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 CEAS Space JournalJournal Prestige (SJR): 0.278 Citation Impact (citeScore): 1Number of Followers: 2      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1868-2510 - ISSN (Online) 1868-2502 Published by Springer-Verlag  [2351 journals]
• Concept for a Gossamer solar power array using thin-film photovoltaics
• Abstract: Abstract In recent years, the German Aerospace Center (DLR) developed Gossamer deployment systems in different projects. As power requirements of spacecraft are getting more and more demanding, DLR recently focused on the development of new deployable photovoltaic (PV) technologies that are suitable for generating 10’s of kW per array. Possible space applications that may also require high power supply are missions using electric propulsion such as interplanetary missions, placing of geostationary (GEO) satellites in their orbit or even more future oriented as space tugs or lightweight power generation on extra-terrestrial infrastructures. The paper gives an overview about a feasibility study for flexible solar arrays based on new thin-film photovoltaics. It is expected that the combination of new thin-film PV technologies, e.g., copper indium gallium selenide (CIGS) cells or gallium–arsenide (GaAs) cells, together with Gossamer deployment technologies, could significantly increase the power availability for spacecraft. Based on a requirement, analysis system concepts were evaluated. A focus is on the potential of CIGS PV combined with a two-dimensional deployment of the array and DLR’s coilable carbon fibre-reinforced plastic (CFRP) booms. Therefore, a concept based on crossed booms with a foldable PV membrane is considered as baseline for further developments. The array consists of rectangular PV generators that are interconnected by flexible printed circuit board (PCB) harness. By a double-folding technique, these generators are laid on top of each other in such that the membrane can be extracted from its stowing box during the deployment in a controlled manner. Considering constantly increasing efficiencies of the CIGS PV combined with Gossamer structures, there is clear potential of reaching a very high specific power value exceeding that of conventional PV systems. Furthermore, the CIGS PV appears to be more radiation resistant and has already reached more than 21% efficiency in laboratories. Such efficiencies are expected to be achieved in the near future in a standard manufacturing process. However, flexible, thin-film GaAs cells are also subject of consideration within GoSolAr. With this prospect, DLR’s research has the goal to develop a Gossamer Solar Array (GoSolAr) to exploit the described potential.
PubDate: 2019-09-17

• The challenges of measuring methane from space with a LIDAR
• Abstract: Abstract Remote sensing of methane fluxes has been highlighted as one of the measurement goals of the NASA 2017 Earth Science Decadal Survey. Measuring methane from space and airborne platforms with an active (laser) remote sensing instrument presents several technology and measurement challenges that need to be met in order to provide accurate and precise data. The instrument must be able to make continuous measurements day and night, over all seasons and at all latitudes. It must have a high signal-to-noise ratio and must be relatively immune to biases from aerosol/cloud scattering, spectroscopic and meteorological data uncertainties, and other systematic errors. In this paper, we will discuss the technology challenges, options and tradeoffs to measure methane from space and airborne platforms.
PubDate: 2019-09-14

• Radiometric calibration of the SIMBIO-SYS STereo imaging Channel
• Abstract: Abstract The STereo imaging Channel (STC) is a double wide-angle camera developed to be one of the channels of the SIMBIO-SYS instrument onboard of the ESA BepiColombo mission to Mercury. STC main goal is to map in 3D the whole Mercury surface. The geometric and radiometric responses of the STC Proto Flight model have been characterized on-ground during the calibration campaign. The derived responses will be used to calibrate the STC images that will be acquired in flight. The aim is to determine the functions linking the detected signal in digital number to the radiance of the target surface in physical units. The result of the radiometric calibration consists in the determination of well-defined quantities: (1) the dark current as a function of the integration time and of the detector temperature, settled and controlled to be stable at 268 K; (2) the read out noise, which is associated with the noise signal of the read-out electronic; and (3) the fixed pattern noise, which is generated by the different response of each pixel. Once these quantities are known, the photon response and the photo-response non-uniformity, which represents the variation of the photon responsivity of a pixel in an array, can be derived. The final result of the radiometric calibration is the relation between the radiance of an accurately known and uniform source, and the digital numbers measured by the detector.
PubDate: 2019-09-13

