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In October 2018, MASCOT landed on the surface of Ryugu to start a campaign of in-situ measurements. Its brief mission was successful, with the onboard camera revealing the surface of this C-type asteroid in unpre- cedented detail. The presence of abundant mm-sized, multi-colored inclusions in one rock suggests a link between Ryugu and carbonaceous chondrites.

A Mobile Asteroid Surface Scout (MASCOT) on the Hayabusa 2 Mission to Ryugu

The DLR-ESTEC GOSSAMER roadmap envisages the development of solar sailing by successive low-cost technology demonstrators towards first science missions. In this framework, the GOSSAMER-1 deployment demonstrator for a (5 m)² sail structure in low Earth orbit is followed by a (20 m)² sail effect demonstrator GOSSAMER-2 for higher Earth orbits, and the (50 m)² GOSSAMER-3 sailcraft to prove the principle within the Earth-Moon system. Missions requiring the unique capabilities of solar sail propulsion were studied by science working groups, including multiple NEO rendezvous and fly-by. The GOSSAMER sail technology has been developed by DLR since the 1990s, with a successful (20 m)² deployment test in 1999 at DLR Cologne. The requirements for GOSSAMER-3 demand the demonstration of sufficient trajectory and attitude control for science missions. Advances in boom, sail, and deployment mechanisms have already now increased the payload margin of baseline GOSSAMER-3 designs from a few to several kg. A camera to demonstrate attitude control and a magnetometer to study the space environment around a sail were first considered as payloads for GOSSAMER-3. In addition to these, the shoebox-sized 10 kg asteroid lander MASCOT recently launched with HAYABUSA-2 also carries a hyperspectral infrared soil microscope and a surface thermal infrared radiometer. The camera‘s and radiometer‘s fields of view coincide on the asteroid surface. Although designed for a mission on (162173) 1999 JU3, with the necessary margins for the unknown the instruments are versatile enough to adapt. Thus, a minimal modification of MASCOT may be integrated as separable instrument module with GOSSAMER-3, first to observe the sail during the deployment and demonstration flight phases. In an extended mission and with experience previously gained, the mission could be concluded by the rendezvous with and the challenging drop of a ballistic lander onto a small asteroid near Earth. For the exercise scenario on the mitigation of fictional Earth impactor 2015 PDC, it is assumed that the GOSSAMER roadmap keeps its 2 year mission interval after the last expected launch date for GOSSAMER-1; the HAYABUSA-2 mission proceeds successfully; the MASCOT Flight Spare become Ground Reference Model is preserved flightworthy and released from duty ½ year after the landing of MASCOT on 1999 JU3 to be mated to a likely GOSSAMER-3 design prepared for but not depending on this opportunity. The combined spacecraft may: fly a technology demonstration mission extended to end at a nearby NEA; proceed directly to 2015 PDC for a fast flyby, a rendezvous and lander drop, or both; or abort the already begun tech-demo mission and midways change course towards the newly recognized threat.

A Mobile Asteroid Surface Scout (MASCOT) for the Hayabusa 2 Mission to 1999 JU3: The Scientific Approach

A small lander, MASCOT, is being developed at DLR (German Aerospace Center), with contributions from CNES, for JAXA’s HAYABUSA-2 mission. MASCOT will carry a multispectral imager (MASCOT-Cam), provided by DLR’s Institute of Planetary Research.

