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LaRa (Lander Radioscience)
OperatorESA&Roscosmos
ManufacturerAntwerp Space N.V.[1]
Instrument typeRadio science/Transponder
FunctionMonitor the rotation and orientation of Mars
Mission durationPlanned: ≥ 1 Earth year[2]
Websitelara.oma.be
Properties
Massless than 2.2 kg[3]
DimensionsLength: 23 cm for the transponder (7-9 cm for the antennas)[3]
Power consumption≈ 40W[3]
Spectral bandX band(uplink: 7.174 GHz, downlink: 8.428 GHz)
Host spacecraft
SpacecraftKazachok
OperatorESA&Roscosmos
Launch dateAugust–October 2022[4]
RocketProton-M/Briz-M
Launch siteBaikonur

LaRa (Lander Radioscience)is a Belgian radio science experiment that will be placed onboardKazachok,planned to be launched in 2022.[2][4]LaRa will monitor theDoppler frequency shiftof a radio signal traveling between the Martian lander and theEarth.These Doppler measurements will be used to precisely observe the orientation and rotation ofMars,leading to a better knowledge of the internal structure of the planet.[5][6]

Instrument description[edit]

LaRa will obtain coherent two-way Doppler measurements from theX bandradio link betweenKazachokand large antennas on Earth, like those of theDeep space network.The relative radial velocity between the Earth and the Martian lander is inferred from Doppler shifts measured at the Earth ground stations.Masersat the Earth's ground stations ensure the frequency stability.[6]Véronique Dehant,scientist at theRoyal Observatory of Belgium,is thePrincipal Investigatorof the experiment.[2][7]

Antwerp Space N.V.,[1]a subsidiary ofOHB SE,is the manufacturer of the LaRa instrument.[2]The main parts of the transponder are the coherent detector, the transmitter with the Solid-State Power Amplifier, themicro controller unit,the receiver and thepower supply unit.TheAllan deviation(quantifying the frequency stability of the signal) of the measurements is expected to be lower thanat 60 second integration time.

The LaRa high-performance antennas were designed at theUniversité catholique de LouvaininBelgiumto obtain an optimalantenna gaincentered on an elevation (angle of the line-of-sight from the lander to Earth) of about 30° to 55°.[8]There will be three antennas: two for the transmission (for redundancy purposes) and one for reception.[9]Cables connect the transponder to the three antennas.

Belgium and theBelgian Federal Science Policy Office(BELSPO) fund the development and the manufacturing of LaRa throughESA's PRODEX program.[10]

Scientific objectives[edit]

LaRa will study the rotation of Mars as well as its internal structure, with particular focus on itscore.It will observe the Martianprecessionrate, thenutations,and thelength-of-day variations,as well as thepolar motion.The precession and the nutations are variations in the orientation of Mars's rotation axis in space, the precession being the very long term motion (about 170 000 years for Mars) while the nutations are the variations with a shorter period (annual, semi-annual, ter-annual,... periods). A precise measurement of the Martian nutations enables an independent determination of the size and density of the liquid core because of aresonancein the nutation amplitudes.[11]The resonant amplification of the low-frequency forced nutations depends sensibly on the size,moment of inertia,and flattening of thecore.This amplification is expected to correspond to a displacement of between a few to forty centimeters on Mars surface.[12]Observing the amplification allows to confirm the liquid state of the core and to determine some core properties.

LaRa will also measure variations in the rotationangular momentumdue to the redistribution of masses, such as the migration of ice from thepolar capsto the atmosphere and the sublimation/condensation cycle of atmospheric CO2.[13]

See also[edit]

References[edit]

  1. ^ab"LaRa".Antwerp Space.Archived fromthe originalon 11 May 2020.Retrieved13 March2020.
  2. ^abcd"Exomars 2020 surface platform".European Space Agency.Retrieved21 December2018.
  3. ^abc"LaRa instrument characteristics".Royal Observatory of Belgium.Retrieved21 December2018.
  4. ^ab"N° 6–2020: ExoMars to take off for the Red Planet in 2022"(Press release).ESA.12 March 2020.Retrieved12 March2020.
  5. ^Dehant, Veronique; Folkner, William; Renotte, Etienne; Orban, Daniel; Asmar, Sami; Balmino, Georges; Barriot, Jean-Pierre; Benoist, Jeremy; Biancale, Richard; Biele, Jens; Budnik, Frank; Burger, Stefaan; De Viron, Olivier; Häusler, Bernd; Karatekin, Özgur; Le Maistre, Sébastien; Lognonné, Philippe; Menvielle, Michel; Mitrovic, Michel; Pätzold, Martin; Rivoldini, Attilio; Rosenblatt, Pascal; Schubert, Gerald; Spohn, Tilman; Tortora, Paolo; Van Hoolst, Tim; Witasse, Olivier; Yseboodt, Marie (2009). "Lander radioscience for obtaining the rotation and orientation of Mars".Planetary and Space Science.57(8–9). Planetary and Space Science, Volume 57, Issues 8–9, July 2009, Pages 1050-1067.: 1050–1067.Bibcode:2009P&SS...57.1050D.doi:10.1016/j.pss.2008.08.009.
  6. ^ab"LaRa Homepage".Royal Observatory of Belgium.Retrieved21 December2018.
  7. ^"LaRa Team".Royal Observatory of Belgium.Retrieved21 December2018.
  8. ^"Space Antennas – Antennas Group".Université Catholique de Louvain. 15 May 2018.Retrieved21 December2018.
  9. ^LaRa (Lander Radioscience) on the ExoMars 2020 Surface Platform.(PDF) Véronique Dehant, Sébastien Le Maistre, Rose-Marie Baland, etal. EPSC Abstracts. Vol. 12, EPSC2018-31, 2018. European Planetary Science Congress 2018.
  10. ^"Belgium and LaRa on their way to Mars"(Press release).Royal Observatory of Belgium.14 May 2018.Retrieved21 December2018.
  11. ^Dehant, V.; Van Hoolst, T.; Defraigne, P. (January 2000). "Computation of Mars' transfer functions for nutations, tides and surface loading".Physics of the Earth and Planetary Interiors.117(1–4): 385–395.Bibcode:2000PEPI..117..385D.doi:10.1016/S0031-9201(99)00108-9.
  12. ^Yseboodt, M.; Dehant, V.; Péters, M.-J. (2017). "Signatures of the Martian rotation parameters in the Doppler and range observables".Planetary and Space Science.144:74–88.doi:10.1016/j.pss.2018.03.020.S2CID126262079.
  13. ^Karatekin, O.; de Viron, O.; Lambert, S.; Dehant, V.; Rosenblatt, P.; Van Hoolst, T.; Le Maistre, S. (August 2011). "Atmospheric angular momentum variations of Earth, Mars and Venus at seasonal time scales".Planetary and Space Science.59(10): 923–933.Bibcode:2011P&SS...59..923K.doi:10.1016/j.pss.2010.09.010.

External links[edit]

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