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The article “NOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance”, discusses a spectrometer suite incorporated into the ExoMars Trace Gas Orbiter, NOMAD (“Nadir and Occultation for Martian Discovery”). The article mentions that the purpose of NOMAD is to study the trace gases, clouds and dust present within Mars’ atmosphere.
The main purpose of the Trace Gas Orbiter (TGO) is to detect and quantify trace gases on Mars, a process that is only possible with NOMAD since it was specifically designed to detect and quantify these gases.
The NOMAD satellite is equipped with three spectrometers which allows it to measure the spectral emissions from the atmosphere, spanning ultraviolet, visible light, and infrared wavelengths.
According to the article “NOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance”, the device will “conduct a spectroscopic survey of Mars’ atmosphere” using its three spectrometers. The Solar Occultation spectrometer (SO) has a range of 2.3-4.3um which operates in the infrared range. The Limb Nadir and Solar Occultation spectrometer has a range of 2.3-3.8um which also operates in the infrared range. The Ultraviolet/visible spectrometer has a range of 200-650nm which operates in the ultraviolet and visible light range. The spectrometers working within these ranges allow NOMAD to quantify and measure the trace gases.
Water vapour is also an important trace gas to map as it provides vital information in cloud formation. Previously, water vapour detection has been very scarce but NOMAD is fully equipped to monitor the water vapour levels.
The article “Water heavily fractionated as it ascends on Mars as revealed by ExoMars/NOMAD” stated the NOMAD is capable of producing “vertical profiles and global maps of water” using the spectrometers onboard. It uses the data obtained by the SO to create a map of water vapour concentrations in the atmosphere.
Methane, a key biomarker, is one of the gases that is commonly searched for in Mars’ by every orbiter/rover but the TGO’s NOMAD showed that methane is absent from the atmosphere. NOMAD is a highly sensitive instrument, even more so than other instruments available, but as it didn’t detect any amount of methane this has created a cloud of confusion when comparing the data obtained by the TGO and data obtained by other rovers like Curiosity rover.
In conclusion, the NOMAD is a highly sensitive instrument that is very advanced than its counterparts and is capable of detecting very small amounts of gases available on Mars’ and mapping it.
References
Vandaele, A. C., Lopez-Moreno, J.-J., Patel, M. R., Bellucci, G., Daerden, F., Ristic, B., Robert, S., Thomas, I. R., Wilquet, V., Allen, M., Alonso-Rodrigo, G., Altieri, F., Aoki, S., Bolsée, D., Clancy, T., Cloutis, E., Depiesse, C., Drummond, R., Fedorova, A., … Wolff, M. (2018). Nomad, an integrated suite of three spectrometers for the ExoMars Trace Gas Mission: Technical Description, science objectives and expected performance. Space Science Reviews, 214(5). https://doi.org/10.1007/s11214-018-0517-2
Villanueva, G. L., Liuzzi, G., Crismani, M. M., Aoki, S., Vandaele, A. C., Daerden, F., Smith, M. D., Mumma, M. J., Knutsen, E. W., Neary, L., Viscardy, S., Thomas, I. R., Lopez-Valverde, M. A., Ristic, B., Patel, M. R., Holmes, J. A., Bellucci, G., & Lopez-Moreno, J. J. (2021). Water heavily fractionated as it ascends on Mars as revealed by ExoMars/Nomad. Science Advances, 7(7). https://doi.org/10.1126/sciadv.abc8843
Has Mars' methane gone missing?: Space. EarthSky. (2019, January 3). Retrieved October 7, 2021, from https://earthsky.org/space/esa-exomars-trace-gas-orbiter-missing-methane/.
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