This paper presents a review on the PECASUS service, which provides advisories on enhanced space weather activity for civil aviation. The advisories are tailored according to the Standards and ...Recommended Practices of the International Civil Aviation Organization (ICAO). Advisories are disseminated in three impact areas: radiation levels at flight altitudes, GNSS-based navigation and positioning, and HF communication. The review, which is based on the experiences of the authors from two years of running pilot ICAO services, describes empirical models behind PECASUS products and lists ground- and space-based sensors, providing inputs for the models and 24/7 manual monitoring activities. As a concrete example of PECASUS performance, its products for a post-storm ionospheric F2-layer depression event are analyzed in more detail. As PECASUS models are particularly tailored to describe F2-layer thinning, they reproduce observations more accurately than the International Reference Ionosphere model (IRI(STORM)), but, on the other hand, it is recognized that the service performance is much affected by the coverage of its input data. Therefore, more efforts will be directed toward systematic measuring of the availability, timeliness and quality of the data provision in the next steps of the service development.
•We measure water vapor abundances and aerosol properties at Gale Crater, Mars.•Precipitable water column is measured with a precision of ±0.6 μm.•Measured quantities include dust & ice fractions, ...particle sizes, and scale heights.•Results suggest substantial diurnal interactions of water vapor with the surface.•A large interannual change in water ice cloud/haze opacity is observed.
We derive water vapor column abundances and aerosol properties from Mars Science Laboratory (MSL) ChemCam passive mode observations of scattered sky light. This paper covers the methodology and initial results for water vapor and also provides preliminary results for aerosols. The data set presented here includes the results of 113 observations spanning from Mars Year 31 Ls = 291° (March 30, 2013) to Mars Year 33 Ls = 127° (March 24, 2016).
Each ChemCam passive sky observation acquires spectra at two different elevation angles. We fit these spectra with a discrete-ordinates multiple scattering radiative transfer model, using the correlated-k approximation for gas absorption bands. The retrieval proceeds by first fitting the continuum of the ratio of the two elevation angles to solve for aerosol properties, and then fitting the continuum-removed ratio to solve for gas abundances. The final step of the retrieval makes use of the observed CO2 absorptions and the known CO2 abundance to correct the retrieved water vapor abundance for the effects of the vertical distribution of scattering aerosols and to derive an aerosol scale height parameter.
Our water vapor results give water vapor column abundance with a precision of ±0.6 precipitable microns and systematic errors no larger than ±0.3 precipitable microns, assuming uniform vertical mixing. The ChemCam-retrieved water abundances show, with only a few exceptions, the same seasonal behavior and the same timing of seasonal minima and maxima as the TES, CRISM, and REMS-H data sets that we compare them to. However ChemCam-retrieved water abundances are generally lower than zonal and regional scale from-orbit water vapor data, while at the same time being significantly larger than pre-dawn REMS-H abundances. Pending further analysis of REMS-H volume mixing ratio uncertainties, the differences between ChemCam and REMS-H pre-dawn mixing ratios appear to be much too large to be explained by large scale circulations and thus they tend to support the hypothesis of substantial diurnal interactions of water vapor with the surface. Our preliminary aerosol results, meanwhile, show the expected seasonal pattern in dust particle size but also indicate a surprising interannual increase in water–ice cloud opacities.
The entry, descent and landing of Schiaparelli, the
ExoMars
Entry, descent and landing Demonstrator Module (EDM), offered a rare (once-per-mission) opportunity for
in situ
investigations of the ...martian environment over a wide altitude range. The aim of the
ExoMars
AMELIA experiment was to exploit the Entry, Descent and Landing System (EDLS) engineering measurements for scientific investigations of Mars’ atmosphere and surface. Here we present the simulations, modelling and the planned investigations prior to the Entry, Descent and Landing (EDL) event that took place on 19th October 2016. Despite the unfortunate conclusion of the Schiaparelli mission, flight data recorded during the entry and the descent until the loss of signal, have been recovered. These flight data, although limited and affected by transmission interruptions and malfunctions, are essential for investigating the anomaly and validating the EDL operation, but can also contribute towards the partial achievement of AMELIA science objectives.
