The Indian Space Research Organisation (ISRO) is preparing to perform a crucial maneuver on Saturday, January 6th to place its Aditya-L1 solar mission spacecraft into a halo orbit around the Lagrange Point 1 (L1). This maneuver will mark the culmination of a months-long journey for Aditya-L1 since its launch in November 2023.
Background on the Aditya-L1 Mission
The Aditya-L1 mission aims to study the Sun from a unique vantage point about 1.5 million kilometers from the Earth towards the Sun. The spacecraft carries a suite of instruments to image and study the Sun.
Some key details about the mission:
- Launch Date: November 23, 2023
- Launch Vehicle: ISRO’s Geosynchronous Satellite Launch Vehicle (GSLV)
- Orbit Destination: Halo orbit around Earth-Sun Lagrange Point 1
- Mission Duration: 5-7 years
The L1 Lagrange point is a location in space where the gravitational forces of the Earth and Sun balance out. This allows a spacecraft to orbit the Sun while using little fuel. The halo orbit planned for Aditya-L1 is a three-dimensional corkscrew-shaped orbit that provides stable imaging of the Sun.
Four other solar observation missions are already stationed around the L1 point – NASA’s Advanced Composition Explorer (ACE), NOAA’s DSCOVR, ESA/NASA’s SOHO, and NASA’s Wind spacecraft. Aditya-L1 will join them to provide further solar science and coronal imaging.
Lead-up to Final Orbit Maneuver
After its launch in November, the Aditya-L1 spacecraft progressively raised its orbit using its on-board propulsion system over the span of a month. It undertook several orbit-raising burns to reach closer and closer towards the L1 point.
In the first week of January, the spacecraft finally arrived in the vicinity of the L1 Lagrange point, ready for insertion into the halo orbit. ISRO Chairman S. Somanath revealed that the date for the all-important insertion burn was set for January 6th at 4 PM IST.
On January 5th, ISRO performed calibration tests and confirmed the spacecraft and ground systems were ready for the critical firing the next day. All systems were reported normal, and the spacecraft’s orientation was adjusted in preparation.
The table below summarizes the key milestones over the past month leading up to Saturday’s planned orbit insertion:
|Nov 23, 2023
|Launch of Aditya-L1 spacecraft
|Nov 28 – Dec 15, 2023
|Series of orbit raises to progressively raise apogee
|Early Jan 2023
|Spacecraft arrival near L1 point
|Jan 5, 2023
|Pre-maneuver calibrations and orientation adjustment
|Jan 6, 2023
|Planned insertion burn into halo orbit
The Crucial January 6th Firing
On Saturday at 4 PM IST, ISRO will command the spacecraft to fire its engines for about 5 minutes. This firing aims to reduce the spacecraft’s velocity just enough to allow the pull of the Sun’s and Earth’s gravity to capture it into the intended halo orbit.
ISRO spent years planning this maneuver using complex simulations and models. If the burn time or orientation is off even slightly, the spacecraft could drift away into an improper orbit from which recovery may not be possible. Therefore, the moment marks a tense, high-stakes operation for the missions scientists.
However, ISRO officials have expressed full confidence in the meticulous planning and the capability of the spacecraft’s systems. Mission Director Dr. Nigar Shaji said “We have done the simulations 1000 times” and Chairman Somanath assured even in a sub-optimal case, they could re-orient the craft.
If the firing achieves at least 90% of the planned objective, the spacecraft should stabilize into an acceptable orbit meeting mission requirements. Some extra maneuvering may still be needed over the coming weeks to fine-tune the orbit.
The Science Goals of the Mission
Once established in its halo orbit, Aditya-L1 will unfold its instrument payload and begin its 5+ year science mission studying the Sun.
The key science goals and instruments of Aditya-L1 include:
- Produce near real-time full disk images of the Sun every few seconds in multiple wavelengths using the Visible Emission Line Coronagraph (VELC)
- Measure properties of the solar corona and dynamics using the Solar Ultraviolet Imaging Telescope (SUIT)
- Detect major solar eruptions like coronal mass ejections with the Solar Low Frequency Radio Spectrometer (SLFRS)
- Study the particle flux emanating from the Sun with the Plasma Analyser Package for Aditya (PAPA) and Solar Low Energy X-ray Spectrometer (SoLEXS)
These instruments collectively aim to shed light on long-standing mysteries regarding the Sun’s corona, solar storms, and the solar wind. The data will help improve space weather forecasting and predictions of solar storms that can impact satellite technology on Earth. Being a unique mission viewing the Sun from the L1 vantage point, Aditya-L1 is expected to provide observations not possible from orbits near the Earth or ground-based observatories.
What Next After Orbit Insertion?
If Saturday’s crucial orbit insertion maneuver goes as planned, it will take a few weeks for controllers to check all systems and finalize some orbit adjustment burns. Once the spacecraft is deemed ready, the mission will enter the science phase.
The Visible Emission Line Coronagraph (VELC) instrument will turn on first and should immediately start sending back stunning images and videos of the Sun’s atmosphere. ISRO has said it will swiftly release this footage publicly.
Over 2024, the other instruments will sequentially power on and calibrate themselves before starting regular observations. The mission team will also release periodic updates showcasing key results and discoveries.
Further ahead, NASA has an agreement to collaborate with ISRO to use Aditya-L1’s coronagraph observations to support its own Parker Solar Probe mission. Cross-inputs between the two missions observing the Sun from different locations could reveal new findings faster.
In the years to come, Aditya-L1 is sure to fundamentally transform our understanding of the Sun while also raising India’s science and technology prowess globally. But first, all eyes are on the crucial firing on Saturday that will set the spacecraft on course for its groundbreaking solar science mission.
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