Date with Earth's twin

A mission to Venus is both challenging and rewarding

The Indian Space Research Organisation (Isro) recently called upon the academic community to design and submit proposals for scientific experiments for its planned Venus orbital mission. The mission, which will probably be called “Shukrayaan”, is an ambitious but logical follow-up to the moon missions, Chandrayaan I and II and the Mars Mission, Mangalyaan. Venus will ensure that Isro develops new capabilities. It could be a huge boost to the Indian astronomy and planetary science community. The mission could derive useful new data and key insights into the hot button issue of climate change. 

But a Venus probe presents very different problems compared to a Mars probe. Mars is further from the Sun, with an elliptical orbit that takes it around the Sun in 687 Earth-days. It was hard to reach, especially since Isro used its underpowered PSLV (Polar Satellite Launch Vehicle) rocket. Therefore, the Mars Orbital Mission had a tight launch window and Isro had to compute a complicated route. However, Mars is a cool, dry planet with a very thin atmosphere. Orbiting around the planet has presented relatively few problems.

In contrast, Venus is much closer to the Sun with an orbit of 225 Earth-days. Its size and gravity are also closer to those of Earth. As such, plotting a route is less problematic. But the last mile of getting into orbit and maintaining a functional orbiter will be challenging nevertheless. Moreover, Venus’ atmosphere is about 90 times as thick as Earth’s. The air pressure approaches levels encountered on Earth only at ocean depths of one km. There are hurricane force winds blowing at 350 kmph — imagine ocean currents travelling at that speed. The air in Venus contains vast amounts of sulphuric acid and other chemicals that corrode metals. The ambient temperature is about 450-degrees Centigrade. Isro’s engineers will have to use materials to withstand nightmarish heat and pressure gradients. Telemetry could be a challenge. The experiments will be hard to deploy as well.

But an investigation of Venus could be richly rewarding, offering useful insights to planetary scientists. For instance, its atmosphere contains lots of carbon dioxide and other greenhouse gases. This makes it the hottest planet and understanding the mechanism of greenhouse effects on Venus will help in our understanding of climate change. Probes of Venus started in the 1960s with the Soviet Venera missions and the US Mariner missions. There have been a couple of Japanese probes as well, including the ongoing Akatsuki mission. Yet, given the tough atmospheric conditions, much basic data is still missing. 

The proposed Isro mission could contribute a lot to our understanding of this odd neighbour. The experimental payload capability of the proposed satellite is likely to be 175 kg with 500 W of power. The proposed orbit is expected to be an ellipse of 500 x 60,000 km, which will be slowly reduced. One very positive sign is that Isro is interested in greater cooperation with the academic establishment in the country. It has already asked for experimental proposals. However, proposals have to be submitted by May 19, which is decidedly too short a timeframe. Once proposals are shortlisted, experimenters will receive a fair amount of time to work out the exact specifications. There is no set timeframe for this though. The mission can be launched earliest in 2020, or even later. 

There could be multiple positive fallouts befitting the perception of a supposedly benign influence that “Shukra” has according to our culture. Isro and the wider scientific community will learn a lot from this challenge. The close cooperation between Isro and the academic establishment could result in network effects and that would be a bonus.