Exoplanet atmospheres with EChO: spectral retrievals using EChOSim

We demonstrate the effectiveness of the Exoplanet Characterisation Observatory mission concept for constraining the atmospheric properties of hot and warm gas giants and super Earths. Synthetic primary and secondary transit spectra for a range of planets are passed through EChOSim (Waldmann & Pascale 2014) to obtain the expected level of noise for different observational scenarios; these are then used as inputs for the NEMESIS atmospheric retrieval code and the retrieved atmospheric properties (temperature structure, composition and cloud properties) compared with the known input values, following the method of Barstow et al. (2013a). To correctly retrieve the temperature structure and composition of the atmosphere to within 2 {\sigma}, we find that we require: a single transit or eclipse of a hot Jupiter orbiting a sun-like (G2) star at 35 pc to constrain the terminator and dayside atmospheres; 20 transits or eclipses of a warm Jupiter orbiting a similar star; 10 transits/eclipses of a hot Neptune orbiting an M dwarf at 6 pc; and 30 transits or eclipses of a GJ1214b-like planet.Comment: 13 pages, 15 figures, 1 table. Accepted by Experimental Astronomy. The final publication will shortly be available at Springer via http://dx.doi.org/10.1007/s10686-014-9397-

Enumeration of distinct mechanically stable disk packings in small systems

We create mechanically stable (MS) packings of bidisperse disks using an algorithm in which we successively grow or shrink soft repulsive disks followed by energy minimization until the overlaps are vanishingly small. We focus on small systems because this enables us to enumerate nearly all distinct MS packings. We measure the probability to obtain a MS packing at packing fraction $\phi$ and find several notable results. First, the probability is highly nonuniform. When averaged over narrow packing fraction intervals, the most probable MS packing occurs at the highest $\phi$ and the probability decays exponentially with decreasing $\phi$. Even more striking, within each packing-fraction interval, the probability can vary by many orders of magnitude. By using two different packing-generation protocols, we show that these results are robust and the packing frequencies do not change qualitatively with different protocols.Comment: 4 pages, 3 figures, Conference Proceedings for X International Workshop on Disordered System

Probing Mars’ atmosphere with ExoMars Mars Climate Sounder

The 2016 Mars Trace Gas Mission will carry with it the ExoMars Mars Climate Sounder instrument, a development of the very successful Mars Climate Sounder instrument already in orbit about Mars on NASA's Mars Reconnaissance Orbiter spacecraft. EMCS will continue the monitoring of Mars global temperature/pressure/aerosol field, and will also be able to measure the vertical profile of water vapour across the planet from 0 – 50 km. Key components of EMCS will be provided by Oxford, Reading and Cardiff Universities and the observations will be partly reduced by the instrument team at Oxford. The physical properties retrieved from these observations will be assimilated into Global Circulation Models at Oxford and at The Open University to provide a much clearer picture of the dynamics and transport processes in Mars' atmosphere

Dialogue games for explaining medication choices

SMT solvers can be used efficiently to search for optimal paths across multiple graphs when optimising for certain resources. In the medical context, these graphs can represent treatment plans for chronic conditions where the optimal paths across all plans under consideration are the ones which minimize adverse drug interactions. The SMT solvers, however, work as a black-box model and there is a need to justify the optimal plans in a human-friendly way. We aim to fulfill this need by proposing explanatory dialogue protocols based on computational argumentation to increase the understanding and trust of humans interacting with the system. The protocols provide supporting reasons for nodes in a path and also allow counter reasons for the nodes not in the graph, highlighting any potential adverse interactions during the dialogue.Postprin

High-Energy Proton Testing of Sensitive Electronics for use on Modular Infrared Molecules and Ices Sensor (MIRMIS) Instrument