Im Rahmen der vorliegenden Dissertation wurden mehrere Sensoren zur Detektion des atmosphärischen Wassergehaltes entwickelt und für ihren Einsatz auf dem Mars im Zuge der ESA ExoMars Mission optimiert und teilweise qualifiziert. Die Arbeiten am als MiniHUM bezeichneten Instrument umfassten sowohl die Charakterisierung und Entwicklung eines coulometrischen Sensorsystems als auch den Test und die Auswahl von kommerziell erhältlichen kapazitiven Polymerfeuchtesensoren. Zudem wurde ein Sensor zur Detektion der Phasenumwandlungstemperatur qualitativ untersucht. In der vorliegenden Arbeit standen insbesondere die wissenschaftlichen Problem- und Fragestellungen des coulometrischen Sensors im Fokus. Durch eine Veränderung von Sensorbeschichtung, Sensorlayout und Betriebsart ist es während der Dissertation gelungen, dessen Reproduzierbarkeit, Genauigkeit und Langzeitstabilität bei Unterdruck und Tieftemperaturen, aber auch unter Normalbedingungen signifikant zu erhöhen und die Standzeiten deutlich zu verlängern. Die gefundenen Ergebnisse und Technologien konnten als Spin-off im Projekt HUMITRACE in Zusammenarbeit mit einem KMU dazu verwendet werden, eine neue Generation von industriellen Spurenfeuchtetransmittern bis zur Marktreife zu entwickeln. Ein weiterer Schwerpunkt dieser Arbeit war die Erstellung und experimentelle Validierung eines numerischen CFD-Modells, mit dem die Wasserdampfdiffusion durch die am coulometrischen Sensor verwendete permeable Membran und die Auswirkungen der elektrolytischen Aufspaltung des Wassers am Sensor simuliert werden können. Somit wird es möglich, den Sensor in komplexe Simulationen einzubinden und so beispielsweise die Auswirkungen von Landeraufbauten, Airbag und unterschiedlichen thermischen Umgebungen auf das Sensorsignal zu untersuchen. Neben den coulometrischen Sensoren wurden auch zwei kommerzielle kapazitive Polymerfeuchtesensoren sowohl unter Marsbedingungen als auch im Thermalzyklustest geprüft und charakterisiert. Die verwendeten Modelle zeigten trotz der extremen Bedingungen eine stabile Kennlinie und bewiesen, dass die Sensoren in Umgebungen einsetzbar sind, welche deutlich von dem Messbereich abweichen, für den sie entwickelt wurden. Zusätzlich zu den Entwicklungsarbeiten wurde im Zuge der ExoMars Mission ein erster Prototyp des MiniHUM Instrumentes konstruiert und gebaut. Zusammen mit der für ein Raumfahrtprojekt nötigen Dokumentation nach ECSS Standard, mit deren Hilfe der Nachweis geführt wurde, dass das Instrument den raumfahrttechnischen Anforderungen entspricht und alle Management-, Produkt- und Qualitätssicherungsmaßgaben eingehalten wurden, konnte in einem Gutachten der ESA ein Technologiereifegrad von 5 erreicht werden., Liquid water on Earth is essential for physical, chemical and in particular for biological processes. During the last decade results from several missions to Mars had shown evidences of possible liquid or liquid like water adsorbed to the Regolith causing rheological activities such as seepage phenomena and light toned deposits within gullies similar to mudflow phenomena on Earth. The NASA Phoenix-Mission had found water ice beneath the upper Regolith layers as well as evidences of saline brine formation. The existence of liquid or undercooled liquid interfacial water could have led to the formation of oxygenate molecules and therefore being one reason for the highly oxidized surface observed on Mars. Moreover, laboratory experiments have shown that metabolic activities are still detectable at environmental conditions similar to those on Mars, if one or two monolayers of water are present. In this study, several sensors had been developed and tested for measuring the near surface atmospheric water content in preparation on the former ESA ExoMars mission. The sensors, which were part of the MiniHUM instrument have been optimized and partly qualified for their mission on Mars. The work comprises the design and development of a coulometric sensor system as well as trade-off studies for commercial-of-the-shelf capacitive humidity sensors. Further, a sensor for detecting atmospheric frost point temperatures has been analysed quantitatively. The thesis mainly focuses on unsolved issues on characteristics and behaviour of the coulometric sensor detected during first measurements under martian environmental conditions. The problems could be comprehensively solved and long-term repeatability, accuracy and response time at low pressures and temperatures as well as under normal environmental conditions had been improved significantly by variation of sensor layout, -coating and the operating procedure. Further, the overall lifetime could be extended. In a jointed project together with a SMU, the spin-off of techniques and technologies has been used for developing a next generation coulometric sensor (HUMITRACE) mainly for industrial applications. At the time of submitting the thesis the sensor is on the verge of being launched into the market and was also being presented on several fairs. The second major objective of this study was the numerical simulation of water vapour diffusion through porous media and the electrolysis of water by means of computational fluid dynamics (CFD). In a first step Viscous-, Knudsen- and continuum-diffusion were implemented by determining experimentally parameters such as permeability and obstruction factor. After the numerical model had been validated by simultaneously conducted experiments, the electrolysis of water has been applied to the model based on experimental data as well. The "'numerical"' Instrument than was included into complex models for simulating its behaviour under martian environmental conditions. Thus, it is possible to determine the effects of e.g. lander structure or deflated airbag onto the sensor signal, including wind, solar irradiation, convection and hence, also the impact to scientific objectives of the instrument. First successfully attempts were made to include the ExoMars landing module and the "numerical"' MiniHUM sensor into a model for simulating the exchange processes between Regolith and atmosphere developed by the University of Alberta - but the created models needs to be further validated by domain and mesh independence analyses. In addition to the laboratory and numerical work described above first prototypes of MiniHUM were built in accordance to standards of ECSS and requirements given by ExoMars. The instrument has reached a technology readiness level (TRL) of five after it had passed the preliminary design review.

