Forced convective heat transfer from three horizontally inclined rectangular-based cylinders (rods) has been studied experimentally under representative Martian near-surface air flows in the Aarhus Wind Tunnel Simulator (AWTS), Denmark. The testing campaign was developed for the HABIT (Habitability: Brines, Irradiation and Temperature) instrument, European payload on board the ExoMars 2022 Kazachok surface platform. The average heat transfer coefficient was determined from steady CO₂ flows at a pressure of 9.9 mbar, an ambient temperature of ∼25 °C, and for horizontal free-stream velocities between 0.8 and 12 m/s. A retrieval algorithm to derive the wind speed from the average heat transfer coefficient estimated at each of the three HABIT Air Temperature Sensors (ATS) rods was calibrated within the AWTS. The ATS rods are placed one at the front of the instrument structure (ATS₂) and two on the sides (ATS₁ and ATS₃); and under Martian atmospheric conditions these rods serve as cooling fins. Several relationships between the Nusselt number and the Reynolds and Prandtl numbers reported in the literature were evaluated to model convective heat transfer from the ATS rods. Where needed, corrections to account for radiative heat transfer within the AWTS were implemented. The final retrieval method demonstrated that wind speed can be retrieved for frontal winds in the range of 0–10 m/s, with an error of ±0.3 m/s, using the cooling profile of the ATS rod 3, and for lateral winds in the range of 0–6 m/s, with an error of ±0.3 m/s, using the ATS rod 2 cooling profile.

This work presents the development, validation and calibration of the air temperature sensors (ATS) and the air and wind retrieval method of the HABIT (HabitAbility: Brines, Irradiation and Temperature) instrument. HABIT is one of the two European  payloads of the ESA/Roscosmos ExoMars 2022 mission that will land at Oxia Planum (18.20° N, 335.45° E), on Mars.

One of the main novelties of this Ph.D. thesis is to use the thin fins that work as ATS on HABIT as a wind sensor for the planetary boundary layer of Mars. The thesis is based on the study and modelling of heat transfer along three rods when exposed to forced convection in a gaseous fluid, and that is tested: (1) through computational fluid dynamic simulations, which provided inputs to the early design of the HABIT structure; (2) under laboratory conditions, with the use of a specifically designed prototype and a cooling fan; and (3) within a subsonic wind tunnel facility under terrestrial conditions.

A preliminary validation of the wind speed retrieval approach is first performed using temperature measurements from Mars provided by the Rover Environmental Monitoring Station (REMS) instrument, on board the NASA Curiosity rover of the Mars Science Laboratory (MSL) mission. The method is based on modelling forced convection of the ATS of REMS when assumed as thin rods immersed in the extreme low-pressure and high-radiating atmospheric conditions of the Martian thermal boundary layer, at a height of ∼ 1.5 m from the surface. Assuming the previously reported REMS wind sensor (WS) retrieval errors of 20% for the wind speed, ±30° for the horizontal “front” wind directions, and ±45° for the horizontal “rear” wind directions, agreement with the WS values of up to 77% of the acquisition time, on average, for wind speeds and coincidence between 60% and 80% of the time for wind directions is reported for some sols. These promising results are limited to only evening extended acquisitions from 18:00 to 21:00 local mean solar time (LMST) and orientations within the validity region of the retrieval. That is, the method was only considered valid over a narrow angle range of 13° to 107° in azimuth angle. In addition to this, the results of this first study suggested a new optimal orientation when using the ATS for wind speed and direction retrievals of +60° clockwise with respect to the forward direction of the Curiosity rover.

The wind retrieval model is also validated and calibrated with the HABIT engineering and qualification model (EQM) in the Aarhus Wind Tunnel Simulator (AWTS) of the Aarhus University, Denmark. The AWTS is designed to reproduce typical winds on the surface of Mars. The data acquired during the wind tunnel campaign were used to validate the forced convective and radiative heat transfer model for each of the three ATS. The campaign investigated winds in steady CO2 flows at a pressure of 9.9 mbar, an ambient temperature of 25°C, and for horizontal free-stream velocities between 0.8 and 12 m/s. Several relationships between the Nusselt number and the Reynolds and Prandtl numbers reported in the literature were evaluated in the tunnel to model forced convection through the ATS rods. Where needed, corrections to account for radiative heat transfer within the AWTS were implemented to correct for experimental artefacts. The tests demonstrated that this retrieval method can be used to derive wind speed for frontal winds on Mars in the range of 0 to 10 m/s, with an error of ±0.3 m/s, using the cooling profile of the ATS rod 3, and for lateral winds in the range of 0 to 6 m/s, with an error of ±0.3 m/s, using the ATS rod 2 cooling profile.

