The satellite revisit period is the time elapsed between observations of the same point on Earth by a
satellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
.
It depends on the satellite's
orbit
In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...
, target location, and
swath
A small waterplane area twin hull, better known by the acronym SWATH, is a catamaran design that minimizes hull cross section area at the sea's surface. Minimizing the ship's volume near the surface area of the sea, where wave energy is located ...
of the sensor.
"Revisit" is related to the same
ground trace
A satellite ground track or satellite ground trace is the path on the surface of a planet directly below a satellite's trajectory. It is also known as a suborbital track or subsatellite track, and is the vertical projection of the satellite's ...
, a projection of the satellite's orbit on to the Earth. Revisit requires a very close repeat of the ground trace. In the case of
polar orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of abo ...
or
highly inclined low-Earth-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. Most of the artificial objects in outer space are in LEO, peaking in number at an a ...
reconnaissance satellite
A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications.
The ...
s, the sensor must have the variable swath, to look longitudinally (east-west, or sideways) at a target, in addition to direct overflight observation, looking
nadir
The nadir is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
The direction opposite of the nadir is the zenith.
Et ...
.
In the case of the
Israel
Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...
i
EROS
Eros (, ; ) is the Greek god of love and sex. The Romans referred to him as Cupid or Amor. In the earliest account, he is a primordial god, while in later accounts he is the child of Aphrodite.
He is usually presented as a handsome young ma ...
Earth observation satellite, the ground trace repeat is 15 days, but the actual revisit time is 3 days, because of the swath ability of the camera payload.
See also
*
Orbit period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets, ...
*
Satellite watching
Satellite watching or satellite spotting is a hobby which consists of the observation and tracking of artificial satellites that are orbiting Earth. People with this hobby are variously called satellite watchers, trackers, spotters, observers, ...
, spotting satellites in the sky as they pass
References
{{DEFAULTSORT:Satellite Revisit
Satellites
Orbits