In diesem Beitrag wird das Projekt TNS-Normungsprojekt SMADLUSEA vorgestellt. In diesem Projekt sollen Vorschläge für die messtechnischen Anforderungen erarbeitet werden, die für die Messung des Druckes, der Temperatur und primär der Gaseuchte (relative und absolute Feuchte) angewendet werden sollten, um unter extremen Bedingungen, d.h.: - Gasfeuchte zw. -20°C Frostpunkt bis -100°C Frostpunkt, - Temperatur zw. 50°C und -75°C, - Druck zw. 1013 hPa und 6 hPa zuverlässig messen zu können. Im Idealfall ensteht am Ende das Projektes ein Normentwurf zur Veröffentlichung im DIN, ISO oder anderen.

Mars is a frozen desert planet. Considerable intense UV radiation fluxes reach its surface and with its thin and 95 % CO2 rich atmosphere and an atmospheric pressure of approximately 6 mbar this planet is not supposed to be habitable. But according to a variety of different experiments during the last decade where microorganisms were investigated under Mars-like environmental conditions there is evidence that even recent Mars appears to be a habitable planet. The habitability of the surface and upper subsurface of Mars depends on one hand on the viability and adaptation capacity of microorganisms under Mars-like environments and on the other hand on the planet's energy resources and liquid water availability. Besides chemical, inorganic energy sources in the soil intense solar radiation is available as additional energy source on the surface of Mars but might be harmful for most of known terrestrial life forms. However, previous studies on extremophilic microorganisms which were performed on space exposure platforms (e.g. BIOPAN on the satellite FOTON and EXPOSE on ISS) show the high resistance of tested bacteria, archaea and lichens to space radiation and desiccation caused by vacuum. During Mars simulation experiments photosynthesizing microorganisms are even able to do photosynthesis periodically. The periodicity of the photosynthetic activity depends on the diurnal cycle with its varying temperatures and relative humidity. It is important to emphasize that the aforementioned space resistant microorganisms are mainly collected in polar and alpine habitats. They are living in permafrost regions with high UV radiation income and extreme dryness provoking high adaptation strategies. Because of these environmental parameters the alpine, desert and polar habitats were characterized as Mars analogue. The Mars analogy of these regions can also be justified by comparing the colonized alpine and polar field profiles with surface structures on Mars. Numerous investigations were done during field campaigns in the Alps, the Arctic (Svalbard) and in Antarctica. Based on these field investigations it becomes obvious that gullies, polygon rich regions and micro caves, fissures and cracks in rocks can be seen as suitable candidates for habitable areas on the surface of Mars in addition to the supposed ice rich environment in the subsurface. As mentioned above, the habitability of Mars depends also on the availability of liquid water. Due to the presence of salts and perchlorate rich soils on Mars water can for sufficient relative humidity remain in a liquid phase, forming at least temporary liquid cryobrines far below the freezing point, which e.g. might be useful for some halophilic microorganisms. This may be in favour of the habitability of the Martian surface. In addition the habitability can also be influenced by the sorption and desorption capacity of other soil particles. These particles and salty solutions could avoid or enhance the liquid phase of water. Processes enhancing the liquefaction of water might explain the recently observed rheological events provoking e.g. the formation of gullies on the surface of Mars which are known as real habitats for a diversity of microorganisms on terrestrial martian analogue environments mostly present in the polar regions. All presently enumerated factors are positively emphasizing that habitability of recent Mars is particularly probable for some of terrestrial life forms.

