Humidity calibration of relative humidity devices in Martian conditions

Finnish Meteorological Institute (FMI) has developed relative humidity measurement devices for past and future Mars lander missions: REMS-H for Curiosity, MEDA HS for Mars 2020 and METEO-H for ExoMars 2020. The sensors used in these devices are HUMICAP® capacitive thin-film polymer sensors by Vaisala Inc. New calibration measurements are performed with ground reference models of these devices in the Mars Simulation Facility (MSF) and Planetary Analog Simulation Laboratory (PASLAB) at the German Aerospace Center (DLR) in spring 2020. The preliminary results will be given at the EGU 2020. Calibration of relative humidity devices requires in minimum two humidity points over the expected operational temperature and pressure range of the device. With two-point calibration the relative humidity devices can be used for scientific measurements with satisfactory quality but the uncertainty is notable. Stable humidity conditions between dry and saturation humidity in Martian conditions can be achieved reliably in very few laboratories in the whole world and humidity measurements in Martian conditions have been previously performed for the same devices in FMI laboratory and in Michigan Mars Environmental Chamber (MMEC) at the University of Michigan. The new measurement campaign will consist of stable humidity point measurements in multiple temperatures between +10°C to -70°C in CO2 gas and Martian pressure of approximately 7 hPa. The measurements are performed simultaneously for multiple devices in a small pressure vessel with continuous humidified carbon dioxide flow. The new measurement campaign will improve the characterization of the existing relative humidity devices in Mars lander missions and define in more detail the measurement uncertainties

Calibration and first results of relative humidity sensor MEDA HS onboard M2020 rover

MEDA HS is the relative humidity sensor on the Mars 2020 Perseverance rover provided by theFinnish Meteorological Institute (FMI). The sensor is a part of Mars Environmental DynamicAnalyzer (MEDA), a suite of environmental sensors provided by Centro de Astrobiología in Madrid,Spain. MEDA HS, along with METEO-H in ExoMars 2022 surface platform, is a successor of REMS-Hon board Curiosity.Calibration of relative humidity (RH) instruments for Mars missions is challenging due to the rangeof RH (from 0 to close to 100%) and temperature conditions (from about -90 ºC to + 22 ºC) thatneed to be simulated in the lab. Thermal gradients in different parts of the system need to be wellknown and controlled to ensure reliable reference RH readings. For MEDA HS the calibration testshave been performed for different models of MEDA HS in three Martian humidity simulatorlaboratories: FMI laboratory, Michigan Mars Environmental Chamber (MMEC) and DLR PASLAB(Planetary Analog Simulation Laboratory). MEDA HS flight model was tested at FMI together with flight spare and ground reference models inlow pressure dry CO2 gas from +22ºC to -70ºC and in saturation conditions from -40ºC down to-70ºC. Further, the MEDA HS flight model final calibration is complemented by calibration datatransferred from an identical ground reference model which has gone through rigorous testingalso after the flight model delivery. During the test campaign at DLR PASLAB that started inAutumn 2020, MEDA HS has been calibrated over the full relative humidity scale between -70 to-40ºC in CO2 in the pressure ranges from 5.5 to 9.5 hPa, representative of Martian surfaceatmospheric pressure. The results can be extrapolated to higher and lower temperatures.In this presentation the final flight calibration and performance of the MEDA HS will be presentedtogether with first results expected from the surface of Mars by the Perseverance rover

ESA Dragliner - Coulomb drag based telecommunication satellite deorbiting device

editorial reviewedDragliner is an ESA project to design, manufacture, assemble and test a breadboard model of a tether-based deorbiting system for Low Earth Orbit (LEO) telecommunication satellite deorbit. It is led by the Finnish Meteorological Institute, and the consortium also contains Aurora Propulsion Technologies, GRADEL and University of Luxembourg. The chosen technology is the plasma brake microtether, which is an emerging propellantless and efficient deorbiting solution utilizing Coulomb drag to deorbit satellites in LEO. The system is very lightweight, small in size and requires little power. It is furthermore autonomous and requires no resources from the carrying satellite during deorbiting. The main goal of the project is to increase the TRL of the satcom plasma brake to 4. This consists of choice of deployment strategy, configuration of the deorbit system, choosing the material for the tether, finalizing the geometry for the tether, simulations for deorbiting performance as well as tether dynamics, tests conducted on the tether material in zero-gravity laboratory and the initial breadboard model design of the most critical components of the deorbit system. These include the reels for main tether, the main tether itself, as well as a supporting tape tether and it's housing. Current deployment strategy, design trade-offs, material selections, most critical components and simulation results will be showcased

The MetNet vehicle : a lander to deploy environmental stations for local and global investigations of Mars

