LARES (satellite)

The Laser Relativity Satellite ( LARES ) is a passive satellite of the Italian Space Agency ASI for the detection of the Lense- Thirring effect, a gravitomagnetic effect, which results from the general theory of relativity.

Operation

The Lense- Thirring effect, a condition caused by gravitomagnetism effect, which causes a rotating mass (the earth here ) the space-time around them and they go along this " twisted ". This has implications for the satellite orbit, which can be detected from the calculated by methods of classical physics position by accurate measurement of the deviation of the actual position of the satellite. Since this effect is very small, on the one hand a very precise measurement is necessary, on the other hand interference from other sources such as air friction, or interference with the Earth's magnetic field must be kept low, which is achieved by the choice of the orbit as well as the materials used. The position of the spacecraft is from ground stations by means of laser distance measurement with an accuracy of less than one centimeter. By combining the LARES measurements with measurements on the similarly constructed satellite LAGEOS 1 and 2 and started by the GRACE satellite models of the Earth's gravity is expected that the Lense- Thirring effect can be measured with a measuring error of 1%.

Construction

The completely passive spherical satellite consists of a tungsten alloy ( THA - 18N ) with a density of about 18,000 kg / m and reaches a diameter of only 36.4 cm, a mass of 387 kg. The satellite body is made of a single piece. The surface of the sphere is filled with 92 laser reflectors for tracking. All other parts such as screws and brackets for the laser reflectors are made of the same alloy as that of the satellite body.

With a density of about 15,325 kg / m³ LARES is regarded as the object with the largest average density, which draws its orbits in the solar system.

Since LARES has no conventional payload adapter due to its spherical shape, the upper stage of the rocket was fitted with special equipment that secures the satellite at startup and can release after reaching the target orbit. This A & H / SS ( Avionic & Harness / Support System) called device consists of a bearing shell for the satellites, four mechanical brackets that fix the satellite and later free and associated control electronics.

Mission

LARES was launched as the main payload on the maiden flight of the Vega rocket along with eight secondary payloads from the spaceport Guiana Space Centre in Kourou, French Guiana on 13 February 2012. The rocket put LARES 55 minutes after the start in a circular orbit of 1450 km altitude from.

Measurements for the primary mission will be carried out until 2016, but the satellite is due to its stable orbit with a lifetime of more than 20,000 years and its passive construction virtually unlimited for later measurements.

LARES can be used in addition to its main task for measurements in the area of ​​geodynamics and satellite geodesy.