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Low lunar orbit (LLO) is an orbit below 100 km (62 mi) altitude. These have a period of about 2 hours. [ 2 ] They are of particular interest in the exploration of the Moon , but suffer from gravitational perturbations that make most unstable, and leave only a few orbital trajectories possible for indefinite frozen orbits .
Low-energy transfers to the Moon were first demonstrated in 1991 by the Japanese spacecraft Hiten, which was designed to swing by the Moon but not to enter orbit.The Hagoromo subsatellite was released by Hiten on its first swing-by and may have successfully entered lunar orbit, but suffered a communications failure.
The lunar DRO is a high lunar orbit with a radius of approximately 61,500 km. [24] This was proposed [by whom?] in 2017 as a possible orbit for the Lunar Gateway space station, outside Earth-Moon L1 and L2. [20] Decaying orbit: A decaying orbit is an orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. [1]
Low orbits. Through a study of many lunar orbiting satellites, scientists have discovered that most low lunar orbits (LLO) are unstable. [5] Four frozen lunar orbits have been identified at 27°, 50°, 76°, and 86° inclination. NASA described this in 2006: Lunar mascons make most low lunar orbits unstable ... As a satellite passes 50 or 60 ...
The semi-major axis of the geocentric lunar orbit, called the lunar distance, is approximately 400,000 km (250,000 miles or 1.28 light-seconds), comparable to going around Earth 9.5 times. [178] The Moon makes a complete orbit around Earth with respect to the fixed stars, its sidereal period, about once every 27.3 days.
Ballistic capture is a low energy method for a spacecraft to achieve an orbit around a distant planet or moon with no fuel required to go into orbit. In the ideal case, the transfer is ballistic (requiring zero Delta-v) after launch.
Ten Lunar Modules were launched into space. Of these, six were landed by humans on the Moon from 1969 to 1972. The first two flown were tests in low Earth orbit: Apollo 5, without a crew; and Apollo 9 with a crew. A third test flight in low lunar orbit was Apollo 10, a dress rehearsal for the first landing, conducted on Apollo 11.