it a part of the RISAT series earlier.
    • It is the fourth in a series of earth observation satellites that are being launched under a new generic name.
      • Two years ago, ISRO had moved to a new naming system for its earth observation satellites which till then had been named thematically, according to the purpose they were meant for.
    • EOS-04 was designed to provide high-quality images for applications such as agriculture, forestry and plantations, flood mapping, soil moisture and hydrology.
      • It will complement the data from Resourcesat, Cartosat and RISAT-2B series of satellites that are already in orbit.
      • It would replace the RISAT-1 which was launched in 2012 but has been non-functional for the last few years.
      • RISATs use synthetic aperture radars to produce high-resolution images of the land.
      • One big advantage that radar imaging has over optical instruments is that it is unaffected by weather, cloud or fog, or the lack of sunlight.
      • It can produce high-quality images in all conditions and at all times, making it suitable for surveillance.
    • The Cartosat series of satellites were meant to provide data for land topography and mapping, while the Oceansat satellites were meant for observations over sea.
    • Some INSAT-series, Resourcesat series, GISAT, Scatsat, and a few other earth observation satellites were named differently for the specific jobs they were assigned to do, or the different instruments that they.
    • All these would now become part of the new EOS series of satellites.
    • However, only the first of these newly named satellites, EOS-01, launched in 2020, is in orbit right now.
      • EOS-02, a micro-satellite to be flown on a new launch vehicle called SSLV (Small Satellite Launch Vehicle) is yet to be launched.
      • The launch of EOS-03 ended in a failure last year.


    • Land and forest mapping and monitoring, mapping of resources like water or minerals or fishes, weather and climate observations, soil assessment, and geospatial contour mapping are done through these satellites.

    Other Satellites

    • Two other small satellites INSPIREsat-1 and INS-2TD will be launched on the heaviest version of the PSLV rocket.
      • INSPIREsat-1 is a student satellite developed by the Thiruvananthapuram-based Indian Institute of Space Science and Technology in collaboration with the University of Colorado in the United States where it was assembled and tested.
        • This satellite will study the dynamics of the upper atmosphere and carries an X-ray spectrometer for studying solar flares.
      • INS-2TD, is a technology demonstrator for the first India-Bhutan joint satellite.
        • The two countries had signed a space agreement last year, and its first outcome would be the launch of BhutanSat, or INS-2B, on a PSLV rocket.
        • The INS-2TD has a thermal imaging camera meant for earth observation purposes, like assessment of land and water surface temperature, and identification of forest and tree cover.


    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 with 39 consecutively successful missions by June 2017.
    • The vehicle successfully launched two spacecraft – Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013 – that later traveled to Moon and Mars respectively.
    • 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.
    • It is the orbit most commonly used for satellite imaging, as being near the surface allows it to take images of higher resolution.
    • It is also the orbit used for the International Space Station (ISS), as it is easier for astronauts to travel to and from it at a shorter distance.

     Polar orbit and Sun-synchronous orbit (SSO):

    •  Satellites in polar orbits usually travel past Earth from north to south rather than from west to east, passing roughly over Earth’s poles.
    • Polar orbits are a type of low Earth orbit, as they are at low altitudes between 200 to 1000 km.
    • 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.

    Transfer orbits and geostationary transfer orbit (GTO):

    • Transfer orbits are a special kind of orbit used to get from one orbit to another.
    • Often, the satellites are instead placed on a transfer orbit: an orbit where, by using relatively little energy from built-in motors, the satellite or spacecraft can move from one orbit to another.

    Source: IE