India's solar mission will study the Sun's outermost layers — the corona and the chromosphere — and collect data about coronal mass ejection

After a seven year long wait, Aditya, India’s first dedicated scientific mission to study the sun is likely to get a go-ahead from the Prime Minister’s Office (PMO) this week. The ambitious solar mission will study the sun’s outer most layers, the corona and the chromosphere, collect data about coronal mass ejection and more, which will also yield information for space weather prediction.

The project costs approximately Rs 400 crores and is a joint venture between ISRO and physicists from Indian Institute of Astrophysics, Bengaluru; Inter University Centre for Astronomy and Astrophysics, Pune; Tata Institute of Fundamental Research, Mumbai, and other institutes.

Shubashree Desikan Shubashree Desikan

Though the project was conceptualised in 2008 itself, it has since morphed and grown and is now awaiting clearance with the government. It now aims to put a heavy satellite into what is called a halo orbit around the L1 point between the Sun and the Earth. This point is at a distance of about 1.5 million km from the earth. With the excitement about the Mars Orbiter Mission yet to settle down, this could be the next most complicated feat that ISRO has carried out till date.

In a three-body problem such as this – with the earth and sun engaged in an elliptical orbit and a relatively very light, call it massless in comparison, satellite being placed in between – there are five so-called lagrangian points in space where the light, third body — in our case, the satellite — may be placed so that it can maintain its position with respect to the two others. One of these is the L1 point, which is about 1.5 million km from the earth.

A halo orbit would be a circular orbit around the L1 point. The satellite will have to use its own power (spend energy) to remain in position within in this orbit without losing its way. Such orbits have not been attempted too often.

Studying the corona

Among the suite of instruments in the payload would be a solar coronagraph. “A combination of imaging and spectroscopy in multi-wavelength will enhance our understanding of the solar atmosphere. It will provide high time cadence sharp images of the solar chromosphere and the corona in the emission lines. These images will be used to study the highly dynamic nature of the solar corona including the small-scale coronal loops and large-scale Coronal Mass Ejections,” said Dipankar Banerjee, physicist from IIA, who is part of this project. The corona is the outermost layer of the Sun and the chromosphere is the second inner layer. Data such as this can help us understand the corona and solar wind, which is a spewing of charged particles into space, at speeds as high as 900 km/s and at about 1 million degrees Celsius temperature, affecting the environment there.

Just like on earth, environment in space changes due to happenings in the sun, such as solar storms (flares). This is known as space weather. Dibyendu Nandi, Head of Center of Excellence in Space Sciences, IISER, Kolkata, describes it so: “Solar storms and space weather affect satellite operations. They may interfere with electronic circuitry of satellites and also, through enhanced drag (friction effects), impact satellite mission lifetimes. They also impact the positional accuracy of satellites and thus impact GPS navigational networks. Space weather also impacts telecommunications, satellite TV broadcasts which are dependent on satellite-based transmission.”

Dr Nandi works in building models that can predict space weather. Hopeful about Aditya’s contribution to this, he remarks “The data from Aditya mission will be immensely helpful in discriminating between different models for the origin of solar storms and also for constraining how the storms evolve and what path they take through the interplanetary space from the Sun to the Earth. The forecasting models we are building will therefore be complemented by the Aditya observations.”

At the moment, there are models and calculations made by NASA which Indian scientists use to maintain their satellites. Now, there is a possibility of Indians developing their own space weather prediction models.

shubashree.desikan@thehindu.co.in