Plasma diagnostics and simulation for the SMART-1 mission

SMART-1 is a technology demonstrator for using primary electric propulsion on interplanetary spacecraft. Hence, studying of the interaction of the plasma emitted by the thruster with the environment and the spacecraft is one of the top priorities during the mission. Two experiments (Electronic propulsion diagnostic package and Spacecraft potential, electron and dust experiment) are available to measure the electron densities and temperatures as well as wave electric fields during the operation of the electric propulsion thruster. Additionally, a retarding potential analyser, a quartz microbalance and a solar-cell sample will analyse data from slow charge-exchange ions which are a potential contamination source. ESTEC is developing a 3D particle-in-cell model in order to study the spacecraft/environment interactions on SMART-1 and interpret the measurements. In the present paper, we will review the contamination effects associated with electric propulsion and how the plasma sensors cover them. We further present preliminary results from the numerical simulation and show how the flight data will be used to validate the modelling code. A successful validation of the simulation will support future interplanetary and commercial missions featuring electric propulsion to reduce the risk of contamination and interference with on board instruments.     

The D-CIXS X-ray spectrometer on the SMART-1 mission to the Moon—First results

The SMART-1 mission has recently arrived at the Moon. Its payload includes D-CIXS, a compact X-ray spectrometer. SMART-1 is a technology evaluation mission, and D-CIXS is the first of a new generation of planetary X-ray spectrometers. Novel technologies enable new capabilities for measuring the fluorescent yield of a planetary surface or atmosphere which is illuminated by solar X-rays. During the extended SMART-1 cruise phase, observations of the Earth showed strong argon emission, providing a good source for calibration and demonstrating the potential of the technique. At the Moon, our initial observations over Mare Crisium show a first unambiguous remote sensing of calcium in the lunar regolith. Data obtained are broadly consistent with current understanding of mare and highland composition. Ground truth is provided by the returned Luna 20 and 24 sample sets.     

Scientific rationale for the D-CIXS X-ray spectrometer on board ESA's SMART-1 mission to the Moon

The D-CIXS X-ray spectrometer on ESA's SMART-1 mission will provide the first global coverage of the lunar surface in X-rays, providing absolute measurements of elemental abundances. The instrument will be able to detect elemental Fe, Mg, Al and Si under normal solar conditions and several other elements during solar flare events. These data will allow for advances in several areas of lunar science, including an improved estimate of the bulk composition of the Moon, detailed observations of the lateral and vertical nature of the crust, chemical observations of the maria, investigations into the lunar regolith, and mapping of potential lunar resources. In combination with information to be obtained by the other instruments on SMART-1 and the data already provided by the Clementine and Lunar Prospector missions, this information will allow for a more detailed look at some of the fundamental questions that remain regarding the origin and evolution of the Moon.     

The SMART-1 lunar impact

The SMART-1 spacecraft impacted the Moon on 3rd September 2006 at a speed of 2 km s⁻¹ and at a very shallow angle of incidence (∼1°). The resulting impact crater is too small to be viewed from the Earth; accordingly, the general crater size and shape have been determined here by laboratory impact experiments at the same speed and angle of incidence combined with extrapolating to the correct size scale to match the SMART-1 impact. This predicts a highly asymmetric crater approximately 5.5-26 m long, 1.9-9 m wide, 0.23-1.5 m deep and 0.71-6.9 m³ volume. Some of the excavated mass will have gone into crater rim walls, but 0.64-6.3 m³ would have been ejecta on ballistic trajectories corresponding to a cloud of 2200-21,800 kg of lunar material moving away from the impact site. The shallow Messier crater on the Moon is similarly asymmetric and is usually taken as arising from a highly oblique impact. The light flash from the impact and the associated ejecta plume were observed from Earth, but the flash magnitude was not obtained, so it is not possible to obtain the luminous efficiency of the impact event.     

The D-CIXS X-ray mapping spectrometer on SMART-1

The D-CIXS Compact X-ray Spectrometer will provide high quality spectroscopic mapping of the Moon, the primary science target of the ESA SMART-1 mission. D-CIXS consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy. It will also carry a solar monitor, to provide the direct calibration needed to produce a global map of absolute lunar elemental abundances, the first time this has been done. Thus it will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, by exploiting two new technologies, swept charge devices and micro-structure collimators. The new technology does not require cold running, with its associated overheads to the spacecraft. At the same time it will demonstrate a radically novel approach to building a type of instrument essential for the BepiColombo mission and potential future planetary science targets.     

Overview and current status of the VSOP mission

An overview and status report of the VLBI Space Observatory Programme is presented.     

Scientific objectives and selection of targets for the SMART-1 Infrared Spectrometer (SIR)

The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future.     

