Observing the Earth – Journey of Indian Earth observation satellites from Bhaskara to EOS

 

From the humble start from Bhaskara I to EOS-1, the Indian Earth observation satellite technology has advanced significantly. Earlier, the technology required by the Indian satellite system was imported from foreign nations, however with time state of the art technology has been developed indigenously. In this short journey, there has been remarkable advancement of technology in the earth observation satellite in resolution, sensor technology, application areas, coverage etc.

Experimental stage - The beginning of the Indian earth observation satellite journey started with experimental satellites like Bhaskara I in 1979 followed by Rohini RS-D1, Bhaskara II and Rohini RS -D2. These had limited capabilities in terms of sensor and resolution.

IRS series - In 1988, Indian Space Research Organization launched the first indigenous operational remote sensing satellite in the IRS series, i.e  IRS – 1A. After this came the many satellites in IRS series i.e. 1A, 1B, 1E, P2,1C, P3, 1D, P4 and P6, each with improved capabilities than the previous one. IRS- P6 (which was continued as Resourcesat), launched in 2003, employed advanced multi-spectral LISS IV, LISS III and AWiFS sensor. The latest in this series is Resourcesat 2-A, launched in 2016, with much improved technology.

Oceansat series – The IRS – P4 satellite, launched in 1991, specifically for ocean applications was first one in the Oceansat series. The second satellite in this series is Oceansat -2 launched in 2009 with Ocean Colour Monitor-2 (OCM-2), Scatterometer and Radio Occultation Sounder for Atmospheric (ROSA) sensors.  SCASAT – 1 is the continuing mission for Oceansat series with wind scatterometer sensor. The third one in this series Oceansat -3 is expected to be launched in 2020.

Cartosat series –The first satellite, Cartosat - I was launched in 2005 with resolution of 2.5 meters. Then came Cartosat 2 in 2007, 2A in 2008 and 2B in 2010, 2C in 2016, 2D and 2E in 2017, 2F in 2018 and the latest one is Cartosat 3 in 2019. The imaging capability of each is better than the last one. The latest in the series, i.e. Cartosat – 3 can produce scene specific spot image with high resolution of 0.25 meters.

RISAT series – India entered into radar imaging through RISAT – 2 satellite in 2009. The second in the series, RISAT – 1, was delayed and launched 2012. The next in the series was RISAT – 2B and 2BR -1 in 2019 and the latest one in the series is EOS-1 launched in 2020.

INSAT series – INSAT series satellites are advanced meteorological satellites There are two satellite in this series i.e. INSAT – 3D launched in 2013 and INSAT – 3DR launched in 2016.

Other than these, there are few individual special earth observation satellites were launched for specific purposes.

Technology experiment satellite (TES) - Experimental high resolution Technology experiment satellite (TES) launched in 2001.

Megha torpiques- An indo-french satellite mission launched in 2011.

SARAL (Satellite with ARgos and ALtiKa)- Another Indo – France collaboration mission, launched in 2013

HysIS - Hyperspectral imaging satellite launched in 2018.

The Indian earth observation satellite journey is not finished here but has just started. The present observation satellite system with high resolution multi-spectral remote sensing data is delivering data which is not only an asset for the scientific community but also for development of the nation.

 

Reference - 

ISRO website, Department of Space, Indian Space Research Organization, https://www.isro.gov.in/about-isro

Image source - Free-Photos from Pixabay

 

 

Earth’s atmosphere – From a hot cloud of dust and gas to life nurturing environment

 

The early atmosphere –

History of earth – 4.6 billion years. 

Evidences - Oldest occurring rock – Faux Amphibolites of the Nuvvuagittuq greenstone belt - found in Quebec Canada with age of 4.28 billion years. Isotopic analysis of meteorites, soil, rock samples of moon.

