European Space Research And Technology Centre Research Articles

Investigation of long-term storage of space materials for future constellation missions: study of Braycote® 601 EF lubricant

The long-term storage (LTS) of space materials is becoming more and more critical for the next missions. For instance, for MTG (Meteosat Third Generation) mission, 5-year assemble, integration and testing (AIT) time on ground, up to 17.5-year storage for recurring models plus at least 8.5 years in orbit operation are planned. Hence, a good understanding of materials’ aging properties is desirable to ensure that materials’ specifications are still suitable after LTS, and, eventually, to anticipate the potential non-conformities. For this purpose, the European Space Research and Technology Centre (ESTEC) is investigating these problematics thanks to its wide capabilities from aging with environmental, climatic and vacuum chambers up to physico-chemical characterizations by numerous instruments such as microscopes, spectroscopes, thermal, mechanical or electrical analyzers. An overview is presented herein through the study of a fluorinated based grease lubricant named Braycote® 601EF widely used in mechanisms in space sector such as the US space shuttles actuator or the basic end effectors of The European Robotic Arm.

A novel device to study altered gravity and light interactions in seedling tropisms

Long-duration space missions will need to rely on the use of plants in bio-regenerative life support systems (BLSSs) because these systems can produce fresh food and oxygen, reduce carbon dioxide levels, recycle metabolic waste, and purify water. In this scenario, the need for new experiments on the effects of altered gravity conditions on plant biological processes is increasing, and significant efforts should be devoted to new ideas aimed at increasing the scientific output and lowering the experimental costs. Here, we report the design of an easy-to-produce and inexpensive device conceived to analyze the effect of interaction between gravity and light on root tropisms. Each unit consisted of a polystyrene multi-slot rack with light-emitting diodes (LEDs), capable of holding Petri dishes and assembled with a particular filter-paper folding. The device was successfully used for the ROOTROPS (for root tropisms) experiment performed in the Large Diameter Centrifuge (LDC) and Random Positioning Machine (RPM) at ESA's European Space Research and Technology centre (ESTEC). During the experiments, four light treatments and six gravity conditions were factorially combined to study their effects on root orientation of Brassica oleracea seedlings. Light treatments (red, blue, and white) and a dark condition were tested under four hypergravity levels (20 g, 15 g, 10 g, 5 g), a 1 g control, and a simulated microgravity (RPM) condition. Results of validation tests showed that after 24 h, the assembled system remained unaltered, no slipping or displacement of seedlings occurred at any hypergravity treatment or on the RPM, and seedlings exhibited robust growth. Overall, the device was effective and reliable in achieving scientific goals, suggesting that it can be used for ground-based research on phototropism-gravitropism interactions. Moreover, the concepts developed can be further expanded for use in future spaceflight experiments with plants.

Use of Moon Observations for Characterization of Sentinel-3B Ocean and Land Color Instrument

During the commissioning of the Sentinel-3B satellite, a single lunar observation was performed to assess the possible use of the moon for characterization and validation of onboard instruments. The observation was carried out in stable orientation after a roll maneuver, allowing the moon to be imaged by the Earth view of instruments. Data acquired by the Ocean Land Color Instrument (OLCI) allowed inflight verification of stray-light correction (SLC) performed by the Mission Performance Centre (MPC), and assessment of radiometric behavior of instrument in comparison with lunar irradiance models performed in cooperation between European Space Research and Technology Centre (ESTEC) and European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). This paper describes the results of those activities along with the proposed update of stray-light correction developed with the use of lunar data.

Dose Measurements and Simulations of the RADFETs Response Onboard the Alphasat CTTB Experiments

On July 25, 2013, the Alphasat satellite was launched, carrying the component technology test-bed (CTTB) to assess the space radiation effects in electronic components. Embedded in each of the three experimental boards of the CTTB, are radiation-sensitive metal-oxide–silicon field-effect transistors (RADFETs) to measure the radiation levels at the Alphasat geostationary orbit (GEO). In this work, values of accumulated dose are presented for the RADFETs onboard the Alphasat CTTB experiments up to July 16, 2018. These values were calculated from the threshold voltage shift and from temperature data transmitted to Earth, and using the model derived, previously, from the ESAPMOS4 RADFETs calibration campaign conducted at the European Space Research and Technology Centre (ESTEC) Cobalt-60 facility. These results show that the current accumulated doses are between 1.9 and 3.2 krad and the average dose rates are between 40 and 70 mrad/h. We also present a polynomial function that allows converting voltages into doses for a wide range of values and for different temperatures. The quality of this conversion is tested against Geant4 simulations of the expected dose in the CTTB components for the space radiation environment at the Alphasat orbit. The simulated doses were obtained for three GEO radiation models: AE8, AE9, and IGE-2006.