The technology transfer project HUMITRACE exemplarily demonstrates successful transfer of space-technique applications via appropriate modification to competitive products. These are finally based on technical developments for scientific space experiments at DLR-PF (DLR Institute of planetary research), and have correspondingly been modified and manufactured in cooperation with an industrial partner.

Extensive measurements of commercial capacitive polymeric humidity sensors were made at temperatures ranging from 73 °C to 20 °C and at a pressure of 800 Pa in order to test and validate their performance for future space missions. We found the sensor signal decreases when temperature decreases as well as a temperature independent sensor characteristic in the range from 0 %RH to 30 %RH. In addition the sensor has shown stable characteristics during thermal cycling in the range from 120 °C to 20 °C under vacuum conditions.

The water content of soils significantly influences their chemical, physical and biological properties. In respect of Mars the thin layer of the upper millimetres of the Martian surface are of particular interest since this soil interacts directly with the diurnally varying atmospheric humidity, which can reach saturation during night and early morning. Adsorption/desorption of water in the soil and freezing of it can be a consequence. Therefore, near-surface measurements of the atmospheric content of water vapour will allow to investigate the interaction between the atmosphere and the adsorbed water, which is deposited in the upper soillayer. This should be an important point in respect of exobiology and the exploration of Mars. The Institute of Planetary Research at the German Aerospace Center and the SMB Dr. Wernecke & Partner are jointly developing a humidity sensor system in preparation for the ExoMars mission. Its goal is to obtain first in-situ measurements of diurnal and seasonal variations of the near-surface atmospheric water vapour content. By consequent miniaturization the MiniHUM Team was able to reduce size and weight of the coulometric sensor in such a way that the system, weighting 180g, will be one of the smallest instruments on board of the ExoMars mission. The instrument itself consists of two different units: HUM and ASS. The humidity sensor HUM is a combined unit of the coulometric sensor (QSE) and a capacitive (CPS) humidity sensor with an integrated thermocouple. The unit will be placed inside a small sensor housing (55 x 48 x 9 mm³) on the outer solar panel of the lander structure. For measuring the humidity under Martian conditions the principles of coulometric and capacitive measurement are the most appropriate. The coulometric principle is based on the ability of Diphosphorpentoxid (P2O5) to adsorb environmental water vapour almost completely, generating finally HPO3 in solution. In case of a sufficiently applied DC voltage this leads to a resulting electric current due to charge separation in the solution. The resulting current is directly related to the amount of adsorbed water, as described by Faraday´s law. This offers the possibility to quantitatively measure absolute humidity in the dew-point range between –90° C and -40°C. The capacitive humidity sensor uses the humidity dependence of some polymeric dielectrics to measure the relative humidity content of environmental gas from 5% r.h to 80% r.h. By using the two different principles of measurement it is possible to ensure a wide working range but also redundancy and a cross-reference for each sensor. The Atmosphere Saturation Sensor (ASS) will be mounted externally and consists of a high sensitive resistant thermometer for independent determination of the frost point temperature. The measurement of the frost point temperature will give an additional and independent way to determine absolute humidity, specifically at that point of phase transition (cf. Ryan and Sharman, 1981). This information can also be used for calibration purposes of the humidity sensors.

Physical interaction with small solar system bodies (SSSB) is key for in-situ resource utilization (ISRU). The design of mining missions requires good understanding of SSSB properties, including composition, surface and interior structure, and thermal environment. But as the saying goes "If you've seen one asteroid, you've seen one Asteroid": Although some patterns may begin to appear, a stable and reliable scheme of SSSB classification still has to be evolved. Identified commonalities would enable generic ISRU technology and spacecraft design approaches with a high degree of re-use. Strategic approaches require much broader in-depth characterization of the SSSB populations of interest to the ISRU community. The DLR-ESTEC GOSSAMER Roadmap Science Working Groups identified target-flexible Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the missions only feasible with solar sail propulsion, showed the ability to access any inclination and a wide range of heliocentric distances as well as continuous operation close to Earth's orbit where low delta-v objects reside.