Faux Ambibolites (Nuvvuagittuq Greenstone Belt, Eoarchean, 4.28 Ga; western Ungava Peninsula, eastern side of Hudson Bay, Quebec, Canada) James St. John, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons

 The continuous collisions between primordial solar nebula particles (interstellar gas and dust) is mainly considered responsible for the most rudimentary form of earth. This continued for some 150 million years until eventually clumped into a rock form. The mass of earth had very high temperature due to terrestrial accretion heat generated through –

o   Decay of radioactive isotopes

o   Gravitational energy of sinking metals

o   Impact of small planetary bodies bombarding into earth.

 ·         Eventually, rock material started melting bringing about sinking of heavier material rich in iron and nickel, to core and rising of lighter elements to top. The maximum amount of lighter primordial gases like hydrogen and helium escaped during this phase.

 ·      The light molten material crystallized to build initial thin crust. This thin and unstable crust collapsed again formed many times to ultimately form a thicker crust as a result of large scale convection current inside earth. At the same time, outgassing of gases from surface volcanic activity led to oceanic evolution and secondary atmosphere.

Oceanic evolution -

H2O particles were already present in the Earth mass during the planetary accretion phase of formation of earth. During outgassing temporary steam atmosphere was created which precipitated during the subsequent cooling phases of the earth.

Secondary atmosphere –

·         Volcanism was the major route through which degassing of volatile material from the inner Earth took place. Volcanic activity produces water vapor, Carbon dioxide, Carbon monoxide methane gas, nitrogen in substantial quantities but no oxygen.

Decrease in CO2 –

·         Carbon dioxide was the main gas providing heat in the early atmosphere as the early solar system was illuminated by a weak, young Sun that only delivered ∼75% of the present day energy.

According to a climate model, at 2.75 Ga, CO2 level was 500 times present atmospheric levels. However, by the Cambrian, CO2 levels were close to present atmospheric levels.

The main reason for the extraction of CO2 out of the atmosphere was the development of life forms in the ocean that seized carbon in organic and later inorganic (calcium carbonate) forms and buried it in sedimentary formations on the sea floor.

Evidence -  presence of early carbonated sediments,

        Increase in O2 –

·         The secondary atmosphere formed by outgassing was anoxygenic. Amount of oxygen in the atmosphere increased gradually through

• Solar radiation - UV rays break H2O into hydrogen and oxygen
• Organic photosynthesis by earliest form of life - Blue-green algae (Cyanobacteria) uses CO2 and H2O for photosynthesis and release free oxygen.

 ·         Oxygen production continued for 2.2 billion years and did not achieve considerable levels until 2 Ga and only approached present-day levels by 1.5 Ga. Due to chemical action with the material deposited through lava eruptions, such as iron and evaporite formations.

Evidence - Iron rock formation in earliest sediments at Isua in western Greenland aged 3.8 billion years ago. Barite gypsum bearing evaporite found in Pilbara region of western Australia. 3.5 billion years ago.

·         O2 level rose in atmosphere occurred with decrease in the iron deposition.

Evidence – Earliest form of life i.e. Eukaryotes which were present 1.4 billion years ago, require O2 content of about 0.02 present atmospheric level. Similarly, soft life forms like jelly fish, worms developed about 650 million years ago, which require the minimum oxygen level of 0.1 present atmospheric level. Plants first appeared 400 million years ago.

·         The evolution of more complex form of plants and animals extract more CO2 from the atmosphere and provide an additional source of O2.

·         Once O2 started to accumulate in the atmosphere, the production of ozone (O3) could occur, shielding the Earth’s surface from ultra violet (UV) radiation. 

 References –

• Neil C. Wells - The atmosphere and ocean: a physical introduction, 3rd Edition, Wiley Blackwell
• Essentials of Meteorology – An Invitation to the Atmosphere, Eighth Edition 2018, C. Donald Ahrens and Robert Henson, Cengage Learning.
• Brian Frederick Windley (2016) Geologic history of Earth, Encyclopædia Britannica. Available at https://www.britannica.com/science/geologic-history-of-Earth.  Accessed on November 23, 2020