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” Halo Orbit: Solar Observations “
The Aditya-L1 spacecraft moves in a periodic halo orbit about 1.5 million km away from Earth, following a path that always lies along a line between the Sun and Earth. It takes around 178 days to complete one orbit.
A halo orbit is a special kind of orbit that goes around a point in space where the gravity of two large objects, like the Sun and the Earth, balance each other. This point is called a Lagrange point. A spacecraft in a halo orbit can stay in the same position relative to the Sun and the Earth, which is useful for some scientific missions. A halo orbit looks like a ring or a halo around the Lagrange
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The Aditya-L1 mission is a solar observatory from India that will be stationed at a specific point called Lagrangian point L1. The mission’s goal is to continuously observe and study the movements and behaviors of the Sun’s chromosphere and corona. By placing Aditya-L1 in a halo orbit around L1, there are advantages compared to placing it in a Low Earth Orbit (LEO).
1 .It provides a smooth Sun-spacecraft velocity change throughout the orbit, appropriate for helioseismology
● Helioseismology is the study of the interior of the sun by observing waves on its surface. These waves are caused by sound vibrations inside the sun, and analyzing them helps scientists understand more about the sun’s internal structure and processes.
2. The satellite is located beyond Earth’s magnetosphere, making it perfect for gathering and studying solar wind and particles right from the source.
3 . It provides a clear, constant view of the Sun, and can also see Earth continuously, ensuring uninterrupted communication with ground stations.
“Aditya-L1: Navigating Solar Challenges “
“Inserting the spacecraft into the L1 halo orbit is challenging,”
Only NASA, the American space agency, and the European Space Agency (ESA) have previously sent spacecraft to the L1 point. NASA’s “Wind” spacecraft was deployed in 1994, followed by the joint NASA-ESA “Solar and Heliospheric Observatory (SOHO) “in 1995, and NASA’s “Advanced Composition Explorer” (ACE) in 1997.
Aditya-L1 is expected to carry out its observational mission for a minimum of five years.
The placement of Aditya-L1 in its halo orbit required accurate steering and management, according to Isro’s announcement. This achievement showcases Isro’s skills in handling difficult space moves and boosts their confidence for upcoming space missions.
“A solar physicist from the Indian Institute of Science Education and Research in Kolkata explained to a media outlet that to place the fast-moving spacecraft into the halo orbit, they had to slow it down and change its path by using its onboard engines.”
“It’s similar to getting off a fast highway and taking a smaller road to reach the area around L1. Doing this efficiently means using less fuel, which leads to a longer mission life ,” explained the solar physicist, who led a team discussing how Aditya-L1 could help in space weather research.
The instruments on Aditya-L1, designed for observing the Sun, will investigate solar storms and flares, and explore a long-standing puzzle: why the solar corona which is the outermost layer and which is the Sun’s atmosphere, has a temperature of a million degrees Celsius, significantly hotter than the solar surface’s (photosphere ) temperature of 6,000°C which is much nearer to the Sun’s Core where heat is generated through nuclear fusion.
The seven scientific instruments on Aditya-L1 examining solar activity near the L1 point could help create warnings for space weather — events like large particle bursts caused by solar magnetic storms that could interfere with satellite functioning.
A solar physicist explained that based on the strength and direction of solar emissions, an alert from Aditya-L1 could offer a warning about 30 minutes before these events affect the Earth. These solar occurrences can harm satellites orbiting the Earth. Having a few minutes’ warning could give space agencies enough time to respond, like turning off essential systems to avoid damage.
Girish Linganna Aerospace and Defense Analyst (The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany. You can reach out to him at: girishlinganna@gmail.com)