ISRO's Aditya-L1 Spacecraft Commences its Journey Towards the Sun-Earth L1 Point

ISRO's Aditya-L1 Spacecraft Commences its Journey Towards the Sun-Earth L1 Point

ISRO's Aditya-L1 mission, launched on September 2, 2023, is India's first mission dedicated to studying the Sun, specifically the photosphere, chromosphere, and corona of the Sun. The spacecraft commenced its journey to its final destination, the Sun-Earth Lagrange’s Point 1 (L1), on September 18, 2023.

Lagrange points, also known as libration points, are unique locations in space where the gravitational force of two massive bodies (like the Sun and Earth) precisely equals the centripetal force required for a small object (like spacecraft) to move with them. This makes Lagrange points an excellent location for spacecraft as orbit corrections and hence fuel requirements, needed to maintain the desired orbit, are kept at a minimum.

For any combination of two orbital bodies (like Sun-Earth and Earth-Moon systems), there are five Lagrange points (L1 to L5), all in the orbital plane of the two large bodies (figure-1). The three points - L1, L2, and L3 are dynamically unstable and lie on the line through the centres of the two large bodies, while the remaining two points - L4 and L5 are stable points and each acts as the third vertex of an equilateral triangle formed with the centres of the two large bodies.

Figure 1: Lagrange Points

L1 is particularly significant because it is situated between the two primaries (the Sun and Earth), making it an ideal location for spacecraft because it allows continuous observation of primary bodies, continuous communication with Earth, and an unobstructed view of celestial bodies. These orbits are well-suited for scientific missions like Aditya which will act like a solar observatory around L1 and communication to Earth.

ISRO's Aditya-L1 will operate in a ‘Halo orbit’ around the Sun-Earth L1 point, located approximately 1.5 million kilometers from Earth. Halo orbits are periodic, three-dimensional orbits around a Lagrange Point (L1, L2, or L3) and involve an out-of-plane motion component relative to the primary bodies. The orbit is large enough in size to be continuously viewed from Earth and would appear to form a halo around the Lagrange Points (here L1 for Aditya L1).

Various past missions have utilized the Sun-Earth L1 point, including the International Sun-Earth Explorer (ISEE-3), the Genesis mission, ESA's LISA Pathfinder, China's Chang'e 5 lunar orbiter, and NASA's Gravity Recovery and Interior Recovery (GRAIL) mission. These missions have contributed to our understanding of space and our ability to monitor space weather events.

Several operational spacecrafts are currently stationed at the Sun-Earth L1 point as provided in table-1. These spacecraft at Sun-Earth L1 point provide vital early warnings on adverse space weather events that help protect orbiting space assets and ground-based infrastructure.

Click here to learn more about ISRO's Aditya-L1 Solar Mission.

Publisher: SatNow
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GNSS Constellations - A list of all GNSS satellites by constellations


Satellite NameOrbit Date
BeiDou-3 G4Geostationary Orbit (GEO)17 May, 2023
BeiDou-3 G2Geostationary Orbit (GEO)09 Mar, 2020
Compass-IGSO7Inclined Geosynchronous Orbit (IGSO)09 Feb, 2020
BeiDou-3 M19Medium Earth Orbit (MEO)16 Dec, 2019
BeiDou-3 M20Medium Earth Orbit (MEO)16 Dec, 2019
BeiDou-3 M21Medium Earth Orbit (MEO)23 Nov, 2019
BeiDou-3 M22Medium Earth Orbit (MEO)23 Nov, 2019
BeiDou-3 I3Inclined Geosynchronous Orbit (IGSO)04 Nov, 2019
BeiDou-3 M23Medium Earth Orbit (MEO)22 Sep, 2019
BeiDou-3 M24Medium Earth Orbit (MEO)22 Sep, 2019


Satellite NameOrbit Date
GSAT0223MEO - Near-Circular05 Dec, 2021
GSAT0224MEO - Near-Circular05 Dec, 2021
GSAT0219MEO - Near-Circular25 Jul, 2018
GSAT0220MEO - Near-Circular25 Jul, 2018
GSAT0221MEO - Near-Circular25 Jul, 2018
GSAT0222MEO - Near-Circular25 Jul, 2018
GSAT0215MEO - Near-Circular12 Dec, 2017
GSAT0216MEO - Near-Circular12 Dec, 2017
GSAT0217MEO - Near-Circular12 Dec, 2017
GSAT0218MEO - Near-Circular12 Dec, 2017


Satellite NameOrbit Date
Kosmos 2569--07 Aug, 2023
Kosmos 2564--28 Nov, 2022
Kosmos 2559--10 Oct, 2022
Kosmos 2557--07 Jul, 2022
Kosmos 2547--25 Oct, 2020
Kosmos 2545--16 Mar, 2020
Kosmos 2544--11 Dec, 2019
Kosmos 2534--27 May, 2019
Kosmos 2529--03 Nov, 2018
Kosmos 2527--16 Jun, 2018


Satellite NameOrbit Date
Navstar 82Medium Earth Orbit19 Jan, 2023
Navstar 81Medium Earth Orbit17 Jun, 2021
Navstar 78Medium Earth Orbit22 Aug, 2019
Navstar 77Medium Earth Orbit23 Dec, 2018
Navstar 76Medium Earth Orbit05 Feb, 2016
Navstar 75Medium Earth Orbit31 Oct, 2015
Navstar 74Medium Earth Orbit15 Jul, 2015
Navstar 73Medium Earth Orbit25 Mar, 2015
Navstar 72Medium Earth Orbit29 Oct, 2014
Navstar 71Medium Earth Orbit02 Aug, 2014


Satellite NameOrbit Date
NVS-01Geostationary Orbit (GEO)29 May, 2023
IRNSS-1IInclined Geosynchronous Orbit (IGSO)12 Apr, 2018
IRNSS-1HSub Geosynchronous Transfer Orbit (Sub-GTO)31 Aug, 2017
IRNSS-1GGeostationary Orbit (GEO)28 Apr, 2016
IRNSS-1FGeostationary Orbit (GEO)10 Mar, 2016
IRNSS-1EGeosynchronous Orbit (IGSO)20 Jan, 2016
IRNSS-1DInclined Geosynchronous Orbit (IGSO)28 Mar, 2015
IRNSS-1CGeostationary Orbit (GEO)16 Oct, 2014
IRNSS-1BInclined Geosynchronous Orbit (IGSO)04 Apr, 2014
IRNSS-1AInclined Geosynchronous Orbit (IGSO)01 Jul, 2013