LARES (Laser Relativity Satellite) is a passive satellite system of the Italian Space Agency.[4]
LARES 1 was launched into orbit on 13 February 2012 at 10:00:00 UTC. It was launched on the first Vega rocket from the ESA Centre Spatial Guyanais in Kourou, French Guiana.[5]
The satellite is made of THA-18N, a tungsten alloy,[6] and houses 92 cube-corner retroreflectors, which are used to track the satellite via laser from stations on Earth. LARES's body has a diameter of about 36.4 centimetres (14.3 in) and a mass of about 387 kilograms (853 lb).[1][7] LARES was inserted in a nearly circular orbit near 1,451 kilometres (902 mi) and an inclination of 69.49 degrees. The satellite is tracked by the International Laser Ranging Service stations.[8]
The LARES satellite is the densest object known orbiting the Earth.[1] The high density helps reduce disturbances from environmental factors such as solar radiation pressure.[citation needed]
The main scientific target of the LARES mission is the measurement of the Lense–Thirring effect with an accuracy of about 1%, according to principal investigator Ignazio Ciufolini and the LARES scientific team,[9] but the reliability of that estimate is contested.[10]
In contrast, a recent analysis of 3.5 years of laser-ranging data reported a claimed accuracy of about 4%.[11] Critical remarks appeared later in the literature.[12][clarification needed]
Beyond the project's key mission, the LARES satellite may be used for other tests of general relativity as well as measurements in the fields of geodynamics and satellite geodesy.[13]
A second satellite, LARES 2, was launched into orbit on 13 July 2022 at 13:13:43 UTC on a Vega-C.[14] It was originally due to launch in mid-2021.[15][16] The launch was delayed to mid-2022 due to continuing impacts from the COVID-19 pandemic.[17][18]
LARES 2 may improve the accuracy of the frame-dragging effect measurement to 0.2%.[19] Concerns about the actual possibility of reaching this goal were raised.[20] LARES 2 is made of a nickel alloy instead of a tungsten alloy.[21]
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