• The TRIPLE/nanoAUV initiative a technology development initiative to
support astrobiological exploration of ocean worlds
• Abstract: Abstract From a scientific point of view, the exploration of oceans on other planets and moons in our solar system is extremely enticing, however, from a technical point of view, it is an almost insurmountable challenge. It is this particular combination of space and ocean-going equipment that makes developing a coherent system such a demanding task. The TRIPLE/nanoAUV Initiative, where the acronym TRIPLE stands for “Technologies for Rapid Ice Penetration and subglacial Lake Exploration”, is intended to specifically address the design and realization of an autonomous underwater vehicle, the nanoAUV, for future space missions that can be operated in conjunction with melting probes for reaching subglacial lakes or ocean waters. Any conceivable technical concept has to first undergo extensive testing in appropriate Earth-analogue environments which at least come close to the actual conditions that are expected on the envisaged space mission in order to provide an indication of the technical feasibility. For the time being Antarctica appears to be the most favorable region for the anticipated test missions including reaching subglacial lakes like the one in the Dome C region although other regions like Devon Ice Cap in Canada will be considered as well. It is not just the basic physical conditions such as a thick ice cover above liquid water/seawater but also the sparsity of microbial life forms that makes it a good Earth-analogue environment [1] as it poses similar challenges to the deployed systems as found on space missions. Just recently, it was discerned that the basic requirements of a planetary mission, melting through the ice and deploying robotic systems into the water body below, are perfectly matching the interest of terrestrial scientific missions. The recent larger breaks off of the Antarctic ice shelf have exposed pristine ocean regions that due to their difficult accessibility necessitate the use of robotic exploration tools. This momentum shall be used to get one step closer to a future planetary mission by evaluating related scientific and technical concepts in Earth-analogue environments.
PubDate: 2019-09-10

• NanoCarb hyperspectral sensor: on performance optimization and analysis
for greenhouse gas monitoring from a constellation of small satellites
• Abstract: Abstract NanoCarb is an innovative Fourier-transform imaging spectrometer dedicated to the measurement of CO2 and CH4. Both its unusual optical principle and sampling strategy allow to reach a compact design, ideal for small satellite constellation as investigated by the European project SCARBO. The NanoCarb performance assessment as well as a proof of concept is required in this framework. We have developed a design strategy to optimize the performances. We demonstrate the potential of the concept through an estimation of the sensitivity, compliant with the space mission target. We also present a preliminary mitigation of the bias induced by water on CO2 and CH4 retrieval, illustrating the efficiency and the flexibility of the NanoCarb partial interferogram sampling technique. The presented design reaches a sub-ppm random error for CO2 and sub-10 ppb random error for CH4, considering 128 km swath and 2 by 2 km2 ground resolution. Design optimization and more systematic performances are discussed.
PubDate: 2019-09-09

• Fast, robust and near-optimal approximation of GTO trajectories and
payload capacities of multistage rockets
• Abstract: Abstract A method for automatically generating approximate trajectories for multistage rockets, launching into a geostationary transfer orbit, is presented. It can either be used to generate an initial guess or to determine the payload capacity of a given launcher. Only the apogee is directly optimized. When the maximum payload of the launcher is used, the perigee will gravitate towards its target value. The method is applicable to configurations consisting of three stages or two stages plus boosters. The trajectory is divided into three steps, one for each stage plus one for all boosters. Five control parameters are used: The first is the constant pitch rate, used during the pitch over maneuver. The other four define the angle of attack rate functions. A declining exponential function is used for $$\dot{\alpha }_2(t)$$ , whereas $$\dot{\alpha }_3(t)$$ is chosen so that $$\alpha _3(t)$$ becomes an inverted parabola. The trajectory algorithm consists of an outer and an inner loop. The outer loop varies the pitch rate to attain the correct apogee. It calls the inner loop, which adjusts the two parameters that define $$\dot{\alpha }_2(t)$$ so that the flight path angle rate at the end of the second step becomes zero. Tests were performed for a model of Ariane 40. Its payload capacity was determined in less than $${30}\hbox { s}$$ and the result matched the one produced by a conventional approach. Moreover, a Monte Carlo simulation, based on the Ariane 40 model, was performed for both applications. The success rate was 94% for the first and 93% for the second case.
PubDate: 2019-09-01