The Mars2020 Perseverance Rover landed successfully on the Martian surface on the Jezero Crater floor (18.44°N, 77.45°E) at Martian solar longitude, Ls, ∼5° in February 2021. Since then, it has ...produced highly valuable environmental measurements with a versatile scientific payload including the MEDA (Mars Environmental Dynamics Analyzer) suite of environmental sensors. One of the MEDA systems is the PS pressure sensor system, which weighs 40 g and has an estimated absolute accuracy of better than 3.5 Pa and a resolution of 0.13 Pa. We present initial results from the first 414 sols of Martian atmospheric surface pressure observations by the PS, whose performance was found to meet its specifications. Observed sol‐averaged atmospheric pressures follow an anticipated pattern of pressure variation in the course of the advancing season and are consistent with data from other landing missions. The observed daily pressure amplitude varies by ∼2%–5 % of the sol‐averaged pressure, with absolute amplitude 10–35 Pa in an approximately direct relationship with airborne dust. During a regional dust storm, which began at Ls ∼ 135°, the daily pressure amplitude roughly doubled. The daily pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular, analysis of the daily pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations with data from other landers reveals the global scale seasonal behavior of Mars' atmosphere.
Plain Language Summary
Mars2020 Perseverance Rover successfully arrived on Mars in February 2021. It landed in an early Martian spring afternoon in a crater north of Mars' equator called Jezero crater. The rover is equipped with meteorological instruments that have so far produced extensive and valuable data for understanding the Martian atmosphere. One of the meteorological instruments is an accurate and precise pressure sensor. The pressure sensor has revealed large changes in the pressure over the seasons that are related to large changes in the actual mass of the Martian atmosphere. This is in line with seasonal pressure changes measured during previous Mars missions and can be explained as the condensation of the atmosphere onto the Martian poles and its subsequent sublimation. On a shorter time scale, the pressure sensor revealed complex pressure changes over a Martian day. These variations are thought to be related to atmospheric dust, whose ubiquitous nature is known to have a strong influence on the Martian climate. As the seasons progressed, the daily pressure variations morphed to exhibit different patterns likely related to the large‐scale regional changes in the atmosphere. Comparison of Perseverance pressure observations with other landers revealed the global nature of the atmosphere.
Key Points
The atmospheric pressure observations by Perseverance Rover have proved to be of excellent quality fulfilling expectations
Jezero crater pressure exhibits significant differences to other Martian areas likely due to varying regional geography and solar forcing
Overall, the diurnal and seasonal atmospheric pressure cycles at Jezero Crater follow an anticipated pattern of pressure variation
In situ surface pressures measured at 2 s intervals during the 150 sol Phoenix mission are presented and seasonal variations discussed. The lightweight Barocap®/Thermocap® pressure sensor system ...performed moderately well. However, the original data processing routine had problems because the thermal environment of the sensor was subject to more rapid variations than had been expected. Hence, the data processing routine was updated after Phoenix landed. Further evaluation and the development of a correction are needed since the temperature dependences of the Barocap sensor heads have drifted after the calibration of the sensor. The inaccuracy caused by this appears when the temperature of the unit rises above 0°C. This frequently affects data in the afternoons and precludes a full study of diurnal pressure variations at this time. Short‐term fluctuations, on time scales of order 20 s are unaffected and are reported in a separate paper in this issue. Seasonal variations are not significantly affected by this problem and show general agreement with previous measurements from Mars. During the 151 sol mission the surface pressure dropped from around 860 Pa to a minimum (daily average) of 724 Pa on sol 140 (Ls 143). This local minimum occurred several sols earlier than expected based on GCM studies and Viking data. Since battery power was lost on sol 151 we are not sure if the timing of the minimum that we saw could have been advanced by a low‐pressure meteorological event. On sol 95 (Ls 122), we also saw a relatively low‐pressure feature. This was accompanied by a large number of vertical vortex events, characterized by short, localized (in time), low‐pressure perturbations.
