LARES

Spacecraft nº:

Italian spacecraft nº: 28

Launch data: Designation  38077 / 12006A Launch date  13 Feb 2012 - 10:00 UT Launch site  Ko, ELV (old ELA-1 pad) Launch vehicle  Vega (#VV01) Mission  Geodesy Earth orbit on Feb 14.61: Perigee / Apogee  1435 x 1452 km Eccentricity  0.001 Inclination  69.49 deg Period  114.73 min

Spacecraft data: Prime manufacturer  Carlo Gavazzi Space SpA Platform   Operator  ASI (Italy) Mass at launch  about 400 kg Dry Mass   kg Basic shape  sphere Dimension (m)  dia: 37.6 cm Equipment  92 cube corner reflectors Solar array   Stabilization   Propulsion  none DC power  none Design lifetime  no more active on July 2012

Photo of Lares, ALMASat-1 and the seven CubeSats before encapsulation in fairing. Credit: ESA

LARES, ALMASAT and Cubesats being prepared for launch. Credit: ESA

Credit: ESA

LARES ready for launch. Credit: ESA/S. Corvaja

Description:

• LARES (Laser Relativity Satellite) is the latest in a series of passive satellite with laser mirrors for the study of the Earth gravitational field and general relativity measurements (Lense-Thirring effect).
• LARES is basically a solid sphere made of Tungsten with a diameter of 376 mm and a mass of 400 kg. The surface of the sphere is covered by 92 laser retroreflectors (Corner Cube Reflectors - CCR), and will be used as a test particle to probe relativistic effects in the Earth's gravitational field. To achieve its scientific objectives, LARES will be injected into a circular orbit at 1200 km altitude with an inclination of 71°.
• LARES is claimed to have the lowest ballistic coefficient of any satellite launched to date (this means its orbit will be very stable); an estimating of the BC is around 0.0011 m**2/kg.
• Researchers will use data from the LARES mission to investigate the Lense-Thirring effect, which is predicted by Albert Einstein's theory of general relativity. Previous missions have measured the effect with a precision of 10 percent, but LARES will improve scientists' understanding by a factor of ten.
• The name of the attached payload on the Vega AVUM stage is the LARES A&H/SS (Avionics and Harness Subsystem) and consists of several boxes on one `petal' (sector) of the LARES support system. The system is built by Temis S.r.l. of Milano, while the overall support system is built by the Milan company OHB CGS (formerly Carlo Gavazzi Space). Overall mass of the LARES support system is probably 300 kg, and the dry AVUM is around 660 kg for a total in orbit mass for the object of about 960 kg.
• The main scientific objectives of the LARES mission are:
  • High precision tests of Einstein's theory of general relativity, in particular:
    • A measurement of the Lense-Thirring effect due to the Earth's angular momentum and a high precision test of the Earth's gravitomagnetic field. The Lense-Thirring effect is a tiny shift of the orbit of a test particle. Gravitomagnetic field and Lense-Thirring effect are theoretical predictions of Einstein's theory of general relativity.
    • An improved, high precision, test of the inverse square law for very weak-field gravity and test of the equivalence principle.
    • A measurement of the general relativistic perigee precession of LARES and a high precision measurement of the corresponding combination of the PPN (Parametrized-Post-Newtonian) parameters beta and gamma. The PPN parameters beta and gamma test Einstein's theory of gravitation versus other metric theories of gravitation.
    • Other tests of general relativity and gravitation.
  • Measurements and improved determinations in geodesy and geodynamics.

Mission details:

• Delayed from 2010, mid-2011 and October 2011.
• Delayed again from Jan 26 and Feb 9, 2012.
• ESA's new small satellite launch vehicle, Vega, made its first flight successfully on Feb 13, 2011.
  The Vega booster took off from the Ensemble de Lancement Vega (ELV) at Kourou and headed northeast. The Zefiro 9A third stage burnt out at 1005 UTC and entered a marginal orbit (one estimate is around -30 x 775 km; another solution from the limited data available is around 50-60 km x 250-500 km). The stage probably reentered at first perigee at around 1112 UTC south of New Zealand, and has not been cataloged. The AVUM stage first burn was completed at 1008 UTC and probably reached an orbit of around 180 x 1450 km. At 1048 UTC the AVUM second burn began and resulted in a 1435 x 1452 km x 69.5 deg orbit.
• The LARES 'Laser Relativity Satellite' is the primary payload and was released into this orbit at 1055 UTC.
  At 1106-1110 UTC AVUM's third burn lowered the perigee resulting in an orbit of around 310 x 1441 km. At 1110 UTC the three P-PODs released their cargo. Finally at 1111 UTC AlmaSat was ejected, and the AVUM vented its remaining propellant, ending up in a 272 x 1431 km x 69.5 km orbit.