• Micro-pins: the next step in composite–composite and
metal–composite joining
• Abstract: Abstract This study researches a novel advanced joining technique, utilizing metal additive manufacturing, named μPinning. μPins are small pin-like structures manufactured on a metal substrate and used to penetrate and be consolidated inside a fibre-reinforced polymer (FRP) laminate as through-the-thickness reinforcement during curing (Ucsnik et al. in Composite to composite joint with lightweight metal reinforcement for enhanced damage tolerance. ECCM16—16th European Conference on Composite Materials, Seville, Spain, 2014, Parkes et al. in Compos Struct 118:250–256, 2014). Prior studies have shown a significant increase in the load bearing capabilities of the joint [1, 2], as well as greater performance in dynamic and fatigue loads (Graham et al. in Compos Part A 64:11–24, 2014, Chang et al. in Compos Sci Technol 66(13):2163–2176, 2006, Ko et al. in Compos Struct 119:59–66, 2015]. The main objective of this research is to use numerical optimization tool to optimize the shape of a μPin, as studies have shown that the shape of the μPin exhibits a significant role in the mechanical response [1, 2, 5, 7]. After the numerical optimization, experimental testing was performed to validate the assumption of the importance of the μPin shape in the joint loading response. Finally, this study aims to lead to future research on the design of metal inserts in sandwich structures and struts for use in space applications.
PubDate: 2019-09-01

• Influence of transpiration cooling on second-mode instabilities
investigated on hypersonic, conical flows
• Abstract: Abstract In the present study, the influence of active cooling on hypersonic boundary-layer transition at different Mach numbers, from 7 up to 10, is investigated. The analyses are carried out on a $$7^\circ$$ half-angle, blunted cone with different nose radii and various gas injection mass flow rates. In all cases, low mass fluxes, which do not inducing visible shocks in the schlieren images, are applied. As injection gas nitrogen is used. At the considered free stream conditions, second modes are the dominant boundary-layer instabilities, which are consequently the focus of this study. The stability analyses are performed by means of the stability code NOLOT, NOnLOcal Transition analysis, of the German Aerospace Center (DLR). The influence of different mass injections on the frequencies and growth rates of the second modes is analyzed in detail. The effect on the transition onset locations is discussed. The numerical predictions are compared with experimental results. The experimental data referred to in the present study were obtained in the DLR High Enthalpy Shock Tunnel Göttingen.
PubDate: 2019-09-01

• Survey of the operational state of the art in conjunction analysis
• Abstract: Abstract In the last two decades all major space agencies have established processes for operational conjunction analysis (CA) and collision avoidance (COLA). This work highlights the approaches of ESA, DLR, JAXA, NASA, CNES, and CSA. It is found that commercial satellite operators (Inmarsat, Intelsat, SES, and Eutelsat) do not primarily rely on the same sources of data as the major space agencies; however, a common operational process could be identified. Beside comparing the current operational state of the art, the models and methods used by the Combined Space Operations Center (CSpOC) to compute Conjunction Data Messages were studied. The space situational awareness (SSA) community still heavily depends on data provided by CSpOC; however, alternatives are maturing. Last but not least the operational state of the art is compared to theoretical developments of the SSA community. It is shown that while operational tools and processes meet the current needs, the gap is widening with respect to new high-fidelity methods available in literature (e.g., non-Gaussian uncertainty representations). This gap needs to be reduced for the systems to maintain compatibility to future requirements and expected perimeter changes, as for instance a heavily increased number of conjunction messages due to new sensor systems, such as the space fence radar and mega-constellation operations.
PubDate: 2019-09-01

