Aditya L1 Mission

In December 2015, the Government has made clear that: India will launch Chandrayan-II in 2017 and its first Solar Mission Aditya L1 in around 2019. This article is a backgrounder on Aditya L1 mission.

What is Aditya L1?

Aditya-L1 is the India’s first dedicated scientific mission to study the sun. The mission is a joint venture between ISRO and physicists from various institutes including Indian Institute of Astrophysics, Bengaluru; Inter University Centre for Astronomy and Astrophysics, Pune; and Tata Institute of Fundamental Research, Mumbai. The mission costs approximately Rs. 378 crores.

The project was conceived in 2008. Initially it was planned to launch the Aditya-1 satellite as a low-earth orbit satellite but subsequently the plan was changed and now ISRO is planning to place the satellite at Lagrangian point L1. The upgraded mission is called Aditya-L1.

Where the satellite will be placed?

Initially ISRO planned to place the 200 kg satellite at an altitude of 800 km to coincide with the solar maximum. Solar maximum is a period of intense activity on the sun and it occurs once in every 11 years.

As per the revised plan, ISRO will put the satellite in a halo orbit around the L1 Lagranian point between the Sun and the Earth. The distance of this point from earth is about 1.5 million km. The location will facilitate continuous viewing of the Sun without any eclipses.  The satellite will be launched by using the PSLV XL.

What are Lagrangian points and halo orbit?

Lagrangian points are the locations in space where the combined gravitational pull of two large masses roughly balance each other. Any small mass placed at that location will remains at constant distances relative to the large masses. There are five such points in Sun-Earth system and they are denoted as L1, L2, L3, L4 and L5. A halo orbit is a periodic three-dimensional orbit near the L1, L2 or L3.

What are the objectives of the mission?

• The objective of the mission is to study the dynamic nature of the sun’s outer most layers, the corona and the chromosphere, and collect data about Coronal Mass Ejections (CME).
• It will also study on origin of solar storms and their path through the interplanetary space from the Sun to the Earth.
• The studies will also focus on collection of information for space weather prediction.

What is the significance of the mission?

Solar storms occur when the Sun releases huge bursts of energy in the form of solar flares and coronal mass ejections. Solar flares are the sudden explosions on the Sun. Solar flares are often, not always, followed with release of huge streams of plasma. These streams are called coronal mass ejections. These activities on the Sun send a stream of electrical charges and magnetic field toward the Earth causing severe near-Earth-space disturbances called geomagnetic storms. They disturb the communication networks, power lines in high altitudes and satellite-based operations. They impact satellite mission lifetimes. They also affect the positional accuracy of satellites and thus impact GPS navigational networks. Basic understanding of various processes on the Sun’s out layers and continuous monitoring will help us to better protect the satellites by taking necessary action. Data from Aditya-L1 mission will also complement our scientists in building of space weather forecasting models. Presently Indian scientists use the models and calculations made by NASA to maintain the satellites.

What are the payloads developed for the mission?

Aditya-L1 mission will carry seven payloads. They are:

• Visible Emission Line Coronagraph (VELC) – It will study the diagnostic parameters of solar corona and dynamics and origin of Coronal Mass Ejections (CMEs). It can measure the magnetic field of solar corona down to tens of Gauss.
• Solar Low Energy X-ray Spectrometer (SoLEXS) – The payload is aimed at monitoring the X-ray flares (1 – 30 keV) for studying the heating mechanism of the solar corona.
• High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) – It is designed to study hard X-ray emission from 10 keV to 150 keV during the impulsive phase of solar flares.
• Solar Ultraviolet Image Telescope (SUIT) – It will image the spatially resolved Solar Photosphere and Chromosphere in near UV region and measure solar irradiance variations.
• Plasma Analyser Package for Aditya (PAPA) – It aims to study composition of solar wind and its energy distribution throughout the lifetime of mission.
• Aditya Solar Wind Particle Experiment (ASPEX) – It will study the variation of solar wind properties, its distribution and spectral characteristics.
• Magnetometer – It is used to measure the magnitude and nature of the interplanetary magnetic field.

The challenge before ISRO is in placing the satellite at L1 point where it will send Indian spacecraft for the first time.