Multidisciplinary mission and system design tool for a reusable electric propulsion space tug

According to the Global Exploration Roadmap, a Getaway in the lunar vicinity will enable the human exploration of the Moon, paving the way toward Mars and further in the deep space. A reusable transportation system, the Lunar Space Tug (LST), can be a key support transportation system to achieve a continuous and sustainable connection between the Earth and the orbital lunar outpost. Exploiting an electrical propulsion technology consisting in Hall Thrusters (HTs), this reusable space cargo system can maximize the delivered payload, with a lower propellant consumption with respect to a chemical-based platform. This significant improvement comes with two main throwbacks: a long transfer time between Earth and Moon and a complex multidisciplinary design of the overall LST. The first issue can be overcome with good mission planning in order to reduce the layover times and maximize the use of the LST. However, the peculiarities of the adopted propulsion technology shape the overall mass and power distribution of the space tug, as well as its transfer trajectory. The design complexity introduced by this subsystem can be effectively investigated if the mission analysis, trajectory generation and subsystem sizing are merged together in one software. In fact, the low-thrust transfer trajectories are highly affected by orbital perturbation and eclipse periods. At the same time, the high demand in power of the propulsion system puts constraints on the mass breakdown and power allocations of the LST, therefore on the reachable thrust level. The trajectory and subsystems sizing limitations call for a particular accurate mission analysis in order to succeed. Only combining all those elements, it is possible to define feasible design boundaries without performing countless simulations trying to optimize each element as a stand-alone part.Politecnico di Torino, in collaboration with the European Space Research and Technology Centre (ESTEC), developed a MatLab-based preliminary design tool for electric propulsion space tug missions, called MultidisciplinAry desiGN Electric Tug tOol (MAGNETO). Starting from the mission analysis of the lunar space tug, the tool building blocks and capabilities are presented. Moreover, the build-in trajectory module will be analysed in-depth. The potentiality of the trajectory generation tool in MAGNETO enables a refined design of the initial design envelope of the LST. For this reason, the improved results will be confronted with the previous LST design tool developed by Politecnico di Torino.

Plasma beam structure diagnostics in krypton Hall thruster

AbstractKrypton Large Impulse Thruster (KLIMT) project was aimed at incremental development and optimization of a 0.5 kW-class plasma Hall Effect Thruster in which, as a propellant, krypton could be used. The final thermally stable version of the thruster (the third one) was tested in the Plasma Propulsion Satellites (PlaNS) laboratory in the Institute of Plasma Physics and Laser Microfusion (IPPLM) in Warsaw as well as in the European Space Agency (ESA) propulsion laboratory in the European Space Research and Technology Centre (ESTEC).During final measurement campaign, a wide spectrum of parameters was tested. The plasma potential, electron temperature, electron concentration, and electron energy probability function in the far-field plume of the thruster were measured with a single cylindrical Langmuir probe. Faraday probes were used for recording local values of ion current. Using several collectors in different locations and moving them on the surface of a sphere, the angular distribution of the expelled particles was reconstructed which was a local measure of beam divergence. Angular distribution of ion flux as measured with a central Faraday probe was parameterized with krypton mass flow rate, voltage, coil current ratio, and the cathode mass flow rate. Beam divergence measurements with Faraday probes as well as plasma parameters derived from Langmuir probe seem to be consistent with our understanding of the operating envelope. Obtained results will serve as a baseline in the design of plasma beam structure diagnostics system for the PlaNS laboratory.

The Strategic Role of Inter-Laboratory Comparison Among International Institutions to Assure Confidence: Report of the INRIM and the European Spatial Agency Comparison on Electrical Quantities

Inter-laboratory comparisons (ILCs) are an effective mean to establish the compatibility of the measurements among laboratories also belonging to different countries and so belonging to different measurement systems. As consequence, they are a mean to assure confidence in the competence and in the correctness of the unit dissemination processes from national Standards in different countries. This paper refers on an ILC between the National Institute of Metrological Research (INRIM-Italy) and the European Space Research and Technology Centre (ESA-ESTEC), belonging therefore to two different measurement systems, on DC Voltage, DC Resistance and Electrical Capacitance carried out in 2016. The comparison had satisfactory results.

