On December 30, astronomer Jonathan McDowell posted on X.com: “The deserted Chandrayaan-3 The propulsion module, left in a 125000 x 305000 km orbit in 2024, had a little bit of a tussle with the Moon in November and has now been present in a 365000 x 983000 km x 22 deg orbit”.
Dr. McDowell is well-known for, amongst different issues, publishing Jonathan’s House Report, “an irregular e-newsletter which makes an attempt to supply an in depth and pedantic historic document of the house age” and for sustaining the ‘Normal Catalog of Synthetic House Objects’.
tug of battle
His put up describes a standard drawback in spaceflight: as soon as you permit a spacecraft in a really massive and lopsided orbit across the Earth that comes anyplace close to the moon’s path, the moon’s gravity can maintain nudging it in methods which are onerous to foretell far upfront.
“Moon-orbit-crossing” in his put up means the item’s orbit across the earth reaches out to distances corresponding to the moon’s distance. In consequence at some factors the item and the moon can go comparatively shut to one another. When that occurs, the moon’s gravity issues loads.
In low-earth orbit, i.e. 150-2,000 km above sea degree, the earth’s gravity dominates and the movement of satellites right here is pretty common. However if you get nearer to the moon, you are successfully in a three-body scenario: the earth pulls, the moon pulls, and an object in between that is affected by each their pulls strikes rapidly by means of areas the place the steadiness of these pulls adjustments.
In these programs, small variations in timing or place can result in massive variations later. That’s what Dr. McDowell means “chaotic”. The orbit continues to be ruled by the legal guidelines of physics however the underlying equations are very tough to resolve.
This was additionally the premise of the science fiction guide and later Netflix present. ‘3 Physique Drawback’An alien species inhabited a world in a system with three suns orbiting one another, repeatedly resulting in durations of local weather chaos, The three-body drawback asks how three plenty transfer when every attracts the others by gravity, In classical mechanics, this drawback does not have a normal closed-form resolution, that means there isn’t any single formulation with which you’ll be able to predict how the system will evolve for all potential beginning positions, speeds, and much,
A looping path
The Chandrayaan-2 mission led to partial failure when its lunar lander crashed on the moon’s floor in 2019. However because it had efficiently launched an orbital module, which continued to orbit the moon, the Chandrayaan-3 mission solely consisted of a propulsion module, a lander, and a rover.
After the lander and rover descended on the moon in August 2023, the Indian House Analysis Group (ISRO) moved the propulsion module to a 125,000 x 305,000 km orbit across the earth in October. These two numbers are the distances from the earth on the closest level (perigee) and farthest level (apogee) of the orbit.
So the propulsion module was looping across the Earth on a extremely elliptical path: it got here as shut as about 125,000 km, then swung out to about 305,000 km, approaching the moon’s common distance (~384,000 km). Meaning it spent a few of its time within the moon’s gravitational neighborhood.
The moon’s kick
When Dr. McDowell says it had “a tussle with the moon in November”, he means the propulsion module had a comparatively shut go by the moon. Throughout an in depth go, the moon’s gravity can kick, or all of a sudden change, the item’s velocity and course relative to the Earth. This isn’t like friction or a collision however a purely gravitational interplay. Relying on the geometry, the kick can elevate the orbit, decrease it, tilt it or change its form.
Based on a ISRO assertion in November, the propulsion module entered the moon’s “sphere of affect” on November 4 and exited it on November 14. The group stated it tracked the ‘occasion’ utilizing the Indian Deep House Community (IDSN), a group of antennae close to Bengaluru that, along with information obtained by related floor stations operated by NASA and different house businesses, displays Indian property in house.
Whereas it was within the moon’s sphere of affect, the propulsion module flew by the moon twice: on November 6 it got here inside 3,740 km of the lunar floor and on November 11 inside 4,537 km.
After this encounter, the orbit of the propulsion module modified in 3 ways. First, it grew to become a lot bigger general. Based on ISRO the apogee jumped to 727,000 km; Dr. McDowell wrote in his put up on December 30 that it was 983,000 km excessive. Both quantity is effectively past the moon’s distance and an indication that the moon’s pull added (or rearranged) orbital power within the earth’s body.
Second, the brand new orbit has a special form and orientation. ISRO concluded the perigee to be 409,000 km and Dr. McDowell, 365,000 km. That’s, the propulsion module now not comes again anyplace close to 125,000 km; it stays excessive nearly on a regular basis. And third, the orbit grew to become noticeably tilted, by 22º, relative to the Earth’s equator. This occurred as a result of the moon’s gravity pulled the module in a course that wasn’t completely aligned with its present movement and orbital aircraft. In consequence the module’s angular momentum vector modified.
Very completely different orbit
Per the assertion, ISRO took “particular care … to observe its trajectory” and its proximity to different house objects. “The general satellite tv for pc efficiency was regular in the course of the flyby and no shut method was skilled with the opposite lunar orbiters. This occasion garnered useful insights and expertise from mission planning, operations, flight dynamics views, and particularly enhanced the understanding of disturbance torque results.”
In sum, ISRO left the Chandrayaan-3 propulsion module in a large earth orbit that grazed the moon’s neighbourhood. In November 2025, the timing lined up such that the moon handed shut sufficient to strongly tug on the propulsion module. This reshaped its orbit, pushing it into a better, extra tilted, and extra excessive ellipse. In consequence, monitoring groups now discovered it with a really completely different set of orbital parameters.
In his put up, Dr. McDowell credited newbie astronomer Sam Deen, astronomer Luca Buzzi, and Invoice Grey, who developed notable software program to trace near-earth objects, “for determining that the suspected asteroid CE1M9G2 … was truly Chandrayaan-3”.
Revealed – December 30, 2025 08:37 am IST