Psychological factors in remote sensing: A review of some recent research

We review recent psychological research that pertains to remote sensing, with a focus on two major problem areas: The problem of eliciting and characterizing the knowledge of expert interpreters of remotely‐sensed data, and the problem of how to best utilize color in remote sensing displays. This research has immediate relevance to many remote sensing activities, but it also has broader implications. One general implication is that experimental psychology offers concepts and research methods that can be of benefit to the field of remote sensing. It is possible to discover the principles involved in the design of “good”; remote sensing displays, and the design of methods for teaching novices how to interpret remote sensing displays. A second broad implication of the psychological research is that remote sensing, as traditionally conceived, is actually just one part of a larger process of “remote perceiving.”; This idea is pursued in a second article (Hoffman, 1990), in which an attempt is made to characterize remote sensing as a unified science.     

The Queen Charlotte Fault, British Columbia: seafloor anatomy of a transform fault and its influence on sediment processes

The Queen Charlotte Fault Zone (QCFZ) off western Canada is the northern equivalent to the San Andreas Fault Zone, the Pacific–North American plate boundary. Geomorphologic expression and surface processes associated with the QCFZ system have been revealed in unprecedented detail by recent seabed mapping surveys. Convergence of the Pacific and North American plates along northern British Columbia is well known, but how the QCFZ accommodates this convergence is still a subject of controversy. The multibeam sonar bathymetry data reveal, for the first time, evidence of a fault valley with small depressions on the upper slope, offshore central Haida Gwaii (Queen Charlotte Islands). The depressions form where strike-slip right-step offsets have realigned the fault due to oblique convergence. Core stratigraphy and radiocarbon dating of sediments within the fault valley and small depressions suggest that these features are recent in origin. In addition, the development of the fault valley and dislocation of submarine canyons control sediment migration from the continental shelf through to the lower slope. This interpretation of the geomorphic expression of major plate tectonic processes along the QCFZ can now be tested with new surveys subsequent to the October 2012 magnitude 7.7 earthquake.     

Atmospheric Electrification in Dusty,Reactive Gases in the Solar System and Beyond

Detailed observations of the solar system planets reveal a wide variety of local atmospheric conditions. Astronomical observations have revealed a variety of extrasolar planets none of which resembles any of the solar system planets in full. Instead, the most massive amongst the extrasolar planets, the gas giants, appear very similar to the class of (young) brown dwarfs which are amongst the oldest objects in the Universe. Despite this diversity, solar system planets, extrasolar planets and brown dwarfs have broadly similar global temperatures between 300 and 2500 K. In consequence, clouds of different chemical species form in their atmospheres. While the details of these clouds differ, the fundamental physical processes are the same. Further to this, all these objects were observed to produce radio and X-ray emissions. While both kinds of radiation are well studied on Earth and to a lesser extent on the solar system planets, the occurrence of emissions that potentially originate from accelerated electrons on brown dwarfs, extrasolar planets and protoplanetary disks is not well understood yet. This paper offers an interdisciplinary view on electrification processes and their feedback on their hosting environment in meteorology, volcanology, planetology and research on extrasolar planets and planet formation.     

Observations of methanol masers in star-forming regions

We present VLBI observations of 6.7 and 12.2 GHz methanol masers in three star-forming regions, NGC7538, W75N and S252. Our results reveal linear structures in the VLBI maps and monotonic velocity gradients in the three sources. All these results are consistent with Keplerian disks of diameter of 1000–2000 AU around young stars of mass (10–30) M.     

Single-point position estimation in interplanetary trajectories using star trackers

This study provides a single-point position estimation technique for interplanetary missions by observing visible planets using star trackers. Closed-form least-squares solution is obtained by minimizing the sum of the expected object-space squared distance errors. A weighted least-squares solution is provided by an iterative procedure. The weights are evaluated using the distances to the planets estimated by the least-squares solution. It is shown that the weighted approach only requires one iteration to converge and results in significant accuracy gains compared to simple least squares approach. The light-time correction is taken into account while the star-light aberration cannot be implemented in single-point estimation as it requires knowledge of the observer velocity. The proposed method is numerically validated through a statistical scenario as follows. A three-dimensional grid of test cases is generated: two dimensions sweep through the ecliptic plane and the third dimension sweeps through time from January 1, 2018 to January 1, 2043 in 5-year increments. The observer position is estimated at each test case and the estimate error is recorded. The results obtained show that a large majority of positions are well suited to position estimation by using star trackers pointing to visible planets, and reliable and accurate single-point position estimations can be provided in interplanetary missions. The proposed approach is suitable to be used to initiate a filtering technique to increase the estimation accuracy.     

The effect of wave generation on HXR bremsstrahlung spectra from flare thick-target beams

Fast electrons in the solar atmosphere are detected by their hard X-ray bremsstrahlung and by type III radio bursts caused by ‘bump-on-tail’ plasma wave generation. This paper investigates empirically the effect of wave generation on the HXR spectrum. Purely collisional propagation of an electron beam generates a bump in the distribution function, due to stopping of low-velocity electrons. The consequent positive gradient means there is a possibility of wave generation, production of type III radio bursts, and energy redistribution of the electron beam. We have represented this relaxation parametrically and calculated the global bremsstrahlung HXR emission spectrum. We show that for a range of relaxed forms, with different local electron spectral shapes, the bremsstrahlung spectrum integrated over the whole target is identical in shape to the purely collisionally evolved beam. Our results show that spatially integrated HXR spectral measurements would be unable to distinguish between the presence or absence of relaxation effects. Only spatially resolved hard X-ray spectra, such as anticipated from the HESSI mission, will be able to remove this ambiguity in HXR diagnostics of beam relaxation.     

Palaeoecological investigations towards the reconstruction of the post-glacial environment at Lough Doo,County Mayo,Ireland

Results of palaeoecological studies involving pollen analytical, chemical and palaeomagnetic investigations on a 3 m core from Lough Doo, NE County Mayo, are presented. The record, which commences shortly after 7000 BP, shows a sharp Alnus expansion coinciding with a decline in Pius at 6400 BP, an elm decline taking place in the context of severe soil erosion and the final decline of Pinus occurring as the chemical record indicates onset of severe reducing conditions in the catchment. Pine becomes extinct at or shortly before 3200 BP in the context of increased farming activity and the expansion of blanket bog in the adjacent upland areas. A later feature (c. 1880 BP) is the expansion of Taxus to 7.1% of total pollen. On the basis of the palynological evidence, it is concluded that there were no major Neolithic Landnam phases, which contrasts sharply with the evidence for widespread woodland clearance and the laying out of extensive and regular field systems in the northern coastal part of County Mayo. In the upper part of the core a severe inversion of ¹⁴C dates is recorded. On the basis of the palaeomagnetic and pollen evidence this began at c. 1500 BP and is considered to have been initiated in the context of woodland clearance and a renewal in farming activity.     

NGC7538 Irs1 N: Modeling a Circumstellar Maser Disk

We present an edge-on Keplerian disk model to explain the main component of the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1N. The brightness distribution and spectrum of the line of bright masers are successfully modeled with high amplification of background radio continuum emission along velocity coherent paths through a maser disk. The bend seen in the position–velocity diagram is a characteristic signature of differentially rotating disks. For a central mass of 30M, suggested by other observations, our model fixes the masing disk to have inner and outer radii of 270 and 750 AU.