• An early warning system for payloads’ operations in the European
International Space Station (ISS) Columbus module
• Abstract: Abstract Since the Columbus module became part of the ISS in 2008, it provided research opportunities in special experiment facilities for fluid physics (e.g. for crystallization processes, emulsion stability), biology (housing, e.g. small plants and invertebrates) and human research (ageing process, osteoporosis, etc.). In addition, the Columbus Centre Aisle (ambient conditions, i.e. 18–27 °C at 965–1027 hPa) and external platforms (vacuum at − 270 °C) are available for all types of investigations in microgravity. Before an experiment or a payload is implemented and executed, it needs to be analysed if there are any conflicts with other experiments or payloads to be expected. The analyses cover all relevant aspects: mechanical issues, microgravity impact and requirements, data management, power availability, etc. A typical result of the microgravity (µg) analysis is that a µg-sensitive experiment cannot be operated simultaneously with a payload that uses a centrifuge. Results of the analyses are formulated as GuideLines and operational Constraints (GL&Cs). This paper presents different types of analyses including examples and parties involved. Furthermore, the impact of these GL&Cs on the operation community is highlighted. Finally, a new tool for the analyses of all mechanical aspects (using virtual reality) is introduced.
PubDate: 2019-09-01

• Ship tracking results from state-of-the-art space-based AIS receiver
systems for maritime surveillance
• Abstract: Abstract Norway currently operates four satellites with Automatic Identification System (AIS) receivers. The first-generation satellites, AISSat-1 and AISSat-2, are equipped with a two-channel, single-antenna AIS receiver, while NorSat-1 and NorSat-2 are equipped with an improved AIS receiver capable of decoding on all four AIS channels and using the two antennas installed on the NorSat satellites. This paper aims to investigate the ship tracking performance enhancement realised by the technology improvements of antenna diversification, frequency diversification, and advanced algorithms. The ship tracking capability of the NorSat satellites is presented and shown to yield a significant improvement, up to a 20% point increase, over the first AISSat generation ship tracking capability. A further 20% point increase is achieved in select areas using frequency diversity introduced in the AIS system since the development of the AISSat satellites. In addition, NorSat-1 detected 34% more vessels than AISSat-2 over the same timeframe. The contribution to the performance improvement from the incremental improvements in decoding algorithms, antenna diversity, and frequency diversity is indicated in the results. The results indicate that, in the short term, upgrading to the latest algorithms, low noise electronics, and taking advantage of antenna diversity is the greatest performance enhancer. In the medium and long term, the frequency diversity likely yields the greatest performance enhancement.
PubDate: 2019-09-01

• Quasi-impulsive maneuvers to correct mean orbital elements in LEO
• Abstract: Abstract An approach is developed to compute quasi-impulsive maneuvers to steer the orbital elements of a spacecraft to a desired value. Using Gauss variational equations it is possible to define the location along the orbit as well as the magnitude of the maneuver(s) so that specific orbital elements can be changed with little influence on the others. The possibility to include the effect of the perturbations allows an accurate evaluation of the time required to reach the maneuvering location. Including a model of the propulsion system makes the simulation more realistic, if compared with an impulsive maneuver implementation, since a burning arc can replace the instantaneous change of the orbital elements, which is instead associated with the impulsive approach. Simulations have been performed to compare perturbed and unperturbed cases and the results from the comparisons are presented.
PubDate: 2019-09-01

