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Aditya-L1: India's first spacecraft to study the Sun

Following its groundbreaking achievement as the first nation to land a spacecraft near the lunar south circumpolar region, India is now shifting its focus to exploring the sun, as Aditya L1 takes off on September 2, The mission will transmit data from the First Lagrangian point, which is about 1.5 million km from Earth

The launch of Aditya-L1, India's first observatory satellite to study the Sun, is scheduled for September 02, 2023, at 11:50 IST (06:20 GMT) from the SLP Second Launch Pad at Sriharikota Spaceport. The Indian Space Research Organization (ISRO) PSLV-XL C57 launcher will place the satellite in a halo orbit around the Lagrangian 1 (L1) point of the Sun-Earth system, which is 1.5 million km from Earth, with the great advantage of continuously viewing the Sun without any occultations or eclipses. The spacecraft will be launched into

235 km x 19500 km orbit at an inclination of 19.2° by a PSLV-XL in full power configuration with six solid-fuel auxiliary boosters.

First Indian mission to study the Sun

The Aditya-1 spacecraft was conceived as a 400 kg class satellite (chassis I-2000) carrying a payload, the Visible Emission Line Coronagraph (VELC), and was planned to be launched into a low earth orbit of 800 km. Then, reasoning that a satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system has the great advantage of continuously viewing the Sun without any occultations/eclipses, the scientists decided that Aditya-1 should be revised to "Aditya-L1" and would be inserted into the halo orbit of L1, which is 1.5 million km from Earth. In the new design, the spacecraft carries seven payloads to observe the Sun's photosphere, chromosphere, and outermost layers (the corona) using electromagnetic, particle, and magnetic field detectors. Using the L1 special viewpoint.

After reaching low orbit, the satellite will be maneuvered using its onboard engines. “A series of burning elliptical orbital maneuvers will be conducted to raise its orbit towards the L1 Lagrange point to overcome the Earth's gravitational pull. The estimated time required to reach the L1 point is about 109 days,” said Dr Suresh Kumar, former senior scientist at ISRO. Once the Aditya L1 mission reaches the L1 Lagrange point, it will be injected into a halo orbit. A halo orbit is a type of orbit that allows the satellite to remain in a stable position between the Earth and the Sun. The satellite will use its onboard scientific instruments to study the dynamics of the Sun's chromosphere and corona, its magnetic field and its solar flares, solar wind, etc. The data collected by the Aditya L1 mission will help scientists better understand the Sun and its nature. impact on Earth.

"The Sun, as our nearest star, holds a central role in sustaining life on Earth and is the source of all energy. Understanding whether the Sun will continue emitting radiation at its current levels or undergo transformative changes bears immense importance. Any fluctuations in solar radiation could exert a substantial impact on our planet's climate," emphasizes Prof Dipankar Banerjee, who is part of a team that conceptualized the mission more than 10 years ago..

The extended duration of monitoring the Sun from the Lagrangian point is poised to unveil a heretofore concealed history of the Sun's behavior. Scientific observations have already revealed a cyclic pattern of magnetic activity on the Sun, commonly referred to as the solar cycle, as well as sporadic, forceful alterations in its magnetic field, resulting in solar storms. These magnetic fields in the Sun's outer atmosphere, known as the corona, can sporadically release gas and magnetic field bubbles, referred to as coronal mass ejections, which have the potential to disrupt satellites and celestial bodies, including the Moon. This underscores the critical role of space weather forecasting.

Aditya-L1 is poised to supply essential data for enhancing space weather predictions, safeguarding space assets, and potentially shedding light on Earth's climatic history, as solar activities can exert a profound influence on the composition of Earth's atmosphere and, conceivably, on phenomena such as ice ages.

One of the mission's groundbreaking objectives is to provide an estimate of the magnetic field in the solar corona, a pioneering endeavor that has never been accomplished from a space platform. Additionally, the spacecraft will continuously monitor the near-ultraviolet radiation emitted by the Sun and study various properties of the solar wind, advancing our understanding in these domains.

Ground-based telescopes will complement Aditya-L1's observations, offering a holistic perspective on solar activities, particularly solar storms. Collaborative efforts between observatories located in ARIES, Kodaikanal, and Udaipur will play a pivotal role in gathering data crucial for comprehending these intricate phenomena.

