LaRa
| Operator | ESA & Roscosmos |
|---|---|
| Manufacturer | AntwerpSpace N.V..[1] |
| Instrument type | Radio science/Transponder |
| Function | Monitor the rotation and orientation of Mars |
| Mission duration | Planned: ≥ 1 Earth year[2] |
| Website | lara |
| Properties | |
| Mass | less than 2.2 kg[3] |
| Dimensions | Length: 23 cm for the transponder (7-9 cm for the antennas)[3] |
| Power consumption | about 40 W when switched on[3] |
| Spectral band | X band (uplink: 7.174 GHz, downlink: 8.428 GHz) |
| Host spacecraft | |
| Spacecraft | ExoMars 2020 surface platform |
| Operator | ESA & Roscosmos |
| Launch date | July 2020[4] |
LaRa (Lander Radioscience) is a Belgian radio science experiment that will be placed onboard ExoMars 2020 surface platform, planned to be launched in 2020[2][4]. LaRa will monitor the Doppler frequency shift of a radiosignal 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.[5][6]
Instrument description
LaRa will obtain coherent two-way Doppler measurements from the X-band radio link between the ExoMars 2020 Surface Platform 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.[6] Dr. Véronique Dehant, scientist at the Royal Observatory of Belgium, is the Principal Investigator of the instrument[2][7].
The LaRa high-performance antennas are 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 Lander to Earth) of about 30° to 55°[8]. There will be 3 antennas: 2 for the transmission (for redundancy purposes) and 1 for reception[9].
Belgium and the Belgian Science Policy (BELSPO) fund the development and the manufacturing of LaRa through the ESA PRODEX program[10].
Scientific objectives
LaRa will study the rotation of Mars as well as its internal structure, with particular focus on its core. It will observe the Martian precession rate, the nutations, and the length-of-day variations, as well as possibly the polar motion.
A precise measurement of the variations in the orientation of Mars’ spin axis in space enables an independent determination of the size of the core via a resonance in the nutation amplitudes. The resonant amplification of the low-frequency forced nutations depends sensibly on the size, moment of inertia, and flattening of the core. Observing it allows to determine core properties and to confirm the liquid state of the core.[11]
LaRa will also detect variations in the rotation angular momentum due to the redistribution of masses, such as the migration of ice from the polar caps to the atmosphere and the sublimation/condensation cycle of atmospheric CO.2[12]
References
- ^ https://www.antwerpspace.be/en/products/flight-products/lara
- ^ a b c "Exomars 2020 surface platform". European Space Agency. Retrieved 21 December 2018.
- ^ a b c "LaRa instrument characteristics". Royal Observatory of Belgium. Retrieved 21 December 2018.
- ^ a b "N° 11–2016: Second ExoMars mission moves to next launch opportunity in 2020" (Press release). ESA. 2 May 2016. Retrieved 21 December 2018.
- ^ "Dehant et al.,Lander radioscience for obtaining the rotation and orientation of Mars, 'Planetary and Space Science, Volume 57, Issues 8–9, July 2009, Pages 1050-1067". Retrieved 21 December 2018.
- ^ a b "LaRa Homepage". Royal Observatory of Belgium. Retrieved 21 December 2018.
- ^ "LaRa Team". Royal Observatory of Belgium. Retrieved 21 December 2018.
- ^ "Space Antennas – Antennas Group". Université Catholique de Louvain. Retrieved 21 December 2018.
- ^ LaRa (Lander Radioscience) on the ExoMars 2020 Surface Platform. (PDF) Véronique Dehant, Sébastien Le Maistre, Rose-Marie Baland, et al. EPSC Abstracts. Vol. 12, EPSC2018-31, 2018. European Planetary Science Congress 2018.
- ^ "Belgium and LaRa on their way to Mars" (Press release). Royal Observatory of Belgium. 14 May 2018. Retrieved 21 December 2018.
- ^ 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. doi:10.1016/S0031-9201(99)00108-9.
- ^ 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. doi:10.1016/j.pss.2010.09.010.
External links
- Home site of LaRa at the Royal Observatory of Belgium.
- Dehant et al., Lander radioscience for obtaining the rotation and orientation of Mars, ‘’Planetary and Space Science’’, Volume 57, Issues 8–9, July 2009, Pages 1050-1067. doi:10.1016/j.pss.2008.08.009.