Aditya-L1 (Sanskrit: '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 observing 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.
Mission objectives
The main objectives of Aditya-L1 are:
To observe the dynamics of the solar chromosphere and corona: To study chromospheric and coronal heating, the physics of partially ionised plasma, of coronal mass ejections (CMEs) and their origins, of the coronal magnetic field and heat transfer mechanisms, and of flare exchanges. To observe the physical particle environment around its position. To determine the sequence of processes in multiple layers below the corona that lead to solar eruptions. To study space weather, and the origin, composition and dynamics of solar wind. To observe the in-situ particle and plasma environment providing data for the study of particle dynamics from the Sun. To study the factors affecting coronal and coronal loop plasma, such as temperature, velocity, and density. To analyse magnetic field topology and magnetic field measurements in the solar corona.
Mission history
Development
The mission was conceptualised in January 2008 by the Advisory Committee for Space Sciences (ADCOS). It was initially envisaged as a small, satellite in a Low Earth Orbit (800 km) with a coronagraph to study the solar corona. An experimental budget of 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. , the mission has an allocated cost of , excluding launch costs. 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.
One of the major unsolved problems in the field of solar physics is coronal heating. The upper atmosphere of the Sun has a temperature of , whereas the lower atmosphere is just . In addition, it is not understood exactly how the Sun's radiation affects the dynamics of the Earth's atmosphere on a shorter as well as a longer time scale. The mission will obtain near-simultaneous images of the different layers of the Sun's atmosphere, which will reveal the ways in which energy is channeled and transferred from one layer to another. Thus, the mission will enable a comprehensive understanding of the dynamical processes of the Sun and address some of the outstanding problems in solar physics and heliophysics. Launch
Aditya L1 was mounted on a PSLV-XL carrier rocket with flight designation C57. The 44 meters tall rocket considered of four alternating solid fueled and liquid-fueled stages, along with 6 small solid rocket boosters. The combined rocket weighed in at about 321 tonnes. On 2 September 2023, at 11:50 IST, the Polar Satellite Launch Vehicle (PSLV-C57) accomplished a successful launch of the Aditya-L1It was inserted into a highly elliptical orbit around the earth with a perigee of 235 km and an apogee of 19500 km, inclined 19.2° to the earth. The spacecraft was launched from the Second Launch Pad of the Satish Dhawan Space Centre (SDSC) located in Sriharikota at a launch Azimuth off 104°.Editable Text Artwork for Web Upload copy Aditya-L1, following a flight duration of 63 minutes and 20 seconds, achieved a successful injection into an elliptical orbit around the Earth at 12:54 IST.
The launch was applauded by Dr Jitendra Singh Rana , India's Union minister for Science and Technology.
Orbit-raising burns
First orbit-raising burn On 3 September 2023, the Aditya-L1 performed its first Earth-bound maneuver, raising its orbit to a into orbit.
Second orbit-raising burn On 5 September 2023, Aditya-L1 performed its second Earth-bound maneuver, raising its orbit to a into orbit.
Third orbit-raising burn On 10 September 2023, Aditya-L1 performed its third Earth-bound maneuver, raising its orbit to a into orbit.
Fourth orbit-raising burn On 15 September 2023, Aditya-L1 performed its fourth Earth-bound maneuver, raising its original orbit to a into orbit. This was the last of such maneuvers, being directly followed by the Trans-Lagrangian 1 Injection, which took place on 19 September.
Trans-Lagrangian 1 Injection On 19 September 2023, Aditya-L1 performed its last maneuver around Earth to escape its orbit and headed towards the Lagrange 1 point, taking at least four months to further reach its destination, 1.5 million kilometers away.
On 30 September 2023, Aditya-L1 had escaped the Earth's sphere of influence and was on the way to the Lagrange point 1. During this journey a week before Orbital Insertion, the SUIT instrument captured an X-class solare flare and a CME on 31 December 2023. This was the first observations of a solar flare using near-UV light.
Trajectory correction maneuver On 6 October 2023, Aditya-L1 performed a Trajectory Correction maneuvre (TCM1). It was needed to correct the trajectory evaluated after tracking the Trans-Lagrangian Point 1 Insertion (TL1I) maneuver performed on 19 September 2023.
Orbital Insertion Aditya-L1 underwent a series of four Earth-bound orbital maneuvres prior to its injection into a transfer orbit towards the Lagrange point (L1). It reached its designated orbit at the L1 point, which is about from Earth 126 days after its launch on 6 January 2024 at 4:17 IST. A small controlled firing of the spacecraft's liquid rocket engine was conducted to gently nudge it into an orbit around the L1 point.
