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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  [2574 journals]
• Design of converging-diverging nozzles with constant-radius centerbody
• Abstract: Several flow phenomena, such as recirculating wake flows or noise generation, occur in aerodynamic configurations with backward facing steps. In this context, subsonic nozzles with constant-radius centerbodies exist, which enable fundamental research of these phenomena for $$M < 1$$. For the supersonic regime, however, the existing database and knowledge are limited. Therefore, this work presents a design approach for a converging-diverging nozzle with constant-radius centerbody. For the nozzle throat, Sauer’s method is modified to include a centerbody. The method of characteristics is used for the subsequent supersonic portion. Comparing the analytical calculations to numerical simulations results in very good agreement and therefore underlines the feasibility of the chosen approach. Viscosity reduced the Mach number on the exit plane by 1.0–1.2% and therefore had little influence.
PubDate: 2019-11-15

• Novel gratings for astronomical observation
• Abstract: The choice of transmission grating can facilitate downsizing of a spectrograph and make it possible to achieve a perfect Littrow configuration. We are developing transmission gratings for next-generation instruments for the 8.2 m Subaru Telescope, the Thirty Meter Telescope (TMT), and other ground-based and space-borne telescopes. These include, a volume binary grating developed for an echelle grism (direct vision grating) for the Subaru Multi-Object InfraRed Camera and Spectrograph (MOIRCS); a reflector facet transmission (RFT) grating, a surface relief grating with sawtooth-shaped ridges of an acute vertex angle, expected to be deployed for the TMT Wide Field Optical Spectrograph (WFOS), and a hybrid grism for use as a medium-dispersion grism in MOIRCS, developed as a prototype of RFT grating. We describe the simulation results, fabrication methods, and experimental results of these prototype transmission gratings in this article.
PubDate: 2019-11-14

• Space Lidar and Space Optics
• PubDate: 2019-11-13

• Detection efficiency of microchannel plates to penetrating radiation in
space
• Abstract: Space-based instruments for detection of photons, plasma, and energetic neutral atom imaging include electron multiplier detectors that are subject to increased transient noise, long-term degradation, and even potential failure due to the substantial fluxes of high-energy particles that penetrate the instrument in the space environment. The most commonly used electron multiplier detectors are multi-channel plates (MCP). These detectors are sensitive not only to the incident energetic charged particles themselves but also to the final end-product energy deposited by energetic electrons, ions, and X-rays/gammas. The resulting radiation-induced background noise can potentially contaminate the science signal. This issue constitutes undoubtedly one of the main challenges together with the radiation hardness of the electronics for particle instruments onboard future missions to Jupiter like the European Space Agency (ESA) Jupiter ICy moon Explorer (JUICE), and requires dedicated and innovative radiation mitigation techniques (e.g., multiple coincidence, anti-coincidence) far beyond the simple passive shielding techniques commonly used to protect electronics and other subsystems against total ionizing dose (TID). The accurate response (i.e., efficiency) of MCP detectors against high-energy particles is, however, not well known, with limited estimates available in the literature. This makes it complicated in particular to reliably predict the signal–noise ratio (SNR) of the instrument, and, hence, ensure that the instrument will return useful scientific data when operated in the Jovian magnetosphere. We describe and report in the present paper the results of an experiment in which we measured the response of Photonis MCP detectors to 300–1500 keV electrons and 500 keV photons (gamma rays) using a Van de Graff electron gun available at ONERA, Toulouse, France. The efficiency of the tested MCP for high-energy electrons is about 20–30% below 100 keV and is reduced to 10% for electron energies greater than 100 keV. The efficiency of the tested MCP for the gamma radiation of 500 keV energy is approximately 0.1%.
PubDate: 2019-10-30

