# Calculate Satellite Speed and Orbital Time

Calculator for the velocity of a satellite and the time it takes for one orbit. Both values only depend on the distance between the satellite and the earth or its center. Satellites have an elliptical orbit, this can also be a circular orbit. In the case of a circular orbit, the distance is always the same; in the case of an elliptical orbit, the relevant value is the semimajor axis. The closer a satellite is to earth, the faster it has to be to avoid falling down. Satellites that are always above the same place on earth have a geostationary orbit 35794 kilometers above the earth.

The formulas for the calculation are:

Time T = √ 4 π² a³ / (GM)

Velocity v = √ GM / a

with distance or semimajor axis a, gravitational constant G and mass of the earth M, provided that the mass of the satellite is negligible compared to the mass of the earth.

Please enter the altitude (height) above earth h or distance a to calculate speed and orbital period. The radius of the earth is calculated at 6370 kilometers.

Example: the ISS at an altitude of 400 kilometers is traveling at a speed of 27623.5 kilometers per hour and needs a little more than one and a half hours to orbit the earth.

The word satellite is of Latin origin and means something like companion. In the astronomical sense, it is an object that orbits another. This may be a natural object, so the moon is a satellite of the Earth. Planets tend not to be called satellites of their stars, but there are galaxies with satellite galaxies. The word is best known from space travel for artificial objects that are launched into space by humans and orbit the earth. Satellite orbits are always elliptical, including circular orbits.

German: g-Beschleunigung