Japanese Lunar Exploration Program 2007, after being delayed several times. SELENE-2, Japan's first lunar lander and rover, is expected to be launched in the 2020s. The program also includes a lunar sample return mission (SELENE-3), a mission to Mars to collect data for future manned expeditions (MELOS), participation in the Mars international sample return mission, and an advanced lander for future human missions to the Moon. The eventual goal is to participate in an international lunar outpost program, in which Japanese crews would stay on the lunar surface for a prolonged period of time and promote scientific research and environment utilization. SELENE (Selenological and
Orbital station-keeping track it is also necessary to make out-of-plane manoeuvres to compensate for the inclination change caused by Sun/Moon gravitation. These are executed as thruster burns orthogonal to the orbital plane. For Sun-synchronous spacecraft having a constant geometry relative to the Sun, the inclination change due to the solar gravitation is particularly large; a delta-v in the order of 1–2 m/s per year can be needed to keep the inclination constant. For geostationary spacecraft, thruster burns orthogonal to the orbital plane must be executed to compensate for the effect of the lunar/solar gravitation that perturbs the orbit pole with typically 0.85