Aditya-L1 completed its first halo orbit around the L1 point on 2 July 2024. It takes it approximately 178 days to complete each orbit. It underwent two station-keeping maneuvers on 22 February and 7 June, and later one on 2 July. The European Space Operations Centre (ESOC), operated by the European Space Agency (ESA), supported the mission all through this phase. Its orbit is around 1% of the distance between the earth and the sun. The spacecraft is planned to remain in its present halo orbit for the entire mission duration while being maintained at a stationkeeping Δv of 0.2–4 m/s per year.
Payloads
The instruments of Aditya-L1 are tuned to observe the solar atmosphere, mainly the chromosphere and corona. In-situ instruments will observe the local environment at the L1 point. There are seven payloads on board, with four for remote sensing of the Sun and three for in-situ observation. The payloads have been developed by different laboratories in India with the close collaborations of various ISRO centers. The satellite carries seven scientific payloads, including instruments to measure and monitor coronal heating, solar wind acceleration, coronal magnetometry, the origin of near-UV solar radiation (which drives Earth's upper atmospheric dynamics and global climate), the 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.
TypeSl.NoPayloadCapabilityLaboratoriesRemote Sensing Payloads1Visible Emission Line Coronagraph (VELC)Corona Imaging and spectroscopyIndian Institute of Astrophysics, Bangalore2Solar Ultraviolet Imaging Telescope (SUIT)Photosphere and chromosphere imaging-narrow and broadbandInter University Centre for Astronomy & Astrophysics, Pune3Solar Low Energy X-ray Spectrometer (SoLEXS)Soft X-ray spectrometer: Sun-as-a-star observationU R Rao Satellite Centre, Bangalore4High Energy L1 Orbiting X-ray Spectrometer (HEL1OS)Hard X-ray spectrometer: Sun-as-a-star observationIn-situ Payloads5Aditya Solar wind Particle Experiment (ASPEX)Solar wind and Particle analyzer: Protons and Heavier ions with directionsPhysical Research Laboratory, Ahmedabad6Plasma Analyser Package For Aditya (PAPA)Solar wind and Particle Analyzer: Electrons and Heavier Ions with directionsSpace Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram7Advanced Tri-axial High Resolution Digital MagnetometersIn-situ magnetic field (Bx, By and Bz).Laboratory for Electro Optics Systems, Bangalore
Visible Emission Line Coronagraph (VELC) The Visible Emission Line Coronagraph (VELC) is a primary payload aboard on the Aditya spacecraft. The VELC is an internally occulted reflective coronagraph designed to fulfil specific observation needs. The instrument allows for high spatial resolution imaging 1.25-2.5 arcseconds of the Sun's corona, simultaneous observations in three modes (Imaging, Spectroscopy and Spectro-polarimetry), and even utilizes artificial intelligence to aid in the detection of coronal mass ejections (CMEs). The instrument was developed by Indian Institute of Astrophysics, Bengaluru.
Solar Ultraviolet Imaging Telescope (SUIT) The SUIT is an ultraviolet imaging telescope designed to study the solar spectral radiation in the ultraviolet range.It operates within the wavelength range of 200–400 nm, using both narrowband and broadband filters. The SUIT utilises 11 different filters. The filters have been selected carefully to ensure coverage of the lower (photosphere) and middle (chromosphere) atmosphere of the Sun, the first approach of its kind in such observations. The SUIT provides near-simultaneous coverage of the solar atmosphere, from lower photosphere to the upper chromosphere. The instrument was developed by Inter University Centre for Astronomy & Astrophysics, Pune, in collaboration with ISRO.
Solar Low Energy X-ray Spectrometer (SoLEXS) The SoLEXS is an X-ray spectrometer designed to continuously measure the solar soft X-ray flux (2 keV-22 keV) from the Sun-Earth Lagrangian point L1. These measurements can be used to better understand the properties of the Sun's corona, in particular, why the temperature of the corona is so high. The SoLEXS will observe solar flares, and in conjunction with data provided by the VELC, will help study the complex thermal properties of the Sun's outer layers. The instrument was developed by U. R. Rao Satellite Centre, Bengaluru.
High Energy L-1 Orbiting X-ray Spectrometer (HEL1OS) Developed by the Space Astronomy Group, URSC, the HEL1OS (pronounced helios) is an x-ray spectrometer designed to study solar flares in the x-ray spectrum, in particular, energy bands of 10-150 Kev (kilo-electron volts). Using a twin-pair of Cadmium Telluride (CdTe) and Cadmium Zinc Telluride (CZT) detectors, the instrument aims to study the acceleration and movement of electrons in the Sun's corona, as well as to study the cut-off energy between thermal and non-thermal solar emissions.
Aditya Solar Wind Particle Experiment (ASPEX)