3D thermography for improving temperature measurements in thermal vacuum testing

The application of thermography to thermal vacuum (TV) testing of spacecrafts is becoming a vital additional tool in the mapping of structures during thermal cycles and thermal balance (TB) testing. Many of the customers at the European Space Agency (ESA) test centre, European Space Research and Technology Centre (ESTEC), The Netherlands, now make use of a thermal camera during TB-TV campaigns. This complements the use of embedded thermocouples on the structure, providing the prospect of monitoring temperatures at high resolution and high frequency. For simple flat structures with a well-defined emissivity, it is possible to determine the surface temperatures with reasonable confidence. However, for most real spacecraft and sub-systems, the complexity of the structure’s shape and its test environment creates inter-reflections from external structures. This and the additional complication of angular and spectral variations of the spacecraft surface emissivity make the interpretation of the radiation detected by a thermal camera more difficult in terms of determining a validated temperature with high confidence and well-defined uncertainty. One solution to this problem is: to map the geometry of the test specimen and thermal test environment; to model the surface temperatures and emissivity variations of the structures and materials; and to use this model to correct the apparent temperatures recorded by the thermal camera. This approach has been used by a team from NPL (National Physical Laboratory), Psi-tran, and PhotoCore, working with ESA, to develop a 3D thermography system to provide a means to validate thermal camera temperatures, based on a combination of thermal imaging photogrammetry and ray-tracing scene modeling. The system has been tested at ESTEC in ambient conditions with a dummy spacecraft structure containing a representative set of surface temperatures, shapes, and spacecraft materials, and with hot external sources and a high power lamp as a sun simulator. The results are presented here with estimated temperature measurement uncertainties and defined confidence levels according to the internationally accepted Guide to Uncertainty of Measurement as used in the IEC/ISO17025 test and measurement standard. This work is understood to represent the first application of well-understood thermal imaging theory, commercial photogrammetry software, and open-source ray-tracing software (adapted to realize the Planck function for thermal wavebands and target emission), and to produce from these elements a complete system for determining true surface temperatures for complex spacecraft-testing applications.

Developing ePartners for human-robot teams in space based on ontologies and formal abstraction hierarchies

Manned space missions are typically performed by teams composed of humans as well as technical systems and are situated in complex, dynamic and safety-critical domains. Intelligent electronic partners (ePartners) can play an important role here to support human-robot teams in their collaborative problem solving process when things do not go as planned. To engage in effective team collaboration, ePartners, humans and robots must align their communication at the right level of abstraction. In this paper, an approach is put forward to represent the functionality of human-robot teams in a formal manner using abstraction hierarchies. In this way, formal relations between domain knowledge at the system, functional and mission-oriented levels are established and reasoning rules are used to navigate through these relations. As a consequence, ePartners are equipped with the ability to reason about the status of a mission, propose solutions in non-nominal situations and provide explanations for the proposed solutions. The approach has been implemented within a mobile application on a tablet that can be used to support astronaut-robot teams during space missions. The application has been evaluated during an experiment at the European Space Research and Technology Centre (ESTEC) in the context of a Mars mission.

Effects of hypergravity on the angiogenic potential of endothelial cells.

Angiogenesis, the formation of blood vessels from pre-existing ones, is a key event in pathology, including cancer progression, but also in homeostasis and regeneration. As the phenotype of endothelial cells (ECs) is continuously regulated by local biomechanical forces, studying endothelial behaviour in altered gravity might contribute to new insights towards angiogenesis modulation. This study aimed at characterizing EC behaviour after hypergravity exposure (more than 1g), with special focus on cytoskeleton architecture and capillary-like structure formation. Herein, human umbilical vein ECs (HUVECs) were cultured under two-dimensional and three-dimensional conditions at 3g and 10g for 4 and 16 h inside the large diameter centrifuge at the European Space Research and Technology Centre (ESTEC) of the European Space Agency. Although no significant tendency regarding cytoskeleton organization was observed for cells exposed to high g's, a slight loss of the perinuclear localization of β-tubulin was observed for cells exposed to 3g with less pronounced peripheral bodies of actin when compared with 1g control cells. Additionally, hypergravity exposure decreased the assembly of HUVECs into capillary-like structures, with a 10g level significantly reducing their organization capacity. In conclusion, short-term hypergravity seems to affect EC phenotype and their angiogenic potential in a time and g-level-dependent manner.