The thesis also includes the calibration of the HABIT ATS flight model (FM) in the clean room of Omnisys Instruments AB, and the retrieval model that will be used in operations during the ExoMars 2022 mission and for archiving in the Planetary Science Archive (PSA) of the European Space Agency (ESA).

Finally, the wind retrieval method developed in this thesis can be applied not only to the future analysis of HABIT data at Oxia Planum, but also to re-analyse the ATS data of REMS at Gale crater, and for future comparative analysis with the HABIT/ExoMars 2022, the Temperature and Wind Sensors for InSight (TWINS)/InSight, and the Mars Environmental Dynamics Analyzer (MEDA)/Mars 2020 rover instruments.

This paper highlights unique sites in Ladakh, India, investigated during our 2016 multidisciplinary pathfinding expedition to the region. We summarize our scientific findings and the site's potential to support science exploration, testing of new technologies and science protocols within the framework of astrobiology research. Ladakh has several accessible, diverse, pristine and extreme environments at very high altitudes (3000–5700 m above sea level). These sites include glacial passes, sand dunes, hot springs and saline lake shorelines with periglacial features. We report geological observations and environmental characteristics (of astrobiological significance) along with the development of regolith-landform maps for cold high passes. The effects of the diurnal water cycle on salt deliquescence were studied using the ExoMars Mission instrument mockup: HabitAbility: Brines, Irradiance and Temperature (HABIT). It recorded the existence of an interaction between the diurnal water cycle in the atmosphere and salts in the soil (which can serve as habitable liquid water reservoirs). Life detection assays were also tested to establish the best protocols for biomass measurements in brines, periglacial ice-mud and permafrost melt water environments in the Tso-Kar region. This campaign helped confirm the relevance of clays and brines as interest targets of research on Mars for biomarker preservation and life detection.

The HABIT (HabitAbility: Brine Irradiation and Temperature) instrument is a European payload of the ExoMars 2022 Surface Platform Kazachok that will characterize the present-day habitability at its landing place in Oxia Planum, Mars. HABIT consists of two modules: (i) EnvPack (Environmental Package) that monitors the thermal environment (air and ground), the incident ultraviolet radiation, the near surface winds and the atmospheric dust cycle; and (ii) BOTTLE (Brine Observation Transition To Liquid Experiment), an In-situ Resource Utilization instrument to produce liquid water for future Mars exploration. BOTTLE will be used also to investigate the electrical conductivity properties of the martian atmosphere, the present-day atmospheric-ground water cycle and to evaluate if liquid water can exist on Mars in the form of brines, and for how long. These variables measured by HABIT are critical to determine the present and future habitability of the martian surface. In this paper, we describe in detail the HABIT instrument and sensors, together with the calibration of its Flight Model (FM) and the Engineering Qualification Model (EQM) versions. The EnvPack module has heritage from previous missions operating on the surface of Mars, and the environmental observations of its sensors will be directly comparable to those delivered by those missions. HABIT can provide information of the local temperature with ±0.2 °C accuracy, local winds with ±0.3 m/s, surface brightness temperature with ±0.8 °C, incident UV irradiance with 10% error of its absolute value in the UV-A, UV-B, UV-C ranges, as well as in the total UV-ABC range, and two additional wavebands, dedicated to ozone absorption. The UV observations can be used to derive the total opacity column and thus monitor the dust and ozone cycles. BOTTLE can demonstrate the hydration state of a set of four deliquescent salts, which have been found on Mars (calcium chloride, ferric sulphate, magnesium perchlorate and sodium perchlorate) by monitoring their electric conductivity (EC). The EC of the air and the dry salts under Earth ambient, clean room conditions is of the order of 0.1 μScm−1. We have simulated HABIT operations, within an environmental chamber, under martian conditions similar to those expected at Oxia Planum. For dry, CO2 atmospheric conditions at martian pressures, the air EC can be as low as 10−8 μScm−1, however it increases with the relative humidity (RH) percentage. The laboratory experiments show that after an increase from 0 to 60% RH within a few hours, the EC of the air increased up to 10−1 μScm−1, magnesium perchlorate hydrated and reached values of 10 μScm-1, whereas calcium chloride deliquesced forming a liquid state with EC of 102 μScm−1. HABIT will operate with a regular cadence, through day and night. The Electronic Unit (EU) is protected with a heater that is activated when its temperature is below −33 °C and disabled if the temperature of the surface platform rises above −30 °C. Additionally, the heaters of the BOTTLE unit can be activated to dehydrate the salts and reset the experiment. HABIT weighs only 918 g. Its power consumption depends on the operation mode and internal temperature, and it varies between 0.7 W, for nominal operation, and 13.1 W (when heaters are turned on at full intensity). HABIT has a baseline data rate of 1.5 MB/sol. In addition to providing critical environmental observations, this light and robust instrument, will be the first demonstrator of a water capturing system on the surface of Mars, and the first European In-Situ Resource Utilization in the surface of another planet.