• ATLID, ESA atmospheric backscatter LIDAR for the ESA EarthCARE mission
• Abstract: The ATmospheric LIDAR (Light Detection and Ranging), ATLID, is part of the payload of the Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission, the sixth Earth Explorer Mission of the European Space Agency (ESA) Living Planet Programme (http://esamultimedia.esa.int/docs/SP_1279_1_EarthCARE.pdf). The EarthCARE payload consists of four instruments that will, in a synergetic manner, retrieve vertical profiles of clouds and aerosols, and the characteristics of the radiative and micro-physical properties, to determine flux gradients within the atmosphere and top of atmosphere radiance and flux. ATLID’s task is to provide vertical profiles of optically thin cloud and aerosol layers, as well as the altitude of cloud boundaries. With that purpose ATLID emits < 35 ns duration laser pulses with 40 mJ energy in the UV, at a repetition rate of 51 Hz, while pointing in a near nadir direction along track of the satellite trajectory. The backscatter signal is collected by a 620 mm aperture telescope and is then filtered and redirected through the optics of the instrument focal plane assembly, in such a way that the atmospheric Mie and Rayleigh scattering contributions are separated and independently measured. After the manufacturing, qualification and delivery of all ATLID units, the optical and electrical integration has been conducted in parallel to assemble the Optical Flight Model (OFM) and the Electrical Flight Model (EFM). These two models, precursor to the instrument integration, allowed the early execution of the first performance and functional tests. Following these initial verification activities, and with the latest integration of the flight laser cooling system, the instrument assembly approaches its final flight configuration, paving the way for the ambient performance and environmental test campaigns at full instrument level.
PubDate: 2019-10-29

• Hypersonic transatmospheric and exoatmospheric vehicle design using the
SUAVE tool
• Abstract: This work reports the introduction of a set of low-fidelity aerodynamic and propulsion models to the preliminary vehicle design suite SUAVE. This enables the capability to predict transatmospheric and exoatmospheric hypersonic flight performance. Verification and validation for the different subsystem modules have been carried out against existing data, namely regarding the propulsion (ramjet, scramjet, LOX/LH2 rocket, combined-cycle engines) and aerothermodynamic (reentry) subcomponents. Two sample test-cases, based on the vehicular properties of the SR-72 vehicle (size and wing area) have been analyzed. A flight range of about 10,000 km for a flight time between 1 h (exoatmospheric flight) and 2h30 (transatmospheric flight) has been determined for a set of theoretical reasonable efficiencies for the subcomponents (chiefly propulsion). The obtained results provide a contribution to hypersonic vehicle development roadmaps, proposing two credible mission profiles (trans- and exoatmospheric) and highlighting the key role of propulsion technology development for the advancement of the state-of-the-art.
PubDate: 2019-10-25

• The Ganymede laser altimeter (GALA): key objectives, instrument design,
and performance
• Abstract: The Ganymede Laser Altimeter (GALA) is one of the ten scientific instruments selected for the Jupiter Icy Moons Explorer (JUICE) mission currently implemented under responsibility of the European Space Agency (ESA). JUICE is scheduled for launch in mid 2022; arrival at Jupiter will be by end of 2029 with the nominal science mission—including close flybys at Ganymede, Europa, and Callisto and a Ganymede orbit phase—ending by mid 2033. GALA’s main objective is to obtain topographic data of the icy satellites of Jupiter: Europa, Ganymede, and Callisto. By measuring the diurnal tidal deformation of Ganymede, which crucially depends on the decoupling of the surface ice layer from the deep interior by a liquid water ocean, GALA will obtain evidence for (or against) a subsurface ocean in a 500 km orbit around the satellite and will provide constraints on Ganymede’s ice shell thickness. In combination with other instruments, it will characterize the morphology of surface units on Ganymede, Europa, and Callisto providing not only topography but also surface roughness and albedo (at 1064 nm) measurements. GALA is a single-beam laser altimeter operating with up to 50 Hz (nominal 30 Hz) shot frequency at a wavelength of 1064 nm and pulse lengths of $$5.5\pm 2.5$$ ns using a Nd:YAG laser. The return pulse is detected by an Avalanche Photo Diode (APD) with 100 MHz bandwidth and is digitized at a sampling rate of 200 MHz providing range measurements with a subsample resolution of 0.1 m and surface roughness measurements from pulse-shape analysis on the scale of the footprint size of about 50 m at 500 km altitude. The instrument is developed in collaboration of institutes and industry from Germany, Japan, Switzerland, and Spain.
PubDate: 2019-10-21