The Comet Interceptor (CI) mission is ESA\u27s first F class mission, selected in June 2019. This mission consists of three spacecraft: Spacecraft A (main spacecraft), Spacecraft B1 (supplied by the Japanese space agency JAXA), and Spacecraft B2. In this paper, we highlight the Modular Infrared Molecular and Ices Sensor (MIRMIS) instrument, which is integrated into the CI Spacecraft A\u27s scientific payload. In addition to hardware contributions from Finland (VTT Finland) and the UK (University of Oxford), the MIRMIS instrument team includes members from the University of Helsinki and NASA\u27s Goddard Space Flight Centre. MIRMIS covers the spectral range of 0.9 to ~25 μm. This paper presents the preliminary high-proton-energy radiation test results of MIRMIS’ near-infrared detector arraysensitive electronic components. Proton beam testing is performed to estimate Single Event Effects (SEE) on the PCB boards and SEE and Total Non-Ionizing Dose (TNID)/ Displacement Damage (DD) on the detectors. The tests were conducted at the Paul Scherrer Institute (PSI) Proton Irradiation Facility (PIF), Villigen, Switzerland. The levels for the tests were based on the mission requirements for the ESA Comet Interceptor mission: 3 years (at 1 AU- Segment 1) and 2 years (at 0.9 AU- Segment 2). The DD levels from the analysis were equivalent to 1e11 protons/cm2 with an energy of 50 MeV. The electronics are exposed to high-energy protons causing Single Event Effects (SEE) which may induce potentially destructive and non-destructive effects. The test items primarily included the InGaAs image sensors (SCD Cardinal640, standard and low noise), Xilinx Spartan-6 FPGAs (Field Programmable Gate Arrays), and other proximity electronics. The proton energies were varied from 50 to 200 MeV, at fluxes of 106 to 108 particles/cm2/s. No events were observed on the standard Cardinal640 sensor at target fluences between 1.00E+10 to 1.00E+11 particles/cm2. FPGAs did not show any susceptibility to TNID at fluences up to 1.00E+11 (particles/cm2)

The Transit Spectra of Earth and Jupiter

In recent years, a number of observations have been made of the transits of 'Hot Jupiters', such as HD 189733b, which have been modelled to derive atmospheric structure and composition. As measurement techniques improve, the transit spectra of 'Super-Earths' such as GJ 1214b are becoming better constrained, allowing model atmospheres to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets such as the Earth or cold planets like Jupiter, this may become practical in the coming decades and if so, it is of interest to determine what we might infer from such measurements. Here we have constructed atmospheric models of the Solar System planets from 0.4 - 15.5 microns that are consistent with ground-based and satellite observations and from these calculate the primary transit and secondary eclipse spectra (with respect to the Sun and typical M-dwarfs) that would be observed by a 'remote observer', many light years away. From these spectra we test what current retrieval models might infer about their atmospheres and compare these with the 'ground truths' in order to assess: a) the inherent uncertainties in transit spectra observations; b) the relative merits of primary transit and secondary eclipse spectra; and c) the advantages of directly imaged spectra. We find that secondary eclipses would not give sufficient information, but that primary transits give much better determination. We find that a single transit of Jupiter in front of the Sun could potentially be used to determine temperature and stratospheric composition, but for the Earth the mean atmospheric composition could only be determined if it were orbiting an M-dwarf. For both planets we note that direct imaging with sufficient nulling of the light from the parent star provides the best method of determining the atmospheric properties of such planets

Using Apollo Sites and Soils to Compositionally Ground Truth Diviner Lunar Radiometer Observations

