Aditya-L1

Aditya-L1 (Sanskrit: Āditya IPA: [aːd̪it̪jɐ] 'Sun', L1 'Lagrange Point 1') is a coronagraphy spacecraft for studying the solar atmosphere, designed and developed by ISRO and various other Indian Space Research Institutes. It is orbiting at about 1.5 million km from Earth in a halo orbit around the Lagrange point 1 (L1) between the Earth and the Sun, where it will study the solar atmosphere, solar magnetic storms, and their impact on the environment around the Earth.

It is the first Indian mission dedicated to observe the Sun. Nigar Shaji is the project's director. Aditya-L1 was launched aboard the PSLV C57 at 11:50 IST on 2 September 2023. It successfully achieved its intended orbit nearly an hour later, and separated from its fourth stage at 12:57 IST. It was inserted at the L1 point on 6 January 2024, at 4:17 pm IST.

The main objectives of Aditya-L1 are:

The mission was conceptualised in January 2008 by the Advisory Committee for Space Sciences (ADCOS). It was initially envisaged as a small, 400 kg (880 lb) satellite in a Low Earth Orbit (800 km) with a coronagraph to study the solar corona. An experimental budget of ₹3 crore was allocated for the financial year 2016–2017. The scope of the mission has since been expanded and it became a comprehensive solar and space environment observatory to be placed at Lagrange point 1 (L1), hence the mission was renamed as Aditya-L1. As of July 2019^[update], the mission has an allocated cost of ₹378 crores, excluding launch costs.

The European Space Operations Centre (ESOC), operated by the European Space Agency (ESA) is supporting the mission.

On 11 January 2024, ISRO successfully deployed a 6-meter magnetometer boom aboard the Aditya-L1 in the Halo orbit at the Lagrange Point L1. After the liftoff, the boom had been stowed for 132 days. The in-orbit deployment period that was measured was roughly 9 seconds, which is well within the 8–12 second prediction range. The magnetometer boom will measure the low-intensity interplanetary magnetic field in space using two high-accuracy fluxgate magnetometer sensors that are carried aboard. In order to reduce the impact of the spacecraft's magnetic field on measurements, the sensors are placed 3 and 6 meters away from the craft. Using a dual sensor system also helps to cancel out the spacecraft's magnetic influence and facilitates accurate estimation. The carbon-fiber-reinforced polymers (CFRP) was used in the construction of the boom segments. Through the use of spring-driven hinge mechanisms, the five pieces are joined to enable folding in close proximity to the craft throughout the journey and opening up upon reaching the desired orbit. The hinges lock into place as the mechanism fans out. In the stowed position, two hold-downs firmly secure the boom in place. Information obtained via the telemetry switches validates the release of the hold-down, the initial motion, and the locking of every hinge.

The mission took 126 Earth days after launch to reach the halo orbit around the L1 point, which is about 1,500,000 km (930,000 mi) from Earth. The spacecraft is planned to remain in the halo orbit for its mission duration while being maintained at a stationkeeping Δv of 0.2–4 m/s per year. The 1,500 kg (3,300 lb) satellite carries seven science payloads with various objectives, including instruments to measure coronal heating, solar wind acceleration, coronal magnetometry, origin and monitoring of near-UV solar radiation (which drives Earth's upper atmospheric dynamics and global climate), coupling of the solar photosphere to the chromosphere and corona, and in-situ characterisations of the space environment around Earth by measuring energetic particle fluxes and magnetic fields of the solar wind, and solar magnetic storms.

Aditya-L1 will provide observations of the Sun's photosphere, chromosphere and corona. Its scientific payloads must be placed outside the interference from the Earth's magnetic field, and hence, could not have been useful in the low Earth orbit, as proposed in the original mission concept back in 2008.