• Sentinel-1 SAR instrument improved flight predictions based on measured
in-orbit data
• Abstract: Abstract The Sentinel-1A SAR mission was launched in April 2014, followed by the Sentinel-1B Spacecraft in April 2016. Since then, several sets of in-orbit data have been evaluated to correlate the thermal model for being able to provide more detailed in-flight predictions. The need for detailed in-flight predictions is justified by the fact that the imaging performance of a SAR instrument depends mainly on the thermal performance of its high dissipative units. Components reaching their temperature limits during operational time define the end of the imaging phase, and thus the timespan during which and how often imaging operations can take place. An STM (Structural/Thermal Model) test correlation is standard throughout all missions, which usually delivers a very reliable model for further in-flight predictions. Nevertheless, this correlation does not give information about thermo-optical property degradation or environmental influences, because the effects in space on the thermally active surfaces are very hard to predict. For this reason, thermal engineers use relatively conservative values for in-flight predictions and End-of-Life thermal performance assessments. This might lead to mission performance limitations which predict a too short feasible imaging time of the Radar instrument. For this reason, the first approach was to evaluate the early acquired in-orbit data and to correlate the thermal model with the thermal configuration at Begin-of-Life to assess the maximum possible high dissipative imaging time possible for the Begin-of-Life situation. Then the flight data over a longer timespan were evaluated to determine potential temperature trends which could be caused by thermo-optical property degradation as well as seasonal-related influences. These two assessments combined, allow a thermal performance prediction for Mission End-of-Life, and thus a reliable determination of potential SAR imaging performance over the full mission time. The paper will present the correlation results of the initially measured in-flight data, the determined long-term in-orbit data over 3 years, and the combination of both assessments including its impact on SAR imaging performance over the full mission.
PubDate: 2019-09-01

• Ballistic and mechanical characteristics of paraffin-based solid fuels
PubDate: 2019-09-01

• Innovative setup for cryogenic mechanical testing of high-strength
metallic alloys
• Abstract: Abstract Mechanical properties of two high-strength metallic alloys, fabricated using additive manufacturing (AM) technology, were characterised down to − 269 °C. A test setup has been developed to accommodate the specific sample geometry and manufacturing conditions for these tests. Tensile, compression, pin-bearing, and shear tests were performed at room temperature, − 73 °C, − 196 °C, and − 269 °C. Test equipment and fixtures were designed and optimized to survive the test loads up to 100 kN at low temperatures. Instrumentation for strain, temperature, and displacement was also carefully chosen to record the specimen behaviour and apply the test requirements. The KRP cryo apparatus provided fast cooling and temperature stability during the entire duration of testing. In this paper, we describe the design of the test apparatus, the challenges in development and some results of test runs.
PubDate: 2019-09-01

• Precise and robust optical beam steering for space optical instrumentation
• Abstract: Abstract We present a novel optical beam steering technique for fiber to free-space to fiber-coupling schemes on optical breadboards, which is based on a glass plate and a pair of glass wedges. Our approach permits much finer adjustments of the beam direction and position when compared to conventional beam steering techniques that use adjusting elements of the same mechanical precision. This results in a much increased precision, accuracy, and stability. Furthermore, the presence of a beam steering element in proximity to the fiber coupler allows a great simplification of the design of this element which is typically considered as the most complex and sensitive element on an optical fiber breadboard. Overall, a beam steering precision of better than $$5\,\upmu$$ rad and $$5\,\upmu$$ m is demonstrated, resulting in a resolution in coupling efficiency of 0.1%. Likewise, we demonstrate a fiber-to-fiber-coupling efficiency of more than 89.8%, with a stability of 0.2% in a stable temperature environment and 2% fluctuations over a temperature range from 10 to 40 °C over a measurement time of 14 h. Finally, we observe no non-reversible change in the coupling efficiency after performing a series of tests over large temperature variations ( $$\varDelta T > 30$$  K). This technique can find direct application in proposed missions for quantum experiments in space (Bongs et al. in STE-QUEST space–time explorer and quantum equivalence principle space test, Technical report STE-QUEST, European Space Agency, 2013; Kaltenbaek et al. in EPJ Quantum Technol 3(1):5, 2016; Carraz et al. in Microgravity Sci Technol 26:139, 2014), e.g., in space-based quantum sensing, where precisely controlled laser light is used to cool and manipulate atoms, or in inter-satellite quantum key distribution.
PubDate: 2019-08-27