Characterizing atmospheric waves on Venus, Earth, and Mars

Atmospheric Waves Workshop; Noordwijk, Netherlands, 9–10 November 2011 Experts in observations and modeling of atmospheric waves from the Earth and planetary atmospheric science communities came together at a November 2011 workshop held at the European Space Agency's (ESA) European Space Research and Technology Centre ( ESTEC) site in the Netherlands to discuss the nature of waves observed in Venus's atmosphere and their comparison to those on Earth and Mars. ESA's Venus Express (VEx) satellite and ground‐based observers find atmospheric waves at many scales. Migrating solar tides and other planetary‐ scale waves are observed in cloud‐ tracking wind vectors and temperature fields. Mesoscale gravity waves (GWs) can also be seen at a variety of levels from the cloud base up to the thermosphere, evident in imagery and in vertical profiles of temperature, density, and aerosol abundance. This workshop focused particularly on GWs, as their role in the atmospheric circulation is still poorly understood.

PCR-based analysis of microbial communities during the EuroGeoMars campaign at Mars Desert Research Station, Utah

AbstractThe search for evidence of past or present life on Mars will require the detection of markers that indicate the presence of life. Because deoxyribonucleic acid (DNA) is found in all known living organisms, it is considered to be a ‘biosignature’ of life. The main function of DNA is the long-term storage of genetic information, which is passed on from generation to generation as hereditary material. The Polymerase Chain Reaction (PCR) is a revolutionary technique which allows a single fragment or a small number of fragments of a DNA molecule to be amplified millions of times, making it possible to detect minimal traces of DNA. The compactness of the contemporary PCR instruments makes routine sample analysis possible with a minimum amount of laboratory space. Furthermore the technique is effective, robust and straightforward. Our goal was to establish a routine for the detection of DNA from micro-organisms using the PCR technique during the EuroGeoMars simulation campaign. This took place at the Mars Society's Mars Desert Research Station (MDRS) in Utah in February 2009 (organized with the support of the International Lunar Exploration Working Group (ILEWG), NASA Ames and the European Space Research and Technology Centre (ESTEC)). During the MDRS simulation, we showed that it is possible to establish a minimal molecular biology lab in the habitat for the immediate on-site analysis of samples by PCR after sample collection. Soil and water samples were taken at different locations and soil depths. The sample analysis was started immediately after the crew returned to the habitat laboratory. DNA was isolated from micro-organisms and used as a template for PCR analysis of the highly conserved ribosomal DNA to identify representatives of the different groups of micro-organisms (bacteria, archaea and eukarya). The PCR products were visualized by agarose gel electrophoresis and documented by transillumination and digital imaging. The microbial diversity in the collected samples was analysed with respect to sampling depth and the presence or absence of vegetation. For the first time, we have demonstrated that it is possible to perform direct on-site DNA analysis by PCR at MDRS, a simulated planetary habitat in an extreme environment that serves as a model for preparation and optimization of techniques to be used for future Mars exploration.

Interview

Dr Piero Angeletti and Dr Giovanni Toso are technical staff of the European Space Agency (ESA), and are based at the largest of the ESA's sites, the European Space Research and Technology Centre (ESTEC) in The Netherlands. Here they tell us more about their research and their Letter ‘Synthesis of circular and elliptical sparse arrays’ on page 304.

New developments with design and construction of a thermal/vacuum qualified photogrammetric system

In the frame of the development of a photogrammetric system to be used in thermal/vacuum chambers at the European Space Research and Technology Centre (ESTEC) of European Space Agency (ESA) and other sites across Europe, the design of a network using micro-cameras was specified by ESA-ESTEC. A thermal/vacuum qualified photogrammetric system, which is able to work and acquire images in vacuum and at cryo-temperatures, was constructed by ESA-ESTEC Test Centre Division. The current system uses four space qualified one-mega pixel cameras and is able to measure large space structures in vacuum and at temperatures down to −170 ∘C with a global accuracy better than 1 part per 100,000 in object space. Several tests aiming at the qualification of the sensors and system in terms of operation and accuracy have been carried out. Special measures have been developed and special attention has been taken into account specifically for the first application of the photogrammetric system. It is to verify the ESA’s Herschel Telescope Flight Model alignment positioning.

