Preparations in the final phase for the launch of PSLV-C57/Aditya-L1 Mission.
| Photo Credit: PTI

The countdown for the launch of India’s first solar observatory mission, Aditya-L1 has commenced at the Satish Dhawan Space Centre in Sriharikota.

“The countdown leading to the launch at 11:50 Hrs. IST on September 2, 2023 has commended,” ISRO posted on X (formerly Twitter).

The Aditya-L1 spacecraft is scheduled to be launched by the Polar Satellite Launch Vehicle (PSLV) on September 2, 2023, at 11:50 a.m. from Sriharikota.

This is the 59th flight of the PSLV and the 25th mission using the PSLV-XL configuration.

The PSLV will launch Aditya-L1 spacecraft in a highly eccentric Earth bound orbit.

According to ISRO 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 of observing the solar activities and its 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,” states the Aditya L1 mission profile.

The suits of Aditya L1 payloads are expected to provide the most crucial information to understand the problem of coronal heating, coronal mass ejection, pre-flare and flare activities and their characteristics, dynamics of space weather, propagation of particles and fields etc.

The seven payloads onboard the satellite is Visible Emission Line Coronagraph(VELC), Solar Ultraviolet Imaging Telescope (SUIT), Solar Low Energy X-ray Spectrometer (SoLEXS), High Energy L1 Orbiting X-ray Spectrometer(HEL1OS), Aditya Solar wind Particle Experiment(ASPEX), Plasma Analyser Package For Aditya (PAPA) and Advanced Tri-axial High Resolution Digital Magnetometers.

The launch of Aditya-L1 comes days after the space agency created history making India only the fourth country to successfully land on the moon and first to land near the lunar south pole.

Aditya L1 onboard the PSLV-C57 the Satish Dhawan Space Centre in Sriharikota on September 1, 2023 on the eve of its launch. Photo: X/@ISRO via PTI

India’s first solar observatory mission, named Aditya-L1, will be launched onboard the Polar Satellite Launch Vehicle (PSLV) from the Satish Dhawan Space Centre in Sriharikota at 11.50 am on Saturday.

On Friday, the Indian Space Research Organisation (ISRO) commenced the 23-hour 40-minute countdown for the launch of the Aditya-L1 mission.

Approximately sixty-three minutes after liftoff, the satellite separation is expected to take place as the PSLV will launch the Aditya-L1 spacecraft into a highly eccentric earth-bound orbit at around 12.53 pm.

This PSLV-C57/Aditya-L1 mission can be counted as one of the longest missions involving ISRO’s workhorse launch vehicle. However, the longest of the PSLV missions is still the 2016 PSLV-C35 mission which was completed two hours, 15 minutes and 33 seconds after lift-off.

Long journey

Following the launch, Aditya-L1 will stay in earth-bound orbits for 16 days, during which it will undergo five manoeuvres to gain the necessary velocity for its journey.

“Subsequently, Aditya-L1 undergoes a Trans-Lagrangian1 insertion manoeuvre, marking the beginning of its 110-day trajectory to the destination around the L1 Lagrange point. Upon arrival at the L1 point, another manoeuvre binds Aditya-L1 to an orbit around L1, a balanced gravitational location between the Earth and the Sun,” ISRO said.

Aditya-L1 will stay approximately 1.5 million km away from the earth, directed towards the sun; this is about 1% of the distance between the earth and the sun.

Studying the solar corona

The Aditya L-1 payloads are expected to provide crucial information to understand the problem of coronal heating, coronal mass ejection, pre-flare and flare activities and their characteristics, dynamics of space weather, propagation of particles and fields etc.

The seven payloads onboard the satellite are: Visible Emission Line Coronagraph (VELC), Solar Ultraviolet Imaging Telescope (SUIT), Solar Low Energy X-ray Spectrometer (SoLEXS), High Energy L1 Orbiting x-ray Spectrometer (HEL1OS), Aditya Solar wind Particle Experiment (ASPEX), Plasma Analyser Package for Aditya (PAPA), and Advanced Tri-axial High Resolution Digital Magnetometers.

The primary payload is VELC, which was developed by the Indian Institute of Astrophysics (IIA), Bengaluru and is designed to study the solar corona and the dynamics of coronal mass ejections.

The Aditya-L1 satellite placed in the halo orbit around the L1 point has a major advantage of continuously viewing the sun without any occultation or eclipse. It is expected to provide a greater advantage in observing the solar activities continuously.

Tracking solar quakes

“There are certain activities which take place around the sun which we call solar quakes. In the aftermath of these solar quakes, a lot of energetic material from the sun is thrown out. Some of them can be directed towards the earth and they can travel at a maximum speed of 3,000 km per hour and reach the near-earth space within 15 hours,” Ramesh R., the principal investigator of the VELC payload, told The Hindu.

Prof. Ramesh added that once the energetic material reaches the earth, it may not cause any physical damage, but it does have the capability to cripple life on earth.

“Our present-day life scenario depends very much on the stationary satellites which are parked in space be it for our internet connectivity, cell phone or TV connectivity. These charged particle clouds can engulf the satellites and damage all the electronics on board the satellites. Hence, we do not know when the solar quakes will happen, it can happen any time of the day so it is very essential to observe the sun on a 24-hour basis and carry out observations,” Prof. Ramesh added.