TIGO carries out first laser ranging of new European satellites

The Transportable Integrated Geodetic Observatory (TIGO) of the University of Concepción (UdeC) and the Federal Agency for Cartography and Geodesy (BKG), carried out the first international laser ranging of the new Galileo satellites developed by the European Union.

The contact with the satellites, located at an altitude of 23 thousand 230 kilometers, allowed for a highly precise laser measurement of their distance from Earth, with less than a centimeter margin of error.  The first laser ranging of the first IOV Galileo satellite, was completed November 26 at 23:45 p.m. Chilean time, and the next for the second IOV Galileo satellite occurred three days later, on November 29 at 7:05 a.m.

The initial laser ranging was achieved using a beam of light from an infrrared laser at 847 nanometers.  The operation, according to the responsible parties, proceeded like a video game on a planetary scale, working from orbital  predictions given by the European Space Operations Center (ESOC) of the European Space Agency (ESA) in Darmstadt, Germany and the TIGO team, headed by Michael Häffner.  In practice, you aim and shoot a laser beam -having first calibrated the laser system to the prototype satellite of the European Navigation system, GIOVE-A.

The laser rangings were carried out by the Chilean TIGO team,  composed of Marcos Avendaño, Alejandro Fernández, César Guaitiao, and Víctor Mora.  After searching for 4 hours, Avendaño and Mora were the first to recognize the signals of laser light reflected by these two satellites.  Uncertainty in satellite location was reduced from kilometers to less than one centimeter thanks to the first measurements.

As in many modern satellites, the Galileo satellites are equipped with retroreflectors that work like cat eyes, sending the laser beam back to its origin.  The time taken for laser light to return to Earth is measured with an ultra-precise clock.  Light velocity is fixed, so the distance to the satellite can be measured to within less than a centimeter precision.

TIGO from Concepción was the first station among the forty that make up the International Laser Ranging Service (IRLS) to measure the satellites Galileo.  Moreover, as the satellites progressed, Herstmonceaux in the United Kingdom and Matera in Italy also were successful.

Laser ranging is widely used to accurately determine satellite orbits, and this is esssential information when calibrating instruments onboard satellites, to contribute to the International Terrestrial Reference Frame (Standardized Global System of Geodesic Coordinates) which measures subtle local movements stemming from the dynamics of plate tectonics, and that also continuously measures the distance between the Earth and the Moon, thanks to retroreflectors that were installed on the surface of the Moon by American and Russian missions.



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