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{{Infobox spacecraft instrument
| Name =  LaRa (Lander Radioscience)
| Image =
| Caption =

| Operator = [[European Space Agency|ESA]] & [[Roscosmos]]
| Manufacturer = Antwerp Space N.V.<ref name="antwerpspace">{{cite web |url=https://www.antwerpspace.be/en/products/flight-products/lara |title=LaRa |work=Antwerp Space |access-date=13 March 2020 |archive-date=11 May 2020 |archive-url=https://web.archive.org/web/20200511173107/https://www.antwerpspace.be/en/products/flight-products/lara |url-status=dead }}</ref>
| Type = [[Outline of radio science|Radio science]]/[[Transponder]]
| Function = Monitor the rotation and orientation of Mars
| Mission_Duration =  Planned: ≥ 1 Earth year<ref name="exomars2020sp">{{cite web |url=http://exploration.esa.int/mars/56933-exomars-2020-surface-platform/ |title=Exomars 2020 surface platform |publisher=European Space Agency |access-date=21 December 2018}}</ref>
| Began = <!--date operations began (single instruments only)-->
| Ceased = <!--date operations ceased (single instruments only)-->
| Webpage = {{url|https://lara.oma.be/}}

| Mass = less than 2.2 kg<ref name="LaRa instrument">{{cite web |url=https://lara.oma.be/instrument |title=LaRa instrument characteristics |publisher= [[Royal Observatory of Belgium]] |access-date=21 December 2018}}</ref>
| Dimensions = Length: 23 cm for the transponder (7-9 cm for the antennas)<ref name="LaRa instrument"/> 
| Power_consumption = ≈ 40 [[Watt|W]]<ref name="LaRa instrument"/>
| Spectral_Band = [[X band]] (uplink: 7.174 GHz, downlink: 8.428 GHz)
| Data_Rate =

| Spacecraft = [[Kazachok]] 
| SC_Operator = [[European Space Agency|ESA]] & [[Roscosmos]]
| Launch = August–October 2022<ref name="LaunchMoved2022">{{cite press release |url=http://www.esa.int/Newsroom/Press_Releases/ExoMars_to_take_off_for_the_Red_Planet_in_2022 |title=N° 6–2020: ExoMars to take off for the Red Planet in 2022 |publisher=[[ESA]] |date=12 March 2020 |access-date=12 March 2020}}</ref>
| Rocket = [[Proton-M]]/[[Briz-M]]
| Launch_Site = [[Baikonur Cosmodrome|Baikonur]]
| landing_date = April–June 2023
| landing_site = [[Oxia Planum]]
| COSPAR = <!--COSPAR ID of host spacecraft-->
}}

'''LaRa (Lander Radioscience)''' is a Belgian radio science experiment that will be placed onboard [[Kazachok]], planned to be launched in 2022.<ref name="exomars2020sp"/><ref name="LaunchMoved2022"/> LaRa will monitor the [[Doppler effect|Doppler frequency shift]] of a radio signal traveling between the Martian lander and the [[Earth]]. These Doppler measurements will be used to precisely observe the orientation and rotation of [[Mars]], leading to a better knowledge of the internal structure of the planet.<ref name="Dehant et al. (2009)">{{cite journal |doi=10.1016/j.pss.2008.08.009|title= Lander radioscience for obtaining the rotation and orientation of Mars. |year= 2009 |publisher=Planetary and Space Science, Volume 57, Issues 8–9, July 2009, Pages 1050-1067.|last1= Dehant |first1= Veronique |last2= Folkner |first2= William |last3= Renotte |first3= Etienne |last4= Orban |first4= Daniel |last5= Asmar |first5= Sami |last6= Balmino |first6= Georges |last7= Barriot |first7= Jean-Pierre |last8= Benoist |first8= Jeremy |last9= Biancale |first9= Richard |last10= Biele |first10= Jens |last11= Budnik |first11= Frank |last12= Burger |first12= Stefaan |last13= De Viron |first13= Olivier |last14= Häusler |first14= Bernd |last15= Karatekin |first15= Özgur |last16= Le Maistre |first16= Sébastien |last17= Lognonné |first17= Philippe |last18= Menvielle |first18= Michel |last19= Mitrovic |first19= Michel |last20= Pätzold |first20= Martin |last21= Rivoldini |first21= Attilio |last22= Rosenblatt |first22= Pascal |last23= Schubert |first23= Gerald |last24= Spohn |first24= Tilman |last25= Tortora |first25= Paolo |last26= Van Hoolst |first26= Tim |last27= Witasse |first27= Olivier |last28= Yseboodt |first28= Marie |journal= Planetary and Space Science |volume= 57 |issue= 8–9 |pages= 1050–1067 |bibcode= 2009P&SS...57.1050D }}</ref><ref name="LaRa Home">{{cite web |url=https://lara.oma.be |title=LaRa Homepage |publisher= [[Royal Observatory of Belgium]] |access-date=21 December 2018}}</ref>

