Context: India’s maiden solar mission, Aditya-L1, has achieved a crucial milestone by reaching the Lagrangian point (L1) after 127 days since its launch on September 2, 2023. 

• The spacecraft has been carefully placed in a periodic halo orbit, approximately 1.5 million km from Earth, by ISRO scientists and engineers.

Precision Orbit Insertion

• Aditya-L1 was placed in the halo orbit through a firing manoeuvre conducted by ISRO scientists at ISTRAC, Bengaluru.

• Precise calculations and corrections were made to ensure the spacecraft’s exact placement in the intended halo orbit around the Lagrangian point.

Characteristics of the Orbit

• The halo orbit is periodic, involving the continuous movement of the sun, earth, and the spacecraft.

• The selected orbit, located 1.5 million km from Earth, has an orbital period of about 177.86 Earth days.

• The specific halo orbit minimizes station-keeping manoeuvres, reducing fuel consumption and ensuring a continuous, unobstructed view of the sun.

What is Aditya-L1 Mission?

• Aditya-L1 is India’s inaugural solar mission, designed as a space-based observatory for Sun study, with a life expectancy of five years.

• The spacecraft will be positioned in a halo orbit around the Sun-Earth L1 point, located about 1.5 million km away.

• The strategic halo orbit ensures continuous solar observation without any interruptions such as occultation or eclipse.

• Aditya-L1 is equipped with seven payloads, including electromagnetic and particle detectors. These payloads will facilitate observations of various solar layers, namely the photosphere, chromosphere, and corona.

• Three of the payloads will conduct in-situ studies of particles and fields at the L1 point.

• The mission aims to enhance our understanding of solar activities by utilizing the advantageous position of L1.

Major Science Objectives of the Aditya-L1 Mission

• Understanding the coronal heating and solar wind acceleration. 

• Understanding initiation of Coronal Mass Ejection (CME), flares and near-earth space weather. 

• To understand the coupling and dynamics of the solar atmosphere. 

• To understand solar wind distribution and temperature anisotropy. 

Significance

Mission Lifetime and Efficiency

• The chosen halo orbit ensures a mission lifetime of 5 years, allowing for prolonged observation of the sun.

• Minimizing station-keeping manoeuvres increases mission efficiency by conserving fuel resources.

Advanced Scientific Observation

• Aditya-L1 carries seven payloads designed to observe the photosphere, chromosphere, and the sun’s outermost layer (corona).

• The use of electromagnetic and particle detectors enhances scientific understanding of solar phenomena.

Lagrange points

• According to the ISRO, for a two-body gravitational system, the Lagrange Points are the positions in space where a small object tends to stay if put there. 

• These points in space for a two-body system such as the sun and Earth can be used by the spacecraft to remain at these positions with reduced fuel consumption. For two-body gravitational systems, there are a total of five Lagrange points, denoted as L1, L2, L3, L4, and L5.

What is the L1 point?

• The L1 lies between the sun-earth line which is about 1.5 million km from the earth. The distance of L1 from Earth is approximately 1% of the Earth-sun distance. 

• A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the sun without any occultation/eclipse. 

• This will provide a greater advantage of observing solar activities continuously.

• There are currently four operational spacecraft at L1 which are WIND, Solar and Heliospheric Observatory (SOHO), Advanced Composition Explorer (ACE) and Deep Space Climate Observatory (DSCOVER).