Successful launch of India’s first Solar Mission, Aditya -L1

Congratulations to our scientists and engineers and all the team members of ISRO for the successful launch of India’s first Solar Mission, Aditya -L1.

- Sanjay Verma

· After successful landing of Chandrayan-3 on moon, India successfully launched Aditya L1 Mission from Satish Dhawan Space Centre, Sriharikota

About Aditya L1 Mission:

Aditya L1 is the first space-based Indian mission to study the Sun planned by the Indian Space Research Organisation (ISRO)
Aditya L1 launched has been launched using the Polar Satellite Launch Vehicle (PSLV) with 7 payloads (instruments) on board.

The 7 payloads include:

VELC
Solar Ultraviolet Imaging Telescope (SUIT)
Solar Low Energy X-ray Spectrometer (SoLEXS)
Aditya Solar wind Particle Experiment (ASPEX)
High Energy L1 Orbiting X-ray Spectrometer (HEL1OS)
Plasma Analyser Package for Aditya (PAPA)

The spacecraft shall be placed in a halo orbit around the Lagrange point 1 (L1) of the Sun-Earth system, which is about 1.5 million km from the Earth.
A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the Sun without any occultation/eclipses.
This will provide a greater advantage in observing solar activities and their effect on space weather in real-time.
The spacecraft carries seven payloads to observe the photosphere, chromosphere and the outermost layers of the Sun (the corona) using electromagnetic and particle and magnetic field detectors.
Using the special vantage point L1, four payloads directly view the Sun and the remaining three payloads carry out in-situ studies of particles and fields at the Lagrange point L1, thus providing important scientific studies of the propagatory effect of solar dynamics in the interplanetary medium.
The other objectives of Aditya L1 mission will be to understand the drivers for space weather (origin, composition and dynamics of solar wind), and identify the sequence of processes that occur at multiple layers (chromosphere, base and extended corona) which eventually leads to solar eruptive events.

About L1 :

L1 refers to Lagrangian/Lagrange Point 1, one of 5 points in the orbital plane of the Earth-Sun system.
Lagrange Points are positions in space where the gravitational forces of a two-body system like the Sun and Earth produce enhanced regions of attraction and repulsion.
These can be used by spacecraft to reduce fuel consumption needed to remain in position.
A Satellite placed in the halo orbit around the L1 has the major advantage of continuously viewing the Sun without any occultation/ eclipses.
The L1 point is home to the Solar and Heliospheric Observatory Satellite (SOHO), an international collaboration project of National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA).

About Polar Satellite Launch Vehicle (PSLV)

It is the third generation launch vehicle of India.
It is the first Indian launch vehicle to be equipped with liquid stages.
The first successful launch of PSLV was in October 1994.
There is a total of 4 stages in this launch vehicle.

First Stage – PS 1 – PSLV uses the S139 solid rocket motor that is augmented by 6 solid strap-on boosters.
Second Stage – PS 2 – PSLV uses an Earth storable liquid rocket engine for its second stage, known as the Vikas engine, developed by Liquid Propulsion Systems Centre.
Third Stage – It is a solid rocket motor that provides the upper stages high thrust after the atmospheric phase of the launch.
Fourth Stage – The PS4 is the uppermost stage of PSLV, comprising of two Earth storable liquid engines.

It has the following variants:

PSLV-G: It has strap-on motors
PSLV – CA: It does not have strap-on motors
PSLV – XL: It has strap-on motors

The capacity of payloads:
It can carry the payload of 1750 kg to sun-synchronous polar orbits (SSPO) (Altitude – 600 Kms).
It can carry the payload of 1425 kg to Geosynchronous and Geostationary Orbits (GTO).

About Indian Space Research Organisation (ISRO):

ISRO is the space agency under the Department of Space of Government of India, headquartered in the city of Bengaluru, Karnataka.
Its vision is to harness space technology for national development, while pursuing space science research and planetary exploration.
Antrix Corporation Limited (ACL) is a Marketing arm of ISRO for promotion and commercial exploitation of space products, technical consultancy services and transfer of technologies developed by ISRO.

ISRO Formation

The Indian National Committee for Space Research (INCOSPAR) was established by Jawaharlal Nehru in 1962 under the Department of Atomic Energy (DAE).
Eminent scientist Dr Vikram Sarabhai had a big role in this development. He understood the need for space research and was convinced of the role it can play in helping a nation develop.
INCOSPAR set up the Thumba Equatorial Rocket Launching Station (TERLS) at Thumba, near Thiruvananthapuram at India’s southern tip. TERLS is a spaceport used to launch rockets.
The INCOSPAR became ISRO in 1969.
The Department of Space was created in 1972 and ISRO became a part of it and remains so till date. The Space Department reports directly to the Prime Minister of the country.
During 1975-76, Satellite Instructional Television Experiment (SITE) was conducted. It was hailed as ‘the largest sociological experiment in the world’. It was followed by the ‘Kheda Communications Project (KCP)’, which worked as a field laboratory for need-based and locale-specific program transmission in the state of Gujarat State.
During this phase, the first Indian spacecraft ‘Aryabhata’ was developed and was launched using a Soviet Launcher.
Another major landmark was the development of the first launch vehicle SLV-3 with a capability to place 40 kg in Low Earth Orbit (LEO), which had its first successful flight in 1980.
’80s was the experimental phase wherein, Bhaskara-I & II missions were pioneering steps in the remote sensing area whereas ‘Ariane Passenger Payload Experiment (APPLE)’ became the forerunner for the future communication satellite systems.
Antrix Corporation Limited (ACL) is a Marketing arm of ISRO for promotion and commercial exploitation of space products, technical consultancy services and transfer of technologies developed by ISRO.

