Aditya will shape the next phase of our space forays
The mission to the Sun will enrich our understanding of the solar corona and space weather. The data will be a shot in the arm for Indian researchers
In the last 10 days, the landscape of global space exploration has undergone a dramatic transformation. India pole-vaulted to the front row of space exploration, with the successful soft-landing on the southern polar region of the Moon. The precision and the frugal economics with which the mission was executed attracted the attention of not only the nation but also the world. Before we could take a breath and absorb this stupendous feat, the Indian Space Research Organisation (Isro) announced the launch of its next ambitious mission — the Aditya-L1. This is the first dedicated mission to study the Sun. For the first time, the Indian space mission is flying to the Sun-Earth L1 lagrange point (the point of equilibrium where a small-body object can stay put under the opposing gravitational pulls of two large-body objects), which is about 1.5 million km away.
In scientific missions, the first requirement is the definition of the outstanding science question at hand, followed by detailing the experiment that needs to be performed to answer the question, and finally, the design, fabrication and space qualification of the instrument. Let us look at the why, what and how of this mission.
The Sun is the star we live with, and there are several compelling questions that are unanswered about it, such as the mechanics of the heating of the solar corona (the outermost part of the Sun’s atmosphere), solar activity and space weather. The Sun is very dynamic on very small time scales such as minutes to very long time scales such as the 11-year-long cycle of its magnetic activity, which flips every decade. The mass ejections from the corona cause a lot of disturbance in space, resulting in damage to our space assets. These demand an unobstructed view of the Sun from a vantage point and 24/7 monitoring. The instruments on the Aditya-L1 mission, therefore, are designed to answer such scientific questions, including understanding space weather. When placed in an orbit around the Sun-Earth L1 lagrange point, the instruments will have an uninterrupted view of the Sun.
The Aditya-L1 mission is the upgraded version of a small foray with a coronagraph (which blocks out light emitted by the Sun’s actual surface, so that the corona can be observed), originally proposed about one-and-a-half decades ago. It was around the early 2010s when the mission objectives were enhanced, including the modification of the orbit to the Sun-Earth L1 lagrange point. Along with this, more scientific instruments from various Indian institutions were also included. The main objective was to continuously monitor the Sun and its activities, make measurements of the energetic phenomena that control the space weather, and sample the space environment near the L1 point that moves around the Sun along with the Earth.
With ever increasing dependency on space technology, our assets in space are soaring. The electronics on board need to perform without failure to carry out mission operations as well as communication. The space environment is harsh with criss-crossing charged particles, a good fraction of which originates from the Sun. The protection of our space asset depends crucially on our ability to understand the space weather and possibly predict the changes well in advance. The instruments on-board the Aditya-L1 mission will enhance our understanding of these phenomena and make such forecasts possible.
Space missions that travel beyond the Earth’s sphere of influence are marked by two major challenges. One is space navigation and the other is communication with ground facilities. This is the first time Isro is launching a mission this far into space. Navigation in this direction is also being performed for the first time. With our capability to navigate to the Moon and Mars, this is not an insurmountable task. Not only reaching the Sun-Earth L1 point but also making a halo orbit, as the Earth moves around the Sun, are crucial tasks for the mission team. There will be a variety of operations that need to be performed as part of this mission, which is definitely technologically daunting. Due to the limited visibility of the spacecraft with Indian ground stations, Isro plans to collaborate with other agencies for communication and data download. The instruments that need to collect data 24/7 are certain to accumulate a large volume of it. The demand is not only to quickly download the data, but also to analyse it almost immediately to monitor the Sun’s activity in near real-time. These requirements place a lot of demand on the communication links between the spacecraft and ground stations.
The seven instruments on board this mission are of two types: Remote-sensing instruments that view the Sun and make measurements, and in situ instruments that make estimations at the location of the spacecraft. These instruments are highly sophisticated and perform very complex and precise measurements. High cadence and precise estimations of the dynamic Sun and its corona are expected to be a game changer in our understanding of the Sun.
Studies of the Sun in India have a very long history spanning more than 200 years. The Madras observatory, which was established in 1792, carried out studies of the Sun and other celestial objects. The experiments carried out during the 1868 total solar eclipse in Guntur contributed to the discovery of the element helium. The Kodaikanal observatory, currently a field station of the Indian Institute of Astrophysics (IIA), was set up in 1899 to carry out studies of the Sun using various ground-based instruments. More than 100 years of images of the Sun preserved by IIA are now digitised and made available to the scientific community to research on the long-term variations of the Sun. The Indian solar physics community has played a very significant role in shaping the international landscape in solar research. In this context, the data collected by the state-of-the-art instruments on board the Aditya-L1 mission will be a shot in the arm for Indian researchers. It will set new limits for our space ambitions
Annapurni Subramaniam is director, Indian Institute of Astrophysics. The views expressed are personal