Post-Band Merge Utilities Applied to Spitzer Pleiades Data

Band merging extracted point sources observed in multiple wavelength bands is generally done purely on the basis of positional information in order to avoid photometric biases. Automated merge decisions can be more optimal with better position estimation and more realistic modeling of positional estimation errors. Unfortunately, extraction software often does not provide the most accurate positional information possible, and so post-band merge utilities have been developed and implemented to refine both the source positions and the error modeling. Subsequent band merging of the refined detections improves the completeness and reliability of the multi-band source catalog. Application to Spitzer Space Telescope mapping observations of the Pleiades star cluster demonstrates some aspects of the improved band merging

Bit error rate measurement above and below bit rate tracking threshold

Bit error rate is measured by sending a pseudo-random noise (PRN) code test signal simulating digital data through digital equipment to be tested. An incoming signal representing the response of the equipment being tested, together with any added noise, is received and tracked by being compared with a locally generated PRN code. Once the locally generated PRN code matches the incoming signal a tracking lock is obtained. The incoming signal is then integrated and compared bit-by-bit against the locally generated PRN code and differences between bits being compared are counted as bit errors

Experimental study of dynamic effects of crew motion in a Manned Orbital Research Laboratory /MORL/

Disturbance profiles of routine crew motion in simulated zero gravity environment of manned orbital research laborator

Calibration of Viking imaging system pointing, image extraction, and optical navigation measure

Pointing control and knowledge accuracy of Viking Orbiter science instruments is controlled by the scan platform. Calibration of the scan platform and the imaging system was accomplished through mathematical models. The calibration procedure and results obtained for the two Viking spacecraft are described. Included are both ground and in-flight scan platform calibrations, and the additional calibrations unique to optical navigation

Proton-induced noise in digicons

The Space Telescope, which carries four Digicons, will pass several times per day through a low-altitude portion of the radiation belt called the South Atlantic Anomaly. This is expected to create interference in what is otherwise anticipated to be a noise-free device. Two essential components of the Digicon, the semiconductor diode array and the UV transmitting window, generate noise when subjected to medium-energy proton radiation, a primary component of the belt. These trapped protons, having energies ranging from 2 to 400 Mev and fluences at the Digicon up to 4,000 P+/sec-sq cm, pass through both the window and the diode array, depositing energy in each. In order to evaluate the effect of these protons, engineering test models of Digicon tubes to be flown on the High Resolution Spectrograph were irradiated with low-flux monoenergetic proton beams at the University of Maryland cyclotron. Electron-hole pairs produced by the protons passing through the diodes or the surrounding bulk caused a background count rate. This is the result of holes diffusing over a distance of many diode spacings, causing counts to be triggered simultaneously in the output circuits of several adjacent diodes. Pulse-height spectra of these proton-induced counts indicate that most of the bulk-related counts overlap the single photoelectron peak. A geometrical model will be presented of the charge collection characteristics of the diode array that accounts for most of the observed effects

Multi-physics ensemble snow modelling in the western Himalaya

Combining multiple data sources with multi-physics simulation frameworks offers new potential to extend snow model inter-comparison efforts to the Himalaya. As such, this study evaluates the sensitivity of simulated regional snow cover and runoff dynamics to different snowpack process representations. The evaluation is based on a spatially distributed version of the Factorial Snowpack Model (FSM) set up for the Astore catchment in the upper Indus basin. The FSM multi-physics model was driven by climate fields from the High Asia Refined Analysis (HAR) dynamical downscaling product. Ensemble performance was evaluated primarily using MODIS remote sensing of snow-covered area, albedo and land surface temperature. In line with previous snow model inter-comparisons, no single FSM configuration performs best in all of the years simulated. However, the results demonstrate that performance variation in this case is at least partly related to inaccuracies in the sequencing of inter-annual variation in HAR climate inputs, not just FSM model limitations. Ensemble spread is dominated by interactions between parameterisations of albedo, snowpack hydrology and atmospheric stability effects on turbulent heat fluxes. The resulting ensemble structure is similar in different years, which leads to systematic divergence in ablation and mass balance at high elevations. While ensemble spread and errors are notably lower when viewed as anomalies, FSM configurations show important differences in their absolute sensitivity to climate variation. Comparison with observations suggests that a subset of the ensemble should be retained for climate change projections, namely those members including prognostic albedo and liquid water retention, refreezing and drainage processes

Transient energy excitation in shortcuts to adiabaticity for the time dependent harmonic oscillator

There is recently a surge of interest to cut down the time it takes to change the state of a quantum system adiabatically. We study for the time-dependent harmonic oscillator the transient energy excitation in speed-up processes designed to reproduce the initial populations at some predetermined final frequency and time, providing lower bounds and examples. Implications for the limits imposed to the process times and for the principle of unattainability of the absolute zero, in a single expansion or in quantum refrigerator cycles, are drawn.Comment: 7 pages, 6 figure

Towards practical classical processing for the surface code: timing analysis

Topological quantum error correction codes have high thresholds and are well suited to physical implementation. The minimum weight perfect matching algorithm can be used to efficiently handle errors in such codes. We perform a timing analysis of our current implementation of the minimum weight perfect matching algorithm. Our implementation performs the classical processing associated with an nxn lattice of qubits realizing a square surface code storing a single logical qubit of information in a fault-tolerant manner. We empirically demonstrate that our implementation requires only O(n^2) average time per round of error correction for code distances ranging from 4 to 512 and a range of depolarizing error rates. We also describe tests we have performed to verify that it always obtains a true minimum weight perfect matching.Comment: 13 pages, 13 figures, version accepted for publicatio