The Finnish Meteorological Institute (FMI) provides a relative humidity measurement sensor (HS) for NASA's Mars 2020 rover. The sensor is a part of the Mars Environmental Dynamic Analyzer (MEDA), a ...suite of environmental sensors provided by Spain's Centro de Astrobiología. The main scientific goal of the humidity sensor is to measure the relative humidity of the Martian atmosphere near the surface and to complement previous Mars mission atmospheric measurements for a better understanding of Martian atmospheric conditions and the hydrological cycle. Relative humidity has been measured from the surface of Mars previously by Phoenix and Curiosity. Compared to the relative humidity sensor on board Curiosity, the MEDA HS is based on a new version of the polymeric capacitive humidity sensor heads developed by Vaisala. Calibration of humidity devices for Mars conditions is challenging and new methods have been developed for MEDA HS. Calibration and test campaigns have been performed at the FMI, at University of Michigan and the German Aerospace Center (DLR) in Berlin to achieve the best possible calibration. The accuracy of HS and uncertainty of the calibration has been also analysed in detail with VTT Technical Research Centre of Finland. Assessment of sensor performance after landing on Mars confirms that the calibration has been successful, and the HS is delivering high quality data for the science community.
•MEDA HS humidity sensor onboard NASA's Perseverance rover provides relative humidity measurements from the surface of Mars.•MEDA HS provides regular measurements of Martian near-surface relative humidity and water vapor volume mixing ratio (VMR).•The calibration uncertainty of MEDA HS has been analysed and it confirms that sensor provides high accuracy humidity data.•MEDA HS data can be used to understand the Martian hydrological cycle.
Acoustics has become extraterrestrial and Mars provides a new natural laboratory for testing sound propagation models compared to those ones on Earth. Owing to the unique combination of a microphone ...and two sound sources, the Ingenuity helicopter and the SuperCam laser-induced sparks, the Mars 2020 Perseverance rover payload enables the in situ characterization of unique sound propagation properties of the low-pressure CO2-dominated Mars atmosphere. In this study, we show that atmospheric turbulence is responsible for a large variability in the sound amplitudes from laser-induced sparks. This variability follows the diurnal pattern of turbulence. In addition, acoustic measurements acquired over one Martian year reveal a variation of the sound intensity by a factor of 1.8 from a constant source due to the seasonal cycle of pressure and temperature that significantly modifies the acoustic impedance and shock-wave formation. Finally, we show that the evolution of the Ingenuity tones and laser spark amplitudes with distance is consistent with one of the existing sound absorption models, which is a key parameter for numerical simulations applied to geophysical experiments on CO2-rich atmospheres. Overall, these results demonstrate the potential of sound propagation to interrogate the Mars environment and will therefore help in the design of future acoustic-based experiments for Mars or other planetary atmospheres such as Venus and Titan.
•A microphone and two sound sources are used to study sound propagation on Mars.•Atmospheric turbulence scatters the acoustic signals recorded on Mars.•The amplitude scattering follows the daytime turbulence pattern.•Sounds intensity varies by a factor of 1.8 over a Martian year.•The sound amplitude evolution with distance matches with the sound attenuation model.
The meteorological package (MET) on the Phoenix Lander is designed to provide information on the daily and seasonal variations in Mars near‐polar weather during Martian late spring and summer. The ...present paper provides some background on the temperature, pressure, and wind instrumentation on the Phoenix MET station and their characterization. A separate paper addresses the MET lidar instrument. Laboratory studies in a Mars wind tunnel confirm estimates that the time constant of the thermocouples should be less than 0.5 s for wind speeds of 5 m s−1 or greater. Solar radiation falling on the thermocouples could raise the reported temperatures by up to 0.7 K for wind speeds of 5 m s−1. The increase will be wind speed dependent and will increase to 0.8 K at U = 3 m s−1 under peak solar radiation. Pressure sensors will give Mars surface pressures accurate to 10 Pa or better while Telltale deflections should provide reliable wind speed information up to at least 10 m s−1. The paper also discusses, to a limited extent, how the MET instruments will be used in conjunction with other instruments on the Phoenix Lander to provide an enhanced meteorological data set. We also describe instrumentation related to the Atmospheric Structure Experiment during entry, descent, and landing (EDL). These instruments will provide deceleration data. Together with drag coefficient information and a surface pressure measurement from MET, these data will allow us to infer the density, pressure, and temperature structure throughout the vertical column during EDL.
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