==  Instrument description ==
LaRa will obtain coherent two-way Doppler measurements from the [[X band]] radio link between [[Kazachok]] and large antennas on Earth, like those of the [[Deep space network]]. The relative radial velocity between the Earth and the Martian lander is inferred from Doppler shifts measured at the Earth ground stations. [[Masers]] at the Earth's ground stations ensure the frequency stability.<ref name="LaRa Home" /> [[Véronique Dehant]], scientist at the [[Royal Observatory of Belgium]], is the [[Principal Investigator]] of the experiment.<ref name="exomars2020sp"/><ref name="Team LaRa">{{cite web |url=https://lara.oma.be/team |title=LaRa Team |publisher= [[Royal Observatory of Belgium]] |access-date=21 December 2018}}</ref>

Antwerp Space N.V.,<ref name="antwerpspace" /> a subsidiary of [[OHB SE]], is the manufacturer of the LaRa instrument.<ref name="exomars2020sp" /> The main parts of the transponder are the coherent detector, the transmitter with the Solid-State Power Amplifier, the [[Microcontroller|micro controller unit]], the receiver and the [[Power Supply Unit|power supply unit]]. The [[Allan variance|Allan deviation]] (quantifying the frequency stability of the signal) of the measurements is expected to be lower than <math>10^{-13}</math>at 60 second integration time.

The LaRa high-performance antennas were designed at the [[Université catholique de Louvain]] in [[Belgium]] to obtain an optimal [[antenna gain]] centered on an elevation (angle of the line-of-sight from the lander to Earth) of about 30° to 55°.<ref name="larauclouvain">{{cite web |url=https://sites.uclouvain.be/AntennaGroup/research/space-antennas/ |title=Space Antennas – Antennas Group |date=15 May 2018 |publisher=Université Catholique de Louvain |access-date=21 December 2018}}</ref> There will be three antennas: two for the transmission (for redundancy purposes) and one for reception.<ref name="Dehant et al. 2018">[https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-31.pdf 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.</ref> Cables connect the transponder to the three antennas.

Belgium and the [[Belgian Federal Science Policy Office]] (BELSPO) fund the development and the manufacturing of LaRa through [[ESA]]'s PRODEX program.<ref name="larapr2018">{{cite press release |url=https://www.astro.oma.be/en/belgium-and-lara-on-their-way-to-mars/ |title=Belgium and LaRa on their way to Mars |publisher=[[Royal Observatory of Belgium]] |date=14 May 2018 |access-date=21 December 2018}}</ref>

== Scientific objectives ==  
LaRa will study the rotation of Mars as well as its internal structure, with particular focus on its [[Planetary core|core]]. It will observe the Martian [[precession]] rate, the [[nutation]]s, and the [[Day length fluctuations|length-of-day variations]], as well as the [[polar 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 a [[resonance]] in the nutation amplitudes.<ref name="Dehant00">{{cite journal|last1=Dehant|first1=V.|last2=Van Hoolst|first2=T.|last3=Defraigne|first3=P.|date=January 2000|title=Computation of Mars' transfer functions for nutations, tides and surface loading|journal=Physics of the Earth and Planetary Interiors|volume=117|issue=1–4|pages=385–395|doi=10.1016/S0031-9201(99)00108-9|bibcode=2000PEPI..117..385D }}</ref> The resonant amplification of the low-frequency forced nutations depends sensibly on the size, [[moment of inertia]], and flattening of the [[Planetary core|core]]. This amplification is expected to correspond to a displacement of between a few to forty centimeters on Mars surface.<ref>{{Cite journal|last1=Yseboodt|first1=M.|last2=Dehant|first2=V.|last3=Péters|first3=M.-J.|date=2017|title=Signatures of the Martian rotation parameters in the Doppler and range observables|journal=Planetary and Space Science|volume=144|pages=74–88|doi=10.1016/j.pss.2018.03.020|s2cid=126262079 |doi-access=}}</ref> 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 rotation [[angular momentum]] due to the redistribution of masses, such as the migration of ice from the [[Martian polar ice caps|polar caps]] to the atmosphere and the sublimation/condensation cycle of atmospheric CO<sub>2</sub>.<ref name="Karatekin et al. 2011">{{cite journal |last1=Karatekin |first1=O. |last2=de Viron |first2=O. |last3=Lambert |first3=S. |last4=Dehant |first4=V. |last5=Rosenblatt |first5=P. |last6=Van Hoolst |first6=T. |last7=Le Maistre |first7=S. |title=Atmospheric angular momentum variations of Earth, Mars and Venus at seasonal time scales |journal=Planetary and Space Science |date=August 2011 |volume=59 |issue=10 |pages=923–933 |doi=10.1016/j.pss.2010.09.010 |bibcode=2011P&SS...59..923K }}</ref>

==See also==
*[[Rotation and Interior Structure Experiment]], a similar radio science experiment by the InSight Mars lander

== References ==
{{reflist}}

{{Exomars}}
{{Mars}}
{{Geography of Mars}}
{{Satellite and spacecraft instruments}}
{{Portal bar|Astronomy|Chemistry|Geology|Solar System|Science}}

==External links==
*Home site of [https://lara.oma.be/ LaRa] at the Royal Observatory of Belgium. 
*[https://twitter.com/LaraExoMars Twitter account of LaRa].

[[Category:ExoMars]]
[[Category:Geology of Mars]]
[[Category:Spacecraft instruments]]