Investigations of global and related local phenomena on Mars such as atmospheric circulation patterns, boundary layer phenomena, water, dust and climatological cycles and investigations of the planetary interior would benefit from simultaneous, distributed in situ measurements. Practically, such an observation network would require low-mass landers, with a high packing density, so a large number of landers could be delivered to Mars with the minimum number of launchers. The Mars Network Lander (MetNet Lander; MNL), a small semi-hard lander/penetrator design with a payload mass fraction of approximately 17 %, has been developed, tested and prototyped. The MNL features an innovative Entry, Descent and Landing System (EDLS) that is based on inflatable structures. The EDLS is capable of decelerating the lander from interplanetary transfer trajectories down to a surface impact speed of 50-70 ms(-1) with a deceleration of <500 g for <20 ms. The total mass of the prototype design is approximate to 24 kg, with approximate to 4 kg of mass available for the payload. The EDLS is designed to orient the penetrator for a vertical impact. As the payload bay will be embedded in the surface materials, the bay's temperature excursions will be much less than if it were fully exposed on the Martian surface, allowing a reduction in the amount of thermal insulation and savings on mass. The MNL is well suited for delivering meteorological and atmospheric instruments to the Martian surface. The payload concept also enables the use of other environmental instruments. The small size and low mass of a MNL makes it ideally suited for piggy-backing on larger spacecraft. MNLs are designed primarily for use as surface networks but could also be used as pathfinders for high-value landed missions.Peer reviewe

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with -1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.Peer reviewe

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with - 1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.</p

The quality of the Mars Phoenix pressure data

The Phoenix lander operated on the surface of Mars for circa 5 months in 2008. One of its scientific instruments is an atmospheric pressure sensor called MET-P. We perform a comprehensive study to identify all error sources affecting the data measured by MET-P and to generate methods for compensating these errors. Our results show that MET-P performed much better than was reported immediately after the mission (Taylor et al., 2010). The error limits of the original calibrated Phoenix pressure data currently available in NASA's Planetary Data System (Dickinson, 2008) are from −5.3 Pa to +3.5 Pa. Further, almost no temperature-dependent error exists in the original calibrated MET-P data. However, we identify a previously unknown error source, temperature hysteresis, which causes minor peaks in the measured pressure curve (<0.4 Pa). The electronic supplementary material of this article contains a version of the Phoenix pressure data generated by applying all the error compensations developed in this study (Online Resource 1). The study is based on the re-analysis of the original test data of MET-P, the analysis of the engineering data measured during the mission on Mars and during the interplanetary cruise, and laboratory tests with the Reference Model of the MET-P sensor. Temperature dependent errors are evaluated by comparing the readings of two sensor heads with different sensitivities, measuring the same quantity. The principle of this method is applicable also for other types of instruments.Peer reviewe

Plasma Brake for Deorbiting Telecommunication Satellites

peer reviewedDragliner is an ESA project to design, manufacture, assemble and test a breadboard model of a tether-based deorbiting system for Low Earth Orbit (LEO) telecommunication satellite deorbiting. The consortium for the project is led by the Finnish Meteorological Institute, and it also contains Aurora Propulsion Technologies, GRADEL and University of Luxembourg. The chosen technology is the plasma brake microtether, which is an emerging propellantless and efficient deorbiting solution utilizing Coulomb drag to deorbit satellites in LEO. In this project, a microtether is defined as a tether that does not exceed the mass limit of 200 milligrams per meter, which makes it safe to other space assets in the event of a collision. Though in this project, the actual mass is approximately 20 milligrams per meter, which is even lower. The plasma brake is a very thin negatively charged microtether which, when charged, causes a braking force by creating enhanced Coulomb drag with the ambient ionospheric plasma ram flow. Though the fully deployed system is of considerable size (current estimates in the range of 5 km), the system is very lightweight, small in volume at the carrying satellites end, and requires little power. It is furthermore autonomous and requires no resources from the carrying satellite during deorbiting. The system is safe to other assets in space despite its significant size, as the tether itself is of very small mass. In case of a possible impact with another satellite, the microtether impact will cause damage similar to micrometeoroid flux experienced in LEO conditions. The plasma brake microtether should be differentiated from the more well-known electrodynamic tether, as the plasma brake is much thinner and uses electrostatic drag as opposed to magnetic forces. The main goal of the project is to increase the TRL of the telecommunication satellite plasma brake to 4. This consists of choice of deployment strategy, configuration of the deorbit system, choosing the material for the tether, finalizing the geometry for the tether, simulations for deorbiting performance as well as tether dynamics, tests conducted on the tether material in zero-gravity laboratory and the initial breadboard model design of the most critical components of the deorbit system. These include the reels for main tether, the main tether itself, as well as a supporting tape tether and it's housing. Current deployment strategy, design trade-offs, material selections, most critical components and simulation results will be showcased. The system utilizes two different tethers, the main tether which is the Coulomb drag plasma brake microtether. The other one is a tape tether, which is significantly shorter and is used to provide an electron gathering surface area for the main tether functionality. The deployment of the tether presents several challenges as tethers in space have historically been very difficult to operate. The reliability of the system must be very high, and in case of deorbiting failure space debris hazard must be minimized and any debris parts must be trackable

MEDA HS : Relative humidity sensor for the Mars 2020 Perseverance rover

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 Astrobiolog´ıa. 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