Lunar orbit

[2] Gravitational anomalies slightly distorting the orbits of some Lunar Orbiters led to the discovery of mass concentrations (dubbed mascons) beneath the lunar surface caused by large impacting bodies at some remote time in the past.

They can cause a plumb bob to hang about a third of a degree off vertical, pointing toward the mascon, and increase the force of gravity by one-half percent.

[2] The Apollo 11 first manned landing mission employed the first attempt to correct for the perturbation effect (the frozen orbits were not known at that time).

[citation needed] Since 2022 (CAPSTONE) near-rectilinear halo orbits, using as well a Lagrange point, have been used and are planned to be employed by the Lunar Gateway.

[8] The Soviet Union sent the first spacecraft to the vicinity of the Moon (or any extraterrestrial object), the robotic vehicle Luna 1, on January 4, 1959.

[12] A follow-on mission, Luna 11, was launched on August 24, 1966, and studied lunar gravitational anomalies, radiation and solar wind measurements.

Five such spacecraft were launched over a period of thirteen months, all of which successfully mapped the Moon, primarily for the purpose of finding suitable Apollo program landing sites.

The LM began its landing sequence with a Descent Orbit Insertion (DOI) burn to lower their periapsis to about 50,000 feet (15 km; 8.2 nmi), chosen to avoid hitting lunar mountains reaching heights of 20,000 feet (6.1 km; 3.3 nmi).

After the second landing mission, the procedure was changed on Apollo 14 to save more of the LM fuel for its powered descent, by using the CSM's fuel to perform the DOI burn, and later raising its periapsis back to a circular orbit after the LM had made its landing.

Orion capsule of Artemis 1 above the Moon in December 2022.
Lunar Module Eagle in lunar orbit during Apollo 11 , July 1969
An example of a halo orbit at the second lunar lagrange point.
Near-rectilinear halo orbit ( NRHO ) in cislunar space, as illustrated by A.I. Solutions, Inc. using the FreeFlyer software.
Overview of NRHOs around the Moon
Animation of LRO trajectory around Earth. Using a direct transfer, it arrived on moon in four and a half days
Lunar Reconnaissance Orbiter · Earth · Moon
Chandrayaan-3 's trajectory included multiple orbit raising maneuvers to get to the Moon
SLIM 's trajectory included low energy transfer
First image of Earth from around another astronomical object (the Moon), and first picture of both Earth and the Moon from space, by Lunar Orbiter 1 (not to be confused with the later Earthrise image). [ 9 ] [ 10 ]