A mirror ball of half a ton in Earth's orbit

 The Lageos satellite is orbiting Earth

Two balls, to be exact. They fly in almost polar circular orbits at an altitude of about 6000 kilometers. The diameter of each ball is 60 centimeters, its mass is 400 kg! There are no voids or cavities inside. The balls are brass on the outside (coated with aluminum). Inside also filled with brass. On the outside there are 426 corner reflectors (they are coated with quartz). An area can be irradiated with a laser and its location is very precise.

 Assembly of the satellite

Meet LAGEOS-1, launched in 1976 by the Americans with the Delta 2000 rocket, and LAGEOS-2, an American-Italian satellite launched in 1992 by the Space Shuttle.

Determining the distance to the satellite using a laser rangefinder

LAGEOS stands for Laser Geodynamics Satellite or Laser Geometric Environmental Observation Survey. It is needed to study the Earth with a laser. By irradiating a satellite with a laser rangefinder, we can know the exact position of the satellite. And by irradiating the satellite from several points (and laser rangefinder stations on Earth several dozen), we can know the exact distance between stations.  For example, LAGEOS allows us to determine the movement of tectonic plates, and the plates move several millimeters, the fastest - centimeters per year.

In order to determine the exact distance of a satellite's orbit, it must be as stable as possible. For this purpose, it was launched so high (almost 6000 kilometers). Even at this altitude, there is a part of the atmosphere. In order for it to have a minimal impact, the satellite has a record mass-to-surface ratio - a weight of 400 kg with a diameter of 60 cm. There are no automatics or electronics on the satellite. Thanks to the measures taken and the spherical shape, LAGEOS will be in orbit for about 8.4 million years.

 A sign inside the satellite

Due to the fact that LAGEOS will be in orbit for about 8.4 million years, it was decided to seal it with a plaque for descendants, according to calculations it should remain in the atmosphere, but whether it can be found - who knows?

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