Sunshine moment as PSLV orbits Aditya-L1 to study Sun

 SRIHARIKOTA: India's workhorse rocket PSLV successfully put its Aditya-L1 spacecraft to study the Sun into an intermediate orbit or low earth orbit on Saturday afternoon in textbook style.

From there, begins a long 125-day journey for Aditya-L1-suitably named after the Sun God in Hindu mythology-as it has to travel about 1.5 million km to its intended slot to study the Sun.

Speaking about the success, the Chairman of the Indian Space Research Organisation (ISRO), Dr. S. Somanath, said: "The Aditya-L1 spacecraft has been injected into its intended orbit. It is a different mission. From now on, Aditya-L1 will start its 125-day journey to L1 (Lagrange Point 1)."

Union Minister of State Dr. Jitendra Singh, who witnessed the launch here, said: "It is a sunshine moment for India."

"Once the Aditya-L1 reaches the L1 point, it will be a great asset for the scientific community," said Nigar Shaji, project director of the Aditya-L1.

At approximately 11.50 a.m., the Polar Satellite Launch Vehicle-C57 (PSLV-C57) rose into the sky after breaking free from the second launch pad here at Satish Dhawan Space Centre.

Slowly rising up towards the skies with a thick orange flame at its tail, the rocket gained speed with a sound resembling rolling thunder and went up and up, leaving a thick plume while the people assembled at the viewers' gallery cheered and clapped their hands with pride.

Interestingly, this was one of the longest missions for the rocket as well as for the Indian Space Research Organisation (ISRO).

About 63 minutes after liftoff, the rocket ejected Aditya-L1, and the whole mission came to an end about 73 minutes after the passivation of the fourth stage.

"We have to meet the argument of the perigee of the satellite. For that, we are following two burn strategies for the fourth stage. After the first burn, there is a long coasting to achieve the argument of perigee that occurs naturally," Dr. S. Unnikrishnan, Director, Vikram Sarabhai Space Centre (VSSC), told IANS about the long flight duration.

The flight plan included switching off the rocket's fourth stage twice and allowing it to coast for about 30 minutes-26 minutes after the first cutoff and about 3 minutes after the second cutoff.

Put into low earth orbit (LEO), Aditya-L1's orbit will initially be elliptical. As the spacecraft travels towards Lagrange Point (L1), it will exit the earth's gravitational sphere of influence (SOI).

After exit from SOI, the cruise phase will start, and subsequently the spacecraft will be injected into a large halo orbit around L1-the point where the gravitational pull of two large bodies-the Sun and Earth-will be equal, and hence the spacecraft will not gravitate towards any one of the planets.

The total travel time from launch to L1 would take about four months for Aditya-L1, and the distance would be about 1.5 million km from the Earth.

The distance between the Earth and the Moon is about 3,84,000 km.

"A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the sun without any occultation or eclipse." This will provide a greater advantage of observing the solar activities and their effect on space weather in real time," the ISRO said.

In its normal configuration, PSLV is a four-stage, expendable rocket powered by solid and liquid fuels, with six booster motors strapped on to the first stage to give higher thrust during the initial flight moments.

The rocket that flew on Saturday was the XL variant, with longer strap-on motors.

Interestingly, the XL variant rocket was used for the first time for India's first interplanetary mission, the Chandrayaan-1, or Moon Mission-1. Later, the rocket was used for Chandrayaan-2 and the Mars Mission/Mars Orbiter Mission.

And Saturday's PSLV-XL variant is flying for the 25th time on another interplanetary mission.

The Saturday rocketing comes soon after India landed on the moon on August 23, with its lander safely landing on the lunar soil in textbook style.

Later, the rover rolled down and started doing experiments.

Be that as it may, the Indian space agency said, the Aditya-L1 spacecraft carries seven payloads to observe the photosphere, chromosphere, and the outermost layers of the sun (the corona) using electromagnetic, 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," ISRO said.

Aditya-L1's seven payloads are expected to provide the most crucial information to understand the problems of coronal heating, coronal mass ejection, pre-flare and flare activities and their characteristics, the dynamics of space weather, the propagation of particles and fields, and others, the Indian space agency said.

The ISRO said the major science objectives of the Aditya-L1 mission are: study of solar upper atmospheric (chromosphere and corona) dynamics; study of chromospheric and coronal heating; physics of the partially ionised plasma; and initiation of coronal mass ejections and flares.

It will also observe the in-situ particle and plasma environment, providing data for the study of particle dynamics from the sun.

Other objectives are the physics of the solar corona and its heating mechanism, the diagnostics of the coronal and coronal loop plasma, Temperature, velocity, and density, development, dynamics, and origin of coronal mass ejections (CME), to 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, and the drivers for space weather (origin, composition, and dynamics of solar wind).

According to ISRO, the Sun, estimated to be 4.5 billion years old, is a hot, glowing ball of hydrogen and helium gases and is the source of energy for the solar system.

"The gravity of the sun holds all the objects of the solar system together. At the central region of the sun, known as the core', the temperature can reach as high as 15 million degrees Celsius," it said.

At this temperature, a process called nuclear fusion takes place in the core, which powers the sun. The visible surface of the sun, known as the photosphere, is relatively cool and has a temperature of about 5,500 degrees Celsius, the ISRO said.

The Sun is the nearest star and therefore can be studied in much more detail as compared to other stars. By studying the sun, we can learn much more about stars in our Milky Way as well as about stars in various other galaxies, the ISRO said.

The sun is a very dynamic star that extends much beyond what we see. It shows several eruptive phenomena and releases immense amounts of energy in the solar system. If such explosive solar phenomena are directed towards the earth, they could cause various types of disturbances in the near-earth space environment.

Various spacecraft and communication systems are prone to such disturbances, and therefore, early warning of such events is important for taking corrective measures beforehand.

In addition to these, if an astronaut is directly exposed to such explosive phenomena, he or she would be in danger. The various thermal and magnetic phenomena on the sun are of extreme nature.

Thus, the sun also provides a good natural laboratory to understand those phenomena that cannot be directly studied in the lab.

The Indian space agency said all seven payloads carried by Aditya-L1 were indigenously developed by different laboratories in the country in close coordination with it. (IANS)

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