• Design, development, and flight testing of the vertical take-off and
landing GNC testbed EAGLE
• Abstract: Abstract Precise landing on planets, moons, and other larger celestial bodies requires powered descent, hovering, and vertical landing. Similarly, recent and future concepts for re-usable launch vehicle (RLVs) also involve a vertical take-off and landing. The development of guidance, navigation, and control (GNC) for this type of vehicles is a challenging task. To support this, a vertical take-off and landing vehicle has been developed for demonstrating the capability of conducting soft landings, smooth ascent, and hovering. The focus was put on a platform for testing new and advanced guidance, navigation, and control (GNC) algorithms that employ a base set of sensors and actuators typically present on such vehicles. It should represent a dynamics similar to a thrust vector controlled planetary lander or RLV, and should allow fast turn-around times as well as rapid prototyping capabilities for testing. In addition, the platform should provide the option for an additional small payload, e.g., enhancing the on-board avionics with different or more precise sensors. The result of this platform development is EAGLE (environment for autonomous GNC landing experiments). Its lift-off mass is about $$30\, \text{kg}$$ and it is powered by a jet engine with a maximum thrust of $$400\, \text{N}$$ .
PubDate: 2019-08-24

• MERLIN: design of an IPDA LIDAR instrument
• Abstract: Abstract The Methane Remote Sensing LIDAR Mission (MERLIN) is a joint French–German cooperation on the development, launch and operation of a climate monitoring satellite, executed by the French Space Agency CNES and the German DLR Space Administration. It is focused on global measurements of the spatial and temporal gradients of atmospheric methane (CH4) with a precision and accuracy sufficient to constrain methane fluxes significantly better than with the current observation network. Airbus Defence and Space GmbH was selected by the German DLR Space Administration as the industrial prime contractor for the mission phase C/D, to build the MERLIN Payload, which is the first realization of such an instrument for space. This presentation will concentrate on the architecture and the optical design of the MERLIN Payload, which ensures reliable, high-performance operation of the bi-static DIAL, consisting of separate transmitter (Tx) and receiver paths (Rx). The MERLIN satellite is a secondary passenger payload on the launcher. As such, the satellite places many constraints on the instrument, pertaining to the power, mass and volume allowable. The available resources force the MERLIN instrument to have passive thermal control while necessitating a very compact design due to the demanding envelope constraints. This creates a large operational temperature range with thermal gradients on the structure, requiring an extremely robust optical design in a compact envelope. The robust optical design, for the Rx and Tx paths, employs several passive measures and an active pointing control for Rx and Tx co-alignment. Further details of the instrument development status during the ongoing phase C will be shown by an overview of the current hardware and design status of the major subsystems.
PubDate: 2019-08-23

• The absolute frequency reference unit for the spaceborne methane-sensing
lidar mission MERLIN
• Abstract: Abstract Lidar systems have become an important technology in a variety of industrial and scientific applications. For terrestrial applications, such systems have been developed over the last decade and are commercially available. In space, this technology does not have a comparable maturity level and is still far from being a standard technology. In this paper, we present the operating principle, the design, and performance of the spaceborne absolute frequency reference used in the instrument of the French–German methane remote-sensing lidar mission, MERLIN. The MERLIN instrument operates on a methane absorption feature at 1645.55 nm. To achieve the accuracy goal for the column-integrated methane concentration of 3 ppb, absolute frequency accuracy levels in the low MHz range are required. The absolute frequency reference unit provides the stabilized seed lasers for the high-power laser sources at the required wavelengths and measures the absolute frequency of the outgoing laser pulses by means of a wavemeter. The focus of this paper is on the implementation of the absolute frequency referencing and the obtained frequency stability and accuracy.
PubDate: 2019-08-19

• The BepiColombo Laser Altimeter (BELA): a post-launch summary
• Abstract: Abstract We provide a brief description of the BepiColombo Laser Altimeter experiment for the joint ESA-JAXA mission to Mercury, BepiColombo. The text describes the main elements of the instrument and discusses several of the problems encountered during the instrument development. The actions taken to mitigate the issues are also described and the resulting performance of the instrument as determined by combining ground test data with models of Mercury and the spacecraft orbit is presented. The instrument has met the requirements set in 2005 and should provide a solid data set for the global study of the topography and internal structure of Mercury.
PubDate: 2019-08-13

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