About Sun

The Sun is the star at the center of the Solar System. It is a massive hot ball of plasma, inflated and heated by nuclear fusion reactions at its core. Part of this internal energy is emited from the Sun's surface as light, ultraviolet, and infrared radiation, providing most of the energy for life on Earth.

Age of sun is 4.6 billion years;
Diameter of sun is 1.39 million km
Temperature: 6000 °C on the surface and 16 million °C in the core
Speed of rotation: 7179.73 km/hrs. Comparatively, earth’s rotational velocity is 1675Km/hrs.
Period of rotation: 25 days 9 hrs.
Rotation: counter clockwise (when viewed from a long way above Earth’s north pole).
Density: 1.41 times that of water (density of water = 999.97 kg/m³; earth’s overall density is 5.5 times that of water)
The surface gravity of the Sun is 274 m/s2 (28 times the gravity of the Earth). Comparatively, the surface gravity of the earth and moon are 9.8 m/s2 and 1.62 m/s2 respectively.
Mass: equivalent to 3,32,900 Earth masses.
Composition: 98% of the sun is hydrogen & helium.
Most of the solar system’s mass is in the Sun (~99.8%), with most of the remaining mass contained in Jupiter and Saturn. Although the Sun dominates the system by mass, it accounts for only about 2% of the angular momentum due to the differential rotation within the gaseous Sun.

Internal Structure and Atmosphere of the Sun

Internal Structure:

1. Core:

The centre most region of the Sun is known as the core; this is the region where Hydrogen turns into Helium through the nuclear fusion reaction.
With temperatures believed to be reaching more than 15 million degrees Celsius, the core is considered to be the hottest region of the Sun.
When we move towards the outward layers, the density and temperature decrease, and at the centre of the core, it is about 150 g/cm3.

2. Radiative Zone:

Between the core and the convection zone, there lies the radiative zone; by means of radiative diffusion and thermal conduction, the energy in this layer transports outside, which travels in the form of electromagnetic radiation by photons.
Bouncing from particle to particle, photons transfer energy. At the edge of the radiative zone, the density of this layer reduces from 20 g/cm3 to 0.2 g/cm3.

3. Convection Zone:

The outermost layer of the Sun’s interior is known as the convection zone.
This zone uses convection mode to transfer energy.
The temperature at its base is about 2 million degrees Celsius.
The temperature in this zone is low enough for the heavier ions like carbon, oxygen, nitrogen, iron and calcium to hold on to some of their electrons.

Layers of the Atmosphere of the Sun: There are six layers of Sun’s atmosphere

1. Photosphere

The Photosphere has a thickness of about 500 KM, and all the visible light from the Sun comes from this layer.
With temperature coming down to approximately 5500 degrees Celsius, it is said to be the coolest part of the Sun because with an increase in height, the temperature drops.
The phenomenon of Sunspots happens in the Photosphere.

2. Sunspots

The dark spots on the surface of the Sun are known as Sunspots; this happens because the region becomes darker and cooler than the surroundings due to intense magnetic fields on the surface.
The lifetime of Sunspots is generally less; it fluctuates from a few days to a few months.
Umbra is named as the centre of a sunspot, and penumbra is known as the lighter region of the surrounding.
The absence of Sunspots might affect the Earth’s climate because it is supposed that the Sun becomes 1% cooler in the absence of Sunspots.

3. Chromosphere

The Chromosphere is visible as a dim red ring, and it lies just above the Photosphere.
Only during the Solar Eclipses, when the Photosphere is hidden, visible light from the Chromosphere can be seen.
With the increase in height, its temperature increases.

4. Corona

The Corona layer is the outermost layer of the Sun’s atmosphere, and it lies above the Chromosphere.
During a total Solar Eclipse, it can be seen as a white glowing Corona.
Up to 2 million degrees Celsius, the temperature on the Corona spreads, and the reason for it is still unknown.
Coronal mass ejection, Solar winds, and Solar flares are the phenomenon related to Corona.

5. Solar Flares

When magnetic energy is suddenly released, immediate flashy and increased brightness occurs, which is known as Solar flares.
Magnetic irregularities are the reason for their occurrence.
Anywhere between 10 to 20 million degrees Celsius, these are magnetic storms that heat up.

6. Solar Winds

The flow of energised, charged particles at a very high speed is known as Solar wind.
At a temperature equal to 1 million degrees Celsius, the speed of Solar wind is as high as 900 km/s.
It is composed of plasma and generally contains protons, electrons, and alpha particles.