This work presents a novel method for the real-time retrieval of wind speed on the surface of Mars that uses temperature measurements from the Rover Environmental Monitoring Station (REMS) instrument onboard the Curiosity rover of the Mars Science Laboratory (MSL) mission. After final failure of the Wind Sensor (WS) in sol 1491, REMS has not been providing wind data. The new wind retrieval approach that we propose may eventually be able to supply MSL with wind values for contextualizing the roverâôs operations and for meteorological studies on the surface of Mars. The new method is based on forced convection modeling of the Air Temperature Sensors (ATS) of REMS as thin rods immersed in the extreme low-pressure and high-radiating atmospheric conditions of the Martian thermal boundary layer at a height of ∼" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">∼ 1.5 m from the surface. A preliminary validation of the possibilities and limitations of this retrieval has been performed using comparative analysis with existing REMS wind field-site data for the same sols that are available at the Planetary Data System (PDS). We have developed both a ”coarse” approach, in which wind speed is determined with no regard to wind direction, and a ”refined” method, in which it is attempted to determine both wind speed and direction. Assuming the previously reported WS retrieval errors of 20% for the wind speed, we report an agreement to the WS values of wind speed ranging from 36.4% to 77% of the acquisition time for the ”coarse” approach, depending on the sol examined. These promising results are limited to only evening extended acquisitions from 18:00 to 21:00 local mean solar time (LMST). This method could be applied to daytime conditions. The results suggest a new optimal orientation for wind speed retrieval of 60°clockwise with respect to the forward direction of the Curiosity rover, although the technique is not yet ready to be considered for planning of the Curiosity rover operations. This method could extend the wind characterization of the Gale Crater for future Curiosity rover data acquisitions by recycling air temperature measurements and provide the scientific community with a data set for future comparative analysis with the Temperature and Wind Sensors for InSight (TWINS)/InSight, the HabitAbility: Brines, Irradiation and Temperature (HABIT)/ExoMars 2020, and the Mars Environmental Dynamics Analyzer (MEDA)/Mars 2020 rover instruments.

The deep subsurface of other planetary bodies is of special interest for robotic and human exploration. The subsurface provides access to planetary interior processes, thus yielding insights into planetary formation and evolution. On Mars, the subsurface might harbour the most habitable conditions. In the context of human exploration, the subsurface can provide refugia for habitation from extreme surface conditions. We describe the fifth Mine Analogue Research (MINAR 5) programme at 1 km depth in the Boulby Mine, UK in collaboration with Spaceward Bound NASA and the Kalam Centre, India, to test instruments and methods for the robotic and human exploration of deep environments on the Moon and Mars. The geological context in Permian evaporites provides an analogue to evaporitic materials on other planetary bodies such as Mars. A wide range of sample acquisition instruments (NASA drills, Small Planetary Impulse Tool (SPLIT) robotic hammer, universal sampling bags), analytical instruments (Raman spectroscopy, Close-Up Imager, Minion DNA sequencing technology, methane stable isotope analysis, biomolecule and metabolic life detection instruments) and environmental monitoring equipment (passive air particle sampler, particle detectors and environmental monitoring equipment) was deployed in an integrated campaign. Investigations included studying the geochemical signatures of chloride and sulphate evaporitic minerals, testing methods for life detection and planetary protection around human-tended operations, and investigations on the radiation environment of the deep subsurface. The MINAR analogue activity occurs in an active mine, showing how the development of space exploration technology can be used to contribute to addressing immediate Earth-based challenges. During the campaign, in collaboration with European Space Agency (ESA), MINAR was used for astronaut familiarization with future exploration tools and techniques. The campaign was used to develop primary and secondary school and primary to secondary transition curriculum materials on-site during the campaign which was focused on a classroom extra vehicular activity simulation.

