GS Paper - III

The Union Cabinet approved India’s first mission to Venus which ISRO aims to launch in March 2028. This is the country’s second interplanetary mission after the Mars Orbiter Mission launched in 2013. The Venus mission is meant to study the planet from an orbit around it.

Why is it important to study Venus?

• Venus is often called Earth’s twin because it is similar in mass, density, and size.
• Therefore, studying Venus may offer scientists clues about the evolution of Earth. Notably, Venus is thought to have had water at some point in its history but has now become a dry and dusty planet.
• The mission will carry scientific instruments from India and abroad to examine the surface and sub-surface of Venus, its atmosphere, its ionosphere, and its interaction with the Sun.

The planet differs from Earth

• First, it has an extremely high surface temperature of around 462 degree Celsius, even hotter than Mercury — the planet that is closest to the Sun.
• Second, the atmospheric pressure on Venus is much higher than on Earth. It is almost similar to the pressure felt underneath the oceans on Earth.
• Third, 96.5% of the atmosphere of Venus is made up of carbon dioxide and there are sulphuric acid clouds on the planet.
• Fourth, Venus rotates very slowly on its axis as compared to Earth. One rotation of Venus lasts around 243 Earth days.

What do we know about the Venus mission?

• With Earth and Venus coming close to each other — offering the shortest path for a mission — only every 19 months, the timeline is of extreme importance.
• The mission was earlier planned for 2023 but as per the recent Cabinet, approvals will now take place in March 2028.
• The mission will carry scientific payloads weighing around 100 kg. It will follow a plan similar to India’s other space exploration missions — the satellite will gain speed in Earth’s orbit, will get sling-shot towards Venus, and then get captured in its orbit.
• Once the satellite exits the Earth orbit, it will take around 140 days to reach Venus. The mission will also see India perform aero-braking for the first time.

What is aero-braking?

• Keeping in mind the fuel considerations, the satellite would be placed in a highly elliptical orbit of 500 km x 60,000 km around Venus. This, however, is too high for the science payloads to conduct experiments.
• The satellite will be brought down to either 300 x 300 km or 200 x 600 km orbit — depending on the requirements of the finalised payload — with the help of aero-braking.
• This will see the satellite being pushed down to around 140 km several times when it is at the point in the elliptical orbit where it is closest to Venus.
• At this height, the satellite will skim through the outer layer of the Venusian atmosphere, which will create a drag slowing down the satellite and thereby reducing the height of the orbit gradually.
• The height range at which the satellite skims the atmosphere has to be selected very carefully — if the satellite plunges too deep, it may face extreme friction and burn up, but if it is too shallow, it may take a very long time for the satellite to reach the desired orbit.
• It will take around six months for the satellite to reach the intended orbit, as per discussions of scientists during the Venus science meet in 2022.
• Once the intended orbit is reached, however, the satellite will completely exit the planet’s atmosphere.
• This is because if the satellite continues to experience the drag, it will have to use up a lot of fuel to prevent the orbit from reducing further.

Are other countries also trying to study the planet?

• There have been several missions to Venus in the past by the United States, the erstwhile USSR, Japan, and a collaborative mission of the European Space Agency (ESA) with Japan.
• The US has planned at least two more missions to Venus in the future — DaVinci in 2029 and Veritas in 2031 — and the ESA has planned the EnVision mission for 2030.