Orbit determination

With more or better observations, the accuracy of the orbit determination process also improves, and fewer "false alarms" result.

For the United States and partner countries, to the extent that optical and radar resources allow, the Joint Space Operations Center gathers observations of all objects in Earth orbit.

Orbit determination has a long history, beginning with the prehistoric discovery of the planets and subsequent attempts to predict their motions.

Johannes Kepler used Tycho Brahe's careful observations of Mars to deduce the elliptical shape of its orbit and its orientation in space, deriving his three laws of planetary motion in the process.

Another milestone in orbit determination was Carl Friedrich Gauss's assistance in the "recovery" of the dwarf planet Ceres in 1801.

The theory of orbit determination has subsequently been developed to the point where today it is applied in GPS receivers as well as the tracking and cataloguing of newly observed minor planets.

In order to determine the unknown orbit of a body, some observations of its motion with time are required.

However, the returned signal strength from radar decreases rapidly, as the inverse fourth power of the range to the object.

Larger apertures permit tracking of transponders on interplanetary spacecraft throughout the solar system, and radar astronomy of natural bodies.

If two such observations are available, along with the time difference between them, the orbit can be determined using Lambert's method, invented in the 18th century.

Even if no distance information is available, an orbit can still be determined if three or more observations of the body's right ascension and declination have been made.

Gauss's method, made famous in his 1801 "recovery" of the first lost minor planet, Ceres, has been subsequently polished.