Solar mission spacecraft Aditya-L1 gets send off from Earth as ISRO performs key manoeuvre

Aditya-L1, India’s first space-based mission to study the sun, on Tuesday, left earth-bound orbits to enter its trajectory towards Lagrange point 1 (L1) from where it will observe the sun.

The Indian Space Research Organisation (Isro) successfully performed the Trans-Lagrangian Point 1 Insertion (TL1I) at around 2 am, marking the commencement of the spacecraft’s 110-day journey to L1.

“Off to Sun-Earth L1 point! The Trans-Lagrangian Point 1 Insertion (TL1I) manoeuvre is performed successfully. The spacecraft is now on a trajectory that will take it to the Sun-Earth L1 point. It will be injected into an orbit around L1 through a manoeuvre after about 110 days. This is the fifth consecutive time ISRO has successfully transferred an object on a trajectory toward another celestial body or location in space,” Isro said.

The TL1I marks the send-off for the spacecraft from the earth-bound orbits towards the L1 point, about 1.5 million km from the earth. Aditya-L1 took off with seven payloads from the Satish Dhawan Space Centre in Sriharikota (SDSC-SHAR) on September 2.

Sensors at work

The collection of scientific data as part of the mission has commenced. The sensors of the STEPS (Supra Thermal and Energetic Particle Spectrometer) instrument have measured supra-thermal and energetic ions and electrons at distances greater than 50,000 km from the earth. The instrument is part of the Aditya Solar wind Particle EXperiment (ASPEX) payload.

The data collected during the spacecraft’s 16-day stay on the earth’s orbits will help scientists analyse the behaviour of particles surrounding the earth, especially in the presence of the earth’s magnetic field.

Each of the six sensors in the instrument carries out observations in different directions and measures the supra-thermal and energetic ions ranging from 20 keV/nucleon to 5 MeV/nucleon, in addition to electrons exceeding 1 MeV.

Supra-thermal ions are accelerated ions with significantly high energies. One keV (kilo electron volt) is 1,000 electron volts (units used to measure the amount of kinetic energy an electron gains as it accelerates in an electric field created by the increase of one Volt). One MeV is one million electron volts.

Isro said STEPS was activated on September 10 at a distance greater than 50,000 km from the earth (equivalent to more than eight times the earth's radius), well beyond the earth's radiation belt region. “After completing the necessary instrument health checks, data collection continued until the spacecraft had moved farther than 50,000 km from earth,” it said.

The STEPS measurements will continue during Aditya-L1’s cruise phase leading up to L1 and once it is positioned on its intended orbit. Data collected around L1 will provide insights into the origin, acceleration, and anisotropy (quality of exhibiting different properties when measured along different directions) of solar wind and space weather phenomena.

STEPS was developed by the Physical Research Laboratory with support from the Space Application Centre in Ahmedabad.