Earth Observation Satellite-04, also called Radar Imagining Satellite has been designed to provide high-quality images under all weather conditions.
Breaking the jinx of 2021, which saw just one successful launch, Indian Space Research Organisation (ISRO) successfully launched the PSLV-C52 today from Sriharikota. The Polar Satellite Launch vehicle is carrying an Earth Observation Satellite (EOS-04) and two other satellites.
This is the beginning of a busy year for the Indian space agency. Earth Observation Satellite-04 is also called Radar Imagining Satellite (RISAT) that has been designed to provide high-quality images under all weather conditions.
The images will be for applications such as agriculture, forestry and plantations, flood mapping, soil moisture & hydrology. The spacecraft will collect observation data in C-Band completing the observations done by Resourcesat, Cartosat, and RISAt-2B series. The satellite has an operating life of a decade.
What is an Earth Observation Satellite?
This satellite is also known as the Earth remote sensing satellite or Radar Imagining Satellite (RISAT).
The Earth observation satellites are used or designed for Earth observation (EO) from orbit or space.
It includes spy satellites and those for non-military uses such as environmental monitoring, meteorology, cartography and others.
It helps to monitor and protect environment, manage resources, respond to humanitarian disasters, enable sustainable development.
They provide essential information on a vast number of areas, including ocean salinity, ice thickness, crop health and air quality.
The most common types are Earth-imaging satellites which take satellite images, analogous to aerial photographs.
Some EO satellites may perform remote sensing without forming pictures, such as in GNSS radio occultation.
Most EOS or remote sensing satellite operate at about 500 to 600 kilometres from the surface of the Earth.
Due to the substantial air drag they face at such a lower altitude, their orbits have to be rebooted frequently.
The first EOS was Sputnik 1, the first artificial satellite sent to Earth's orbit by the Soviet Union in 1957.
Sputnik 1 artificial satellite was used to study the topmost layer of Earth's atmosphere, the ionosphere.
The next year, the first American satellite called Explorer 1 was sent into space in January 1958.
Types of Earth observation satellites
EOS can be divided into two types based on how they capture imagery - passive and active.
Passive satellites detect radiation reflected off the Earth's surface, such as visible light and infrared.
In general, passive Earth observation satellites (EOS) are not able to work through clouds.
Active ones transmit energy towards Earth and measures returned signal which gives information about Earth's surface.
In general, active Earth observation satellites (EO) can see through the clouds.
How Earth observational satellites collect data?
Earth Observational Satellites travel on a range of different orbits, offering varying perspectives of the Earth.
Most EOS satellites do not continuously collect data due to limitations in power and memory.
Some offer regular and reliable data acquisition while others collect in small quantities over a period of time.
Data is stored on-board the satellite until it is in sight of a ground station to downlink the data.
The time between an image being taken and being available to download can range between a month to a few minutes.
As satellites are owned by different companies there are several data providers, each with their own pricing structure.
ISRO's Earth Observational Satellites
Indian Space Research Organisation (ISRO) has launched many operational remote sensing satellites.
Currently, thirteen operational satellites are in sun-synchronous orbit and four in Geostationary orbit.
The data from these satellites are used for several applications covering agriculture, water resources, urban planning.
It is also used for rural development, mineral prospecting, environment, forestry, ocean resources and disaster management.
How many operational satellites India has?
India currently has 53 operational satellites - 21 are Earth observation ones and 21 are communication-based.
Eight are navigation satellites, while the remaining three are science satellites.
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 "PSLVC52 blasted off carrying three satellites including EOS-04")
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