Structure and NIR feature of QCC: a laboratory analog of carbon dust.

We have produced thin films of quenched carbonaceous composite (QCC) by hydrocarbon plasma deposition. The effect of thermal annealing on QCC has been investigated to understand how QCC, as a laboratory analog of carbon dust, is transformed in the warm environment around evolved stars. Spectroscopic measurements have indicated that, by heating, the proportion of aromatic sp2 CH bonds increases relative to sp3 CH bonds. Carbon onion-like spherules of approximately 10 nm in diameter are found with electron microscopic images after "graphitization" of thermal annealing.     

The Magnetospheric Multiscale Magnetometers

The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate magnetometers were developed, avoiding single-point failures. The magnetometers were dubbed the digital fluxgate (DFG), which uses an ASIC implementation and was supplied by the Space Research Institute of the Austrian Academy of Sciences and the analogue magnetometer (AFG) with a more traditional circuit board design supplied by the University of California, Los Angeles. A stringent magnetic cleanliness program was executed under the supervision of the Johns Hopkins University’s Applied Physics Laboratory. To achieve mission objectives, the calibration determined on the ground will be refined in space to ensure all eight magnetometers are precisely inter-calibrated. Near real-time data plays a key role in the transmission of high-resolution observations stored on board so rapid processing of the low-resolution data is required. This article describes these instruments, the magnetic cleanliness program, and the instrument pre-launch calibrations, the planned in-flight calibration program, and the information flow that provides the data on the rapid time scale needed for mission success.     

IMF Direction Derived from Cycloid-Like Ion Distributions Observed by Mars Express

Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser (IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF is relatively uniform on a scale larger than the proton gyroradius. During bow shock outbound crossings, MEX often observed cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most likely newly ionized hydrogen atoms, which are picked up by the solar wind.     

Trace — The transition region and coronal explorer

TRACE is a single-instrument solar mission that will be put into a Sunsynchronous polar orbit and will obtain continuous solar observations for about 8 months per year. It will collect images of solar plasmas at temperatures from 10⁴ to 10⁷ K, with 1-arcsec spatial resolution and excellent temporal resolution and continuity. With such data, we expect to gain a new understanding of many solar and stellar problems ranging from coronal heating to impulsive magnetohydrodynamic phenomena.     

Pop-up threat models for persistent area denial

Pop-up threats usually appear or disappear randomly in a battle field. If the next pop-up threat locations could be predicted it would assist a search or attack team, such as in a persistent area denial (PAD) mission, in getting a team of unmanned air vehicles (UAVs) to the threats sooner. We present a Markov model for predicting pop-up ground threats in military operations. We first introduce a general Markov chain of order n to capture the dependence of the appearance of pop-up threats at previous locations of the pop-up threats over time. We then present an adaptive approach to estimate the stationary transition probabilities of the nth order Markov models. To choose the order of the Markov chain model for a specific application, we suggest using hypothesis tests from statistical inference on historical data of pop-up threat locations. Anticipating intelligent responses from an adversary, which might change its pop-up threat deployment strategy upon observing UAV movements, we present adaptive Markov chain models using a moving horizon approach to estimate possibly abrupt changes in transition probabilities. We combine predicted and actual pop-up target locations to develop efficient cooperative strategies for networked UAVs. A theoretical analysis and simulation results are presented to evaluate the Markov model used for predicting pop-up threats. These results demonstrate the effectiveness of cooperative strategies using the combined information of threats and predicted threats in improving overall mission performance.     

In-space, chemically rigidizing structures: Is cure through hot gases feasible?

Chemical rigidization of expandable structures in the space environment for practical reasons requires initiation temperatures upwards of some 370 K. This leads to relatively restrictive requirements for the thermal design of the structure and/or for its thermal conditioning through attitude control. It has been repeatedly suggested to circumvent these obstacles by curing such objects through the use of internal heat sources (hot-gas generator, heaters). This note shows that all such approaches are unfeasible and that, therefore, recourse to thermal conditioning by the Sun is unavoidable.     

Optical oxygen sensor instrumentation based on the detection of luminescence lifetime.

Optical oxygen sensors are mainly based on the principle of luminescence quenching. In contrast to arready existing intensity-based systems, the measurement of the luminescence lifetime provides certain advantages, such as insensitivity to photobleaching or leaching of the dye, or changes in the intensity of excitation light. This facilitates the use of simple optical systems or optical fibres. A new family of oxygen-sensitive dyes, the porphyrin-ketones, has been introduced, which exhibits favorable spectral properties and decay times in the order of tens and hundreds of microseconds. This allows the use of simple optoelectronic circuitry and low-cost processing electronics. An optical oxygen sensor module has been developed with the dimensions of only 120 x 60 x 30 mm. The prototype is based on the measurement of the decay time of the luminophore by measuring the phase shift between the square-wave excitation and the detected square-wave of the emission coming from the sensor. The instrument is based on semiconductor devices (light-emitting diodes, photodiodes) and may be used for the detection of oxygen in gaseous or liquid samples. The measurement range of the device is from 0 to 200 hPa oxygen partial pressure with a resolution of < 1 hPa over the whole measurement range. The overall measurement accuracy of < +/- 1 hPa has been obtained for periods of 24 h of continuous measurement in a thermostatted environment. The sensor response times t90 are typically < 1 s for gases and 0.5 to 5 min for liquid samples.     

Protein crystals in Phycomyces sporangiophores are involved in graviperception.

The sporangiophores of the zygomycete fungus Phycomyces blakesleeanus contain octahedral crystals with diameters of up to 5 micrometers in their vacuole. The crystals are associated with the intracellular membrane system. In tilted or horizontally placed sporangiophores, the crystals sediment to the respective lower face of the vacuole with a velocity of up to 100 micrometers per minute. The sedimentation is completed within about 2 minutes, well within the latency period for the negative gravitropic response of Phycomyces. Crystal-lacking mutant strains display a smaller maximal bending angle and a reduced gravitropic bending rate in comparison to the wild type. We therefore conclude that the crystals serve as statoliths for gravitropism in Phycomyces.     

Shadow detection for mobile robots: Features,evaluation, and datasets

ABSTRACT

Shadows have long been a challenging topic for computer vision. This challenge is made even harder when we assume that the camera is moving, as many existing shadow detection techniques require the creation and maintenance of a background model. This article explores the problem of shadow modelling from a moving viewpoint (assumed to be a robotic platform) through comparing shadow-variant and shadow-invariant image features — primarily color, texture and edge-based features. These features are then embedded in a segmentation pipeline that provides predictions on shadow status, using minimal temporal context. We also release a public dataset of shadow-related image sequences, to help other researchers further develop shadow detection methods and to enable benchmarking of techniques.