Orbital station-keeping
In astrodynamics orbital stationkeeping is a term used to descibe a particular set of orbital maneuvers used to keep a spacecraft in assigned orbit. It is especially important in satellite communications systems as maintaining proper positions of satellites over long periods of time are crucial for the operatins of those systems.
Stationkeeping manovers require inclusion of a particular delta-v in the mission's delta-v budget. Due to its usually low requirements for propolusive impulses the stationkeeping is usually performed using attitude control system's thrusters.
Stationkeeping is particularly hard for spin-stabilized satellites.
Stationkeeping in LEO
Stationkeeping is necessary to In case of large objects like International Space Station or Mir or Salyut stations the
Stationkeeping in GEO
Taking into consideration a relative long periods of operations of modern GEO satellites the delta-v expended over this period can be substantial. It is therefore crucial for GEO satellites' operators to have the most fuel-efficient propolusion system. Some of the modern satelites are therefore employing a high specific impulse systems like plasma or ion thrusters.