Aditya-L1 mission to help India protect space assets: Ex-ISRO programme director

Rao says the spacecraft will collect data on the photosphere, chromosphere and the corona layer of the Sun using specialised detectors

While the  Indian Space Research Organisation (ISRO) launched the Aditya-L1 mission to study the sun, just days after the country made history by becoming the first to land near the Moon's south pole,  Moneycontrol talked to Dr Mukund Rao, former Programme Director at ISRO, to understand key matters related to the solar mission. Read here

Excerpts from the interview:

Why does Aditya matter to India as a nation?

The Aditya L1 mission will not only benefit the nation with advanced knowledge of solar activities and sun structure but also help in efforts to protect space assets. It is important that Indian space capability be at forefront so that we can be a part of the very few nations that conduct advanced studies on Sun - and even contribute to defining those early-decisions, policies that humanity will take for Space activities in the international arena.

The Sun affects our lives in many more ways today - the solar radiations and particles that are emitted by it reach Earth and impact, like a forceful gust, the hundreds of satellites that we have put up in space (for services like communications, imaging, positioning, scientific missions etc). The charged and energy particles directly impact the satellite performance - many times rendering them unusable, suddenly. More energetic particles can even travel through the surface of the satellite and damage the instruments inside. Solar flares produce many highly energetic protons which can reach the Earth in 30 minutes. During a geomagnetic storm, the Earth's atmosphere gets heated and an increased drag on the satellites is felt. With this extra resistance, the spacecraft slows down and loses altitude. To compensate for such solar events, orbital manoeuvres need to be carried out for the satellite to re-adjust its orbit and altitude. Therefore, it is important to have knowledge of such sun events.

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It is  important to protect the satellites because the investments are too high in space and the loss or risks needs to be minimised or even avoided. Even on the ground, the solar radiations can have impact. We also use radio waves for communications - telephony, broadcasting TV, power grids, aviation, transportation, maritime etc where radio waves carry signals from/to satellites or a tower to the hand-device/TV/terminals - these waves travel in atmosphere and bounce off the ionosphere (part of our atmosphere). The ionosphere contains charged particles and during a geomagnetic storm they get disturbed - we can easily lose our radio signals and communications. These services are commercial and large investments are involved.

Why is Aditya being positioned at Lagrange points?

Sun is 150 million km away and has temperatures of 15 million degrees Celsius. Thus it is not possible to get anywhere near it. Currently. missions to Sun reach around 1.5 million km and observe from there.  However, to make observations and collect data of Sun, it is important to be "static" or be "stationary" for making the constant and systematic observations of the Sun.  This is where the ingenuity and knowledge of humans plays a role.

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There is a point between Sun and Earth where the gravitational force of the two masses precisely equals the centripetal force (or velocity) required for a small object to move with them/ thus, these points in space can be used by spacecraft to reduce fuel consumption needed to remain in position. These are Lagrange Points - where satellites sent there tend to stay put and appear to be "stationary" to Sun and Earth. While there are five Lagrange Points, the L1 point of the Earth-Sun system affords an uninterrupted view of the Sun.

How will Aditya-L1 study the Sun if it is located about 148.5 million kilometres from the star?

Aditya L1 carries seven payloads, directly viewing the Sun, and collecting data on the photosphere, chromosphere and the corona layer of the Sun using specialised detectors and devices to measure electromagnetic radiation, charged particles and magnetic fields. These specialised  instruments are designed to observe the solar atmosphere by looking at the Sun. There are also other instruments that will observe at the L1 point the intensity and characteristics of particles and fields - one could then model how these propagate in space and what would be the intensity as it reaches Earth.

Reaching the L1 point will take almost four months.  The mission will observe and collect various data for about five years in its mission life. Even communications to/from Aditya would require many minutes to be completed - because of the distances, and India has established Deep Space Networking capabilities to support these. Thus, very valuable and rich data of the Sun would be available to India from the mission and a greater understanding of the Sun would be possible. Read here

Why is the launch from Sriharikota?

Launch of satellites require launchpads. These are special and advanced facilities that can launch rockets in a safe manner and take care of its trajectory, guidance and control and successful injection. Such launch pads are available in very few nations - Indian being one of them. There is one launch facility in India - which has two launch pads (meaning two rockets can be launched from this facility; something akin to two runways in an airfield) - this facility is in Sriharikota and is called the Satish Dhawan Space Centre (SDSC; Satish Dhawan was one eminent, visionary Chairman of ISRO who built the foundations of Indian Space programme). This launch facility can successfully launch various types of satellite launchers - SLV, PSLV, GSLV and so on.