The SMART-1 AMIE experiment: implication to the lunar opposition effect

The lunar surface reveals a sharp opposition effect, which is to be explained by the shadowing and coherent backscattering mechanisms. Generalizing the radiative transfer theory via Monte Carlo methods, we are carrying out studies of backscattering in regolith-like scattering media. We have also started systematic laboratory measurements of structural simulators of lunar regolith. The SMART-1 AMIE and D-CIXS/XSM experiments provide us a unique opportunity for a simultaneous multiwavelength study of the lunar regolith close to opposition, since the SMART-1 spacecraft will pass over several different types of lunar surface at zero phase angles. Results of our theoretical and laboratory investigations can be used as a basis to interpret the SMART-1 AMIE and D-CIXS/XSM experiments. In particular, it seems to be possible to estimate regional variations of regolith particle volume fraction and their size. A short review of observational, experimental and theoretical works is also presented here.     

Photometric anomalies of the lunar surface studied with SMART-1 AMIE data

We present new results from the mapping of lunar photometric function parameters using images acquired by the spacecraft SMART-1 (European Space Agency). The source data for selected lunar areas imaged by the AMIE camera of SMART-1 and the data processing are described. We interpret the behavior of photometric function in terms of lunar regolith properties. Our study reveals photometric anomalies on both small (sub-kilometer) and large (tens of kilometers) scales. We found the regolith mesoscale roughness of lunar swirls to be similar in Mare Marginis, Mare Ingenii, and the surrounding terrains. Unique photometric properties related to peculiarities of the millimeter-scale regolith structure for the Reiner Gamma swirl are confirmed. We identified several impact craters of subkilometer sizes as the source of photometric anomalies created by an increase in mesoscale roughness within the proximal crater ejecta zones. The extended ray systems reveal differences in the photometric properties between proximal and distant ejecta blankets. Basaltic lava flows within Mare Imbrium and Oceanus Procellarum indicate higher regolith porosity for the redder soils due to differences in the chemical composition of lavas.     

The SMART-1 Mission: Photometric Studies of the Moon with the AMIE Camera

We describe the future SMART-1 European Space Mission whose objective is to study the lunar surface from a polar lunar orbit. In particular, it is anticipated that selected regions of the Moon will be photographed using the AMIE camera with a mean spatial resolution of about 100 m in three spectral channels (0.75, 0.92, and 0.96 m) over a wide range of phase angles. Since these spectral channels and the AMIE resolution are close to those of the UVVIS camera onboard the Clementine spacecraft, the simultaneous processing of SMART-1 and Clementine data can be planned, for example, to obtain phase-ratio images. These images carry information on the structural features of the lunar surface. In particular, UVVIS/Clementine data revealed a photometric anomaly at the Apollo-15 landing site associated with the blowing of the lunar regolith by the lander engine. Anomalies were found in the ejection zones of several fresh craters.     

Design and on-orbit status of the trigger system for the DAMPE mission

DArk Matter Particle Explorer(DAMPE), the first Chinese astronomical satellite, was successfully launched at the Jiuquan Satellite Launch Center on 2015 Dec. 17. DAMPE consists of four subdetectors: Plastic Scintillator array Detector(PSD), Silicon-Tungsten tracKer-converter(STK), Bismuth Germanium Oxide(BGO) imaging calorimeter and NeUtron Detector(NUD). The global hardware trigger signal, which is generated by hits from the BGO calorimeter and the trigger logic board in the data acquisition system(DAQ), is responsible for event selection and DAQ synchronization of DAMPE. On orbit,to improve the detection efficiency, different trigger logics are used for event selection in different regions of latitude. The DAMPE trigger system compresses the average on-orbit trigger rate to 60 Hz and reduces science data mass to less than 13 GB per day to meet the requirement for the satellite's data link. The whole trigger system has run stably up to now, ensuring excellent on-orbit operation of DAMPE.     

The advanced Moon micro-imager experiment (AMIE) on SMART-1: Scientific goals and expected results

The advanced Moon micro-imager experiment (AMIE) is the imaging system on board ESA mission to the Moon SMART-1; it makes use of a miniaturised detector and micro-processor electronics developed by SPACE X in the frame of the ESA technical programme. The AMIE micro-imager will provide high resolution CCD images of selected lunar areas and it will perform colour imaging through three filters at 750, 915 and 960 nm with a maximum resolution of 46 m/pixel at the perilune of 500 km. Specific scientific objectives will include (1) imaging of high latitude regions in the southern hemisphere, in particular the South Pole Aitken basin (SPA) and the permanently shadowed regions close to the South Pole, (2) determination of the photometric properties of the lunar surface from observations at different phase angles (physical properties of the regolith), (3) multi-band imaging for constraining the chemical and mineral composition of the surface, (4) detection and characterisation of lunar non-mare volcanic units, (5) study of lithological variations from impact craters and implications for crustal heterogeneity. The AMIE micro-imager will also support a Laser-link experiment to Earth, an On Board Autonomous Navigation investigation and a Lunar libration experiment coordinated with radio science measurements.     

The THESEUS space mission: science goals,requirements and mission concept

Experimental Astronomy - THESEUS, one of the two space mission concepts being studied by ESA as candidates for next M5 mission within its Comsic Vision programme, aims at fully exploiting Gamma-Ray...     