Apollo landing sites and returned soils afford us a unique opportunity to "ground truth" Diviner Lunar Radiometer compositional observations, which are the first global, high resolution , thermal infrared measurements of an airless body. The Moon is the most accessible member of the most abundant class of solar system objects, which includes Mercury, asteroids, and icy satellites. And the Apollo samples returned from the Moon are the only extraterrestrial samples with known spatial context. Here we compare Diviner observations of Apollo landing sites and compositional and spectral laboratory measurements of returned Apollo soils. Diviner, onboard NASA's Lunar Reconnaissance Orbiter, has three spectral channels near 8 micron that were designed to characterize the mid-infrared emissivity maximum known as the Christiansen feature (CF), a well-studied indicator of silicate mineralogy. It has been observed that thermal infrared spectra measured in simulated lunar environment (SLE) are significantly altered from spectra measured under terrestrial or martian conditions, with enhanced CF contrast and shifted CF position relative to other spectral features. Therefore only thermal emission experiments conducted in SLE are directly comparable to Diviner data. With known compositions, Apollo landing sites and soils are important calibration points for the Diviner dataset, which includes all six Apollo sites at approximately 200 m spatial resolution. Differences in measured CFs caused by composition and space weathering are apparent in Diviner data. Analyses of Diviner observations and SLE measurements for a range of Apollo soils show good agreement, while comparisons to thermal reflectance measurements under ambient conditions do not agree well, which underscores the need for SLE measurements and validates our measurement technique. Diviner observations of Apollo landing sites are also correlated with geochemical measurements of Apollo soils from the Lunar Sample Compendium. In particular, the correlations between CF and FeO and AI203 are very strong, owing to the dependence on the feldspar-mafic ratio. Our analyses suggest that Diviner data may offer an independent measure of soil iron content from the existing optical and gamma-ray spectrometer datasets

Measurement of the Solar Neutrino Capture Rate by the Russian-American Gallium Solar Neutrino Experiment During One Half of the 22-Year Cycle of Solar Activity

We present the results of measurements of the solar neutrino capture rate in gallium metal by the Russian-American Gallium Experiment SAGE during slightly more than half of a 22-year cycle of solar activity. Combined analysis of the data of 92 runs during the 12-year period January 1990 through December 2001 gives a capture rate of solar neutrinos with energy more than 233 keV of 70.8 +5.3/-5.2 (stat.) +3.7/-3.2 (syst.) SNU. This represents only slightly more than half of the predicted standard solar model rate of 128 SNU. We give the results of new runs beginning in April 1998 and the results of combined analysis of all runs since 1990 during yearly, monthly, and bimonthly periods. Using a simple analysis of the SAGE results combined with those from all other solar neutrino experiments, we estimate the electron neutrino pp flux that reaches the Earth to be (4.6 +/- 1.1) E10/(cm^2-s). Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is approximately (7.7 +/- 1.8) E10/(cm^2-s), in agreement with the standard solar model calculation of (5.95 +/- 0.06) E10/(cm^2-s).Comment: English translation of article submitted to Russian journal Zh. Eksp. Teor. Fiz. (JETP); 12 pages, 5 figures. V2: Added winter-summer difference and 2 reference

The BNO-LNGS joint measurement of the solar neutrino capture rate in 71Ga

We describe a cooperative measurement of the capture rate of solar neutrinos by the reaction 71Ga(\nu_e,e^-)71Ge. Extractions were made from a portion of the gallium target in the Russian-American Gallium Experiment SAGE and the extraction samples were transported to the Gran Sasso laboratory for synthesis and counting at the Gallium Neutrino Observatory GNO. Six extractions of this type were made and the resultant solar neutrino capture rate was 64 ^{+24}_{-22} SNU, which agrees well with the overall result of the gallium experiments. The major purpose of this experiment was to make it possible for SAGE to continue their regular schedule of monthly solar neutrino extractions without interruption while a separate experiment was underway to measure the response of 71Ga to neutrinos from an 37Ar source. As side benefits, this experiment proved the feasibility of long-distance sample transport in ultralow background radiochemical experiments and familiarized each group with the methods and techniques of the other.Comment: 7 pages, no figures; minor additions in version

Compositional Ground Truth of Diviner Lunar Radiometer Observations

The Moon affords us a unique opportunity to "ground truth" thermal infrared (i.e. 3 to 25 micron) observations of an airless body. The Moon is the most accessable member of the most abundant class of solar system bodies, which includes Mercury, astroids, and icy satellites. The Apollo samples returned from the Moon are the only extraterrestrial samples with known spatial context. And the Diviner Lunar Radiometer (Diviner) is the first instrument to globally map the spectral thermal emission of an airless body. Here we compare Diviner observations of Apollo sites to compositional and spectral measurements of Apollo lunar soil samples in simulated lunar environment (SLE)