As Aditya-L1's scientific payloads commence their operations, an extensive data analysis effort will be undertaken. The spacecraft's strategic position at the Lagrangian point, where gravitational forces balance, facilitates prolonged observations and enhances our capacity to scrutinize the Sun comprehensively.

Aditya-L1's instruments will be tuned to observe the solar atmosphere mainly the chromosphere and corona. In-situ instruments will observe the local environment in L1. Of the seven payloads, four of them perform remote sensing of the Sun and three perform in situ observation.

Science Objectives:

The major science objectives of Aditya-L1 mission are:

  • Study of Solar upper atmospheric (chromosphere and corona) dynamics.

  • Study of chromospheric and coronal heating, physics of the partially ionized plasma, initiation of the coronal mass ejections, and flares

  • Observe the in-situ particle and plasma environment providing data for the study of particle dynamics from the Sun.

  • Physics of solar corona and its heating mechanism.

  • Diagnostics of the coronal and coronal loops plasma: Temperature, velocity and density.

  • Development, dynamics and origin of CMEs.

  • Identify the sequence of processes that occur at multiple layers (chromosphere, base and extended corona) which eventually leads to solar eruptive events.

  • Magnetic field topology and magnetic field measurements in the solar corona.

  • Drivers for space weather (origin, composition and dynamics of solar wind.

The Aditya-1 spacecraft was designed on an I-2000 chassis

Scientific instruments

The Solar Ultraviolet Imaging Telescope (SUIT) payload photographs the solar photosphere and chromosphere in the near ultraviolet (UV) and also measures changes in solar irradiance in the near UV. SUIT was developed by the Inter-University Center for Astronomy and Astrophysics of Pune (IUCAA) and was handed over to ISRO. The SUIT payload is expected to provide crucial information for understanding the problem of coronal heating, coronal mass ejection, pre-burning and explosion activities and their characteristics, space weather dynamics, propagation and particle fields, etc. “We had to build an ultra-clean room, in addition to ensuring that there would be no contamination from particles scattered by the Sun in the payload. Special filters had to be designed to catch the radiation,” said Dr. Kumar. “SUIT, for the first time, will allow us to record images at this wavelength crucial for maintaining the ozone and oxygen content in the Earth's atmosphere. SUIT will also measure UV radiation dangerous to human health.” The SUIT project has involved more than 200 scientists over the last ten years. In addition to ISRO's initial grant of Rs 25 million for the equipment, scientists faced several challenges during the development of the payload, including building an ultra-clean room and designing special filters to capture radiation.

The Visible Emission Line Coronagraph (VELC) studies the solar corona and the dynamics of coronal mass ejections.

The Aditya Solar wind Particle EXperiment (ASPEX) and Plasma Analyzer Package for Aditya (PAPA) payloads study the solar wind and energetic ions, as well as their energy distribution.

The ASPEX payload comprises 2 subsystems: SWIS and STEPS

SWIS (Solar Wind Ion Spectrometer) is a low-energy spectrometer that

is designed to measure the proton and alpha particles of the solar wind.

STEPS (Suprathermal and Energetic Particle Spectrometer)is a high-energy

spectrometer that is designed to measure high-energy ions of the solar wind.

The solar low-energy X-ray spectrometer (SoLEXS) and the high-energy L1 orbital X-ray spectrometer (HEL1OS) study the Sun's X-ray bursts over a wide range of X-ray energy.

The magnetometer will be able to measure interplanetary magnetic fields at point L1.

Aditya L1's scientific payloads were Indigenously developed by different laboratories in the country. The VELC instrument was developed at the Indian Institute of Astrophysics, Bangalore; the SUIT instrument at Inter University Center for Astronomy & Astrophysics, Pune; ASPEX Instrument at Physical Research Laboratory, Ahmedabad; the PAPA payload at Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram; SoLEXS and HEL1OS payloads at the UR Rao Satellite Center, Bangalore, and the magnetometer payload at the Electro-Optical Systems Laboratory, Bangalore.

All payloads are developed in close collaboration with various centers of ISRO.

Launch and Deployment PSLV-C57 / Aditya-L1

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