Phased Orbit
The orbit of a satellite is phased when the satellite passes by again exactly on the same trace on the ground; this is possible when the period of the satellite and the duration of the sidereal day are commensurable (the duration of the sidereal day corresponds exactly to an integer of periods of the satellite), or more generally when an integer of periods of the satellite correspond to an integer of sidereal days.
Observation of the Earth
Many satellites of observation of the Earth traverse a phased orbit (SPOT, TOPEX-POSEIDON, JASON-1…). This makes it possible to regularly observe the ground under comparable conditions (illumination, incidence…), especially when the orbit is at the same time phased and heliosynchronous and thus to facilitate the detection of the evolutions.This strategy of observation involves sometimes disadvantages, as impossibility of detecting events which occur with one multiple period of the period of observation, or of which certain periods correspond to the period of observation (tide, for example): this phenomenon is often called Crènelage , fold of spectrum , or aliasing .
See too
| Random links: | Alexey Ignashov | War of Fishing | Pierre Chaillan | Rotrou II of the Pole | Literature sénégalaise | Aporia |