plural of heliosynchronous orbit

A satellite orbit around the Earth within the altitude range of 200 - 2000 km, in which a satellite can communicate with Earth with a small time lag and energy consumption. Abbreviation: LEO.

(space flight) A lunar-resonant orbit about the Earth with a period of 1/2 that of the Moon's (P/2 is an orbit that is approximately a fortnight long)

(science fiction) A satellite or space station, found in many different works of science fiction, meant to defend a planet against attack from space.

(algebra) A theorem which states that for each element of a given set that a given group acts on, there is a natural bijection between the orbit of that element and the cosets of the stabilizer subgroup with respect to that element.

(of a black hole) Synonym of photon sphere

plural of orbital quantum number

(astronomy) The sidereal year of a planet. (I.e., in the definition for "sidereal year", replace "Earth" by the given planet.)

(inorganic chemistry) A complex, typically of a transition element, in which the hybridization of the central metal atom utilizes d orbitals from the shell inside that of the outermost occupied shell

azimuthal quantum number