On-the-fly XMM-Newton Spacecraft Data Reduction on the Grid

We present the results of the first prototype of a XMM-Newton pipeline processing task, parallelized at a CCD level, which can be run in a Grid system. By using the Grid Way application and the XMM-Newton Science Archive system, the processing of the XMM-Newton data is distributed across the Virtual Organization (VO) constituted by three different research centres: ESAC (European Space Astronomy Centre), ESTEC (the European Space research and TEchnology Centre) and UCM (Complutense University of Madrid). The proposed application workflow adjusts well to the Grid environment, making use of the massive parallel resources in a flexible and adaptive fashion.

Possible use of Skull melting under microgravity

Skull melting is a special kind of direct inductive heating which allows quasi-crucible-free processing of materials with very high melting points (3000 K and above). Under terrestrial gravity, the temperature gradients essential to the Skull technique cause buoyancy driven convection in the melt, which might interfere with crystal growth. Skull melting could therefore benefit from processing in a microgravity environment. We report on results of a joint project under contract with the European Space Research and Technology Centre (ESTEC), which has evaluated the possible use of Skull melting in microgravity from two main viewpoints: the power efficiency and the expected effects of μg environment on melt convection.

Application of the object-oriented paradigm for scientific experiment monitoring & control

This paper presents a new approach to the monitoring and control of scientific experiments. This new approach is based on an object-oriented environment composed of three elements: (a) A graphical environment that allows the creation of an object-oriented model of the experiment based on objects, attributes and methods. (b) A language for writing procedures to access the model by sending messages in order to operate the experiment. (c) A man-machine interface based on an interactive graphical layer above the object-oriented representation for controlling and monitoring the experiment. This new approach has been prototyped in a project called “Man-Machine Interface Software for Ground User Terminal”, or User Terminal in short. The project is carried out by SPACEBEL Informatique on behalf of the European Space Research and Technology Centre (ESTEC). Although this project has been undertaken for the operation of scientific experiments in space, User Terminal can naturally be used for the monitoring and control of ground based experiments. This article presents the User Terminal system as well as one of the first practical exercises performed in the context of the teleoperation of a liquid science experiment to be shipped into space.

Spaceborne autoranging infrared viewing system for thermal mapping of fluids in a microgravity condition

The European Space Research and Technology Centre (ESTEC) has developed a small, space qualified and TV compatible IR viewing system able to visualize thermal flows in fluids in microgravity. This instrument is a part of the diagnostics of a Spacelab facility, namely the Autonomous Fluid Physics Module (AFPM) flown on the last Spacelab D2 mission (April to May 1993). One of the main objectives of the research is to enable monitoring changes in the surface temperature of a fluid following the application of different stimuli. The only way to achieve this without disturbing the fluid under test is to use nonintrusive infrared measurement techniques. Starting from a basic commercial item, the Agema 870 scanner, ESTEC designed and built a thermal mapping diagnostic system provided with an autoranging capability that allows real-time temperature measurement in the range from 0 to 80°C and with a frame rate of 6 images/s. The geometrical resolution is 70 x 70 pixels in a field of view of 130 x 1 30 mm, which maps out the full temperature distribution of a typical fluid column experiment. An automatic compensation of the background noise at room temperature keeps the minimum resolvable temperature difference (MRTD) figure below 0.2°C. Therefore, the overall accuracy of the system allows one to follow the evolution of the complex phenomena related to the heat convection and mass transport effects at the surface of fluids in a weightlessness environment. The general design of the thermal mapping diagnostic (TMD) system is described and the technical solutions adopted to achieve the scientific goals of the investigation carried out with the AFPM are presented.

Into Space with ESTEC

The European Space Agency rose from the merging of the European Space Research Organisation (ESRO) and the European Space Vehicle Launcher Development Organisation (ELDO). After two-three years of its existence, it is time to review its new structure, functions and achievements, with particular reference to the European Space Research and Technology Centre (ESTEC), ESA's technical centre in Noordwijk, The Netherlands.

THE EUROPEAN SPACE TRIBOLOGY LABORATORY

The European Space Tribology Laboratory (ESTL) is operated for the European Space Research and Technology Centre (ESTEC) (Agence Spatiale Européenne) by the National Centre of Tribology at Risley, Warrington, Lancs. Work carried out here includes the testing of satellites under conditions which reproduce closely those encountered in space, and research on the processes of tribology in extreme vacuum. The following is an updated extract from Industries Atomique et Spatiales (2, 1974) by Dr E. J. Robbins, Manager of ESTL and a Principal Scientific Officer of UKAEA.