• Latest modification of the deployable space reflector structure with
V-folding bars
• Abstract: In this paper, a new modification of the mechanical load-bearing ring structure is considered. It is shown that due to the appropriate changes made to the ring, its structure possesses obvious advantages as compared with the previously proposed variant. The projecting tips of the struts to which the central flexible shaping system is attached are replaced by paired levers with torsion springs of new design, which guarantee the smooth deployment of the ring and keep the cables in permanently tensioned condition. In the new modification, the central flexible shaping system is directly attached to the upper and lower hoops of the ring, thereby preventing the bending of struts when the reflector is completely deployed. The new multi-stage deployment scheme of the structure considered in the paper operates without synchronization mechanisms—the upper and lower kinematic chains get deployed not simultaneously as in the previous ring variant but in alternating order. The validity of design computations is confirmed by the FEM mathematical models for which deformations of structural elements, displacement of nodes, and eigenfrequency values are determined. The optimization of structural elements makes it possible to design the mechanical characteristics and strength margin of the ring with a minimal number of elements and minimal cross-sectional values, which simplifies the ring structure on the whole, and reduces its weight.
PubDate: 2019-09-27

• Damping of piezoelectric space instruments: application to an active
optics deformable mirror
• Abstract: This paper presents the shunt damping of a unimorph piezoelectric mirror intended to be used as an active secondary corrector in future space telescopes. We propose to take advantage of the actuation capability of the piezoelectric mirror, to increase its natural damping during the critical launch phase of the spacecraft. The piezoelectric actuators, intended to be used for active optics, are shunted on a passive resistive and inductive RL circuit during the launch operation. The proposed concept is verified numerically and experimentally on a piezoelectric deformable mirror prototype, developed on behalf of the European Space Agency. We show that the shunt damping significantly reduces the response of the most critical mode of the mirror (− 23 dB) as well as the stress in the mirror when subjected to a typical vibro-acoustic launch load. This reduces the risk of damaging the mirror during the delicate launch phase, without increasing the complexity of the design.
PubDate: 2019-09-25

• Correction to: The TRIPLE/nanoAUV initiative a technology development
initiative to support astrobiological exploration of ocean worlds
• Abstract: The article “The TRIPLE/nanoAUV initiative a technology development initiative to support astrobiological exploration of ocean worlds”, written by Christoph Waldmann and Oliver Funke, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 10 September 2019 with open access.
PubDate: 2019-09-24

• Misalignment estimation for active telescopes
• Abstract: The estimation of the misalignment of an active telescope, from aberrations measured in its focal plane, is a tomographic issue. MMSE-based estimation is successfully used in optical tomography issues, like multiconjugate adaptive optics, where the problem is linear, and the phase perturbation spectrum rapidly decreasing. The implementation of MMSE developed in the case of multiconjugate adaptive optics has been applied to the alignment of active telescopes, although the forward problem is not linear, and the aberration spectrum different. Its performance is characterized by numerical modeling in the case of a TMA type large-field imaging space telescope, and compared to the classical Least-Square approach. The MMSE estimation brings a significant gain in terms of robustness and accuracy.
PubDate: 2019-09-20

• Simulation of the electrostatic charging of the MetOp-SG satellites in the
polar auroral zone
• Abstract: The ability to withstand the harsh space environment is one of the key challenges in the design and construction of satellites. One of these special characteristics of space is the plasma environment encountered in orbit. In this paper, the system-level charging analysis and simulations for the METOP-SG satellites are presented. The METOP-SG satellites will be launched into a sun-synchronous low Earth orbit (LEO) with an altitude of 835 km. In this orbit, the local plasma parameters in the so-called auroral zone close to the poles can lead to critical charging of the satellites [1]. The simulations are performed using a three-dimensional satellite model, where the main elements and surfaces are included. The tool for the simulations is the spacecraft plasma interaction software (SPIS) which has been developed under ESA contract [2]. The calculated surface potentials on the satellite are critically reviewed, the possibility for electrostatic discharges (ESD) is analysed, and protective measures for the minimization of the risks to the satellite mission are discussed.
PubDate: 2019-09-20

• Concept for a Gossamer solar power array using thin-film photovoltaics
• 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: 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: 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: 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: 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
• 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: 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: 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

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