Current forecasts suggest that, by 2030, at least 50% of telecommunication satellites will use electric propulsion (EP) as the only propulsion system on board. The ever-increasing operations time has led to a substantial increment of the amount of propellant stored on-board, from the initial 200-350 kg to present-day masses of 800-1500 kg. Despite the need to know the available propellant mass during operations, the retrieval is still challenging, and inaccurate, as no technological alternatives have been proven to satisfy with the needed requirements for long duration missions.

Recently we have proposed a new gauging method that uses TLR-9 hardware components. The method, called Improved-PVT method, is based on a better understanding of the thermal properties of the stored xenon. Laboratory experiments and theoretical work demonstrated an accuracy improved by a factor of 8 compared to classical Pressure-Volume-Temperature retrievals [A. Soria-Salinas et al., 2017]. In fact, it gives an error of mass gauging of 0.1% with respect to the initial mass, at a pressure of about 70 bar.

This method has been implemented in the PVT-GAMERS experiment, selected to fly at the ESA Fly Your Thesis! parabolic flight campaign, between October 22 nd to November 2 nd . As a technology demonstrator, it consists of a suit of 6 small-scaled and pressurized CO2 tanks, sensed with pressure (P) and temperature (T) sensors, with a heating duty cycle and real-time data processing. The PVT-GAMERS experiment will fly on three Airbus A310 Zero-G flights, where micro/hyper gravity-loads will allow to demonstrate the robustness of the method against thermal gradients, and i) simulated thruster ignitions, ii) external accelerations and iii) propellant management operations scenarios. These flights will also increase the TRL of the full system from 4 to 6.

In this work, we shall present the development, testing and ground calibration of the PVT-GAMERS experiment, including: 1) ground tests, assembly validation, expected results and operational procedures estimation; and 2) calibration of mass retrieval algorithm applied over a CO2 PVT-GAMERS engineering model (EM). Ground tests results indicates a relative error expected for the mass retrieval on flight model ground tests < 1.4% for CO2 gas at EOL conditions. Furthermore, a compromised solution shall be reached between retrieval expected accuracy, cooling rate for the retrieval application, and sensitivity to ambient condition changes. The EM tests suggest on this particular configuration to approximate the cooling ratio dP/dT using a least-squared-error procedure and over an interval of at least 900 seconds. 

The current state-of-the-art methods of mass gauging of Electric Propulsion (EP) propellants in microgravity conditions rely on external measurements that are taken at the surface of the tank. The tanks are operated under a constant thermal duty cycle to store the propellant within a pre-defined temperature and pressure range. We demonstrate using computational fluid dynamics (CFD) simulations that the heat-transfer within the pressurized propellant generates temperature and density anisotropies. This challenges the standard mass gauging methods that rely on the use of time changing skin-temperatures and pressures. We observe that the domes of the tanks are prone to be overheated, and that a long time after the heaters of the thermal cycle are switched off, the system reaches a quasi-equilibrium state with a more uniform density. We propose a new gauging method, which we call the Improved PVT method, based on universal physics and thermodynamics principles, existing TRL-9 technology and telemetry data. This method only uses as inputs the temperature and pressure readings of sensors externally attached to the tank. These sensors can operate during the nominal thermal duty cycle. The improved PVT method shows little sensitivity to the pressure sensor drifts which are critical towards the end-of-life of the missions, as well as little sensitivity to systematic temperature errors. The retrieval method has been validated experimentally with CO2 in gas and fluid state in a chamber that operates up to 82 bar within a nominal thermal cycle of 38 °C to 42 °C. The mass gauging error is shown to be lower than 1% the mass at the beginning of life, assuming an initial tank load at 100 bar. In particular, for a pressure of about 70 bar, just below the critical pressure of CO2, the error of the mass gauging in gas phase goes down to 0.1% and for 77 bar, just above the critical point, the error of the mass gauging of the liquid phase is 0.6% of initial tank load. This gauging method improves by a factor of 8 the accuracy of the standard PVT retrievals using look-up tables with tabulated data from the National Institute of Standards and Technology.