Asteroids 1 ceres and 4 vesta: Objects of the Dawn space mission

The Dawn spacecraft of the NASA space mission to asteroids 1 Ceres and 4 Vesta was launched in September 2007. The choice of these two asteroids is deeply grounded: they are the largest and most massive objects of the main belt that are completely different in material composition, evolution history, and internal structure. Recently, the results of observations and numerical modeling have shown their amazing uniqueness: they both have experienced the complex process of thermal evolution and differentiation of their internal mineral resources, but have a completely different internal structure. Being the largest bodies, have they managed to resist the process of collisional evolution in the asteroid belt and have survived in their “primitive form.” Because of this, their study is very important from the point of view of cosmogonic problems regarding the asteroid belt and the Solar System as a whole. The present paper shortly reviews the recent progress in the study of Ceres and Vesta achieved due to observations performed on the Earth (including the polarimetric observations made by the authors) and from the Hubble Space Telescope (HST) before the long-term orbital investigations performed by the Dawn spacecraft.     

STE-QUEST mission and system design

STE-QUEST is a fundamental science mission which is considered for launch within the Cosmic Vision programme of the European Space Agency (ESA). Its main scientific objectives relate to probing various aspects of Einstein’s theory of general relativity by measuring the gravitational red-shift of the earth, the moon and the sun as well as testing the weak equivalence principle to unprecedented accuracy. In order to perform the measurements, the system features a spacecraft equipped with two complex instruments, an atomic clock and an atom interferometer, a ground-segment encompassing several ground-terminals collocated with the best available ground atomic clocks, and clock comparison between space and ground via microwave and optical links. The baseline orbit is highly eccentric and exhibits strong variations of incident solar flux, which poses challenges for thermal and power subsystems in addition to the difficulties encountered by precise-orbit-determination at high altitudes. The mission assessment and definition phase (Phase-A) has recently been completed and this paper gives a concise overview over some system level results.     

TandEM: Titan and Enceladus mission

TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015–2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini–Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini–Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfière) and possibly several landing probes to be delivered through the atmosphere.     

Ultraviolet solar irradiance measurement from 200 to 358 nm during spacelab 1 mission

The paper presents the results obtained from the UV-spectrometer of the Solar Spectrum Experiment during the Spacelab 1 mission in December 1983. The irradiance data concern 492 passbands, which are located between 200 and 358 nm at almost equidistant wavelengths separated by about 0.3 nm. The passbands have a well-defined, bell-shaped profile with a full width at half maximum of about 1.3 nm. The data, which have an error budget between 4 and 5%, agree closely with the spectral distributions observed by Heath (1980) and Mentall et al. (1981) and confirm that the solar irradiance and the fluxes of Sun-like stars show about the same spectral distribution down to at least 240 nm.     

The remarkable surface homogeneity of the Dawn mission target (1) Ceres

Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While Ceres’ visible and near-infrared disk-integrated spectra have been well characterized, little has been done about quantifying spectral variations over the surface. Any spectral variation would give us insights on the geographical variation of the composition and/or the surface age. The only work so far was that of Rivkin and Volquardsen ([2010], Icarus 206, 327) who reported rotationally-resolved spectroscopic (disk-integrated) observations in the 2.2–4.0 μm range; their observations showed evidence for a relatively uniform surface.Here, we report disk-resolved observations of Ceres with SINFONI (ESO VLT) in the 1.17–1.32 μm and 1.45–2.35 μm wavelength ranges. The observations were made under excellent seeing conditions (0.6″), allowing us to reach a spatial resolution of ～75 km on Ceres’ surface. We do not find any spectral variation above a 3% level, suggesting a homogeneous surface at our spatial resolution. Slight variations (about 2%) of the spectral slope are detected, geographically correlated with the albedo markings reported from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al. [2006], Icarus 182, 143; Carry et al. [2008], Astron. Astrophys. 478, 235). Given the lack of constraints on the surface composition of Ceres, however, we cannot assert the causes of these variations.     

The Planck Surveyor mission and gravitational lenses

An extremely sensitive all-sky survey will be carried out in the millimetre/submillimetre waveband by the forthcoming ESA mission Planck Surveyor . The main scientific goal of the mission is to make very accurate measurements of the spatial power spectrum of primordial anisotropies in the cosmic microwave background radiation; however, hundreds of thousands of distant dusty galaxies and quasars will also be detected. These sources are much more likely to be gravitationally lensed by intervening galaxies compared with sources discovered in surveys in other wavebands. Here the number of lenses expected in the survey is estimated, and techniques for discriminating between lensed and unlensed sources are discussed. A practical strategy for this discrimination is presented, based on exploiting the remarkable sensitivity and resolving power of large ground-based millimetre/submillimetre-wave interferometer arrays. More than a thousand gravitational lenses could be detected: a sample that would be an extremely valuable resource in observational cosmology.