Physical interaction with small solar system bodies (SSSB) is the next step in planetary science, planetary in-situ resource utilization (ISRU), and planetary defense (PD). It requires a broader understanding of the surface properties of the target objects, with particular interest focused on those near Earth. Knowledge of composition, multi-scale surface structure, thermal response, and interior structure is required to design, validate and operate missions addressing these three fields. The current level of understanding is occasionally simplified into the phrase, ”If you’ve seen one asteroid, you’ve seen one asteroid”, meaning that the in-situ characterization of SSSBs has yet to cross the threshold towards a robust and stable scheme of classification. This would enable generic features in spacecraft design, particularly for ISRU and science missions. Currently, it is necessary to characterize any potential target object sufficiently by a dedicated pre-cursor mission to design the mission which then interacts with the object in a complex fashion. To open up strategic approaches, much broader in-depth characterization of potential target objects would be highly desirable. In SSSB science missions, MASCOT-like nano-landers and instrument carriers which integrate at the instrument level to their mothership have met interest. By its size, MASCOT is compatible with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap Science Working Groups‘ studies identified Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. The Solar Polar Orbiter (SPO) study showed the ability to access any inclination, theDisplaced-L1 (DL1) mission operates close to Earth, where objects of interest to PD and for ISRU reside. Other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter, and significant progress has been made to explore the performance envelope of near-term solar sails for MNR. However, it is difficult for sailcraft to interact physically with a SSSB. We expand and extend the philosophy of the recently qualified DLR Gossamer solar sail deployment technology using efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions by synergetic integration and operation of sail and lander. The MASCOT design concept and its characteristic features have created an ideal counterpart for thisand has already been adapted to the needs of the AIM spacecraft, former part of the NASA-ESA AIDA mission. Designing the combined spacecraft for piggy-back launch accommodation enables low-cost massively parallel access to the NEA population.

Physical interaction with small solar system bodies (SSSB) is the next step in planetary science, planetary in-situ resource utilization (ISRU), and planetary defense (PD). It requires a broader understanding of the surface properties of the target objects, with particular interest focused on those near Earth. Knowledge of composition, multi-scale surface structure, thermal response, and interior structure is required to design, validate and operate missions addressing these three fields. The current level of understanding is occasionally simplified into the phrase, "If you've seen one asteroid, you've seen one Asteroid", meaning that the in-situ characterization of SSSBs has yet to cross the threshold towards a robust and stable scheme of classification. This would enable generic features in spacecraft design, particularly for ISRU and science missions. Currently, it is necessary to characterize any potential target object sufficiently by a dedicated pre-cursor mission to design the mission which then interacts with the object in a complex fashion. To open up strategic approaches, much broader in-depth characterization of potential target objects would be highly desirable. In SSSB science missions, MASCOT-like nano-landers and instrument carriers which integrate at the instrument level to their mothership have met interest. By its size, MASCOT is compatible with small interplanetary missions. The DLR-ESTEC Gossamer Roadmap Science Working Groups' studies identified Multiple Near-Earth asteroid (NEA) Rendezvous (MNR) as one of the space science missions only feasible with solar sail propulsion. The Solar Polar Orbiter (SPO) study showed the ability to access any inclination and a wide range of heliocentric distances, with a separable payload module delivered by sail to the proper orbit. The Displaced-L1 (DL1) spaceweather early warning mission study sailcraft operates close to Earth, where all objects of interest to PD must pass and low delta-v objects for ISRU reside. Other studies outline the unique capability of solar sails to provide access to all SSSB, at least within the orbit of Jupiter, and significant progress has been made to explore the performance envelope of near-term solar sails for MNR. However, it is difficult for sailcraft to interact physically with a SSSB. We expand and extend the philosophy of the recently qualified DLR Gossamer solar sail deployment technology using efficient multiple sub-spacecraft integration to also include landers for one-way in-situ investigations and sample-return missions by synergetic integration and operation of sail and lander. The MASCOT design concept and its characteristic features have created an ideal counterpart for this. For example, the MASCOT Mobility hopping mechanism and its power supply concept have already been adapted to the specific needs of MASCOT2 which was to be carried on the AIM spacecraft of ESA as part of the NASA-ESA AIDA mission to binary NEA Didymos. The methods used or developed in the realization of MASCOT such as Concurrent Engineering, Constraints-Driven Engineering and Concurrent Assembly Integration and Verification enable responsive missions based on now available as well as near-term technologies. Designing the combined spacecraft for piggy-back launch accommodation enables low-cost massively parallel access to the NEA population.