Vertical motions in Thailand after the 2004 Sumatra–Andaman Earthquake from GPS observations and its geophysical modelling

Following previous findings from ongoing GPS research in Thailand since 2004 we continue to exploit the GPS technique to monitor and model land motions induced by the Sumatra–Andaman Earthquake. Our latest results show that up to the end of 2010, Thailand has been co-seismically displaced and is subsequently undergoing a post-seismic horizontal deformation with total displacements (co-seismic plus post-seismic) ranging from 10.5 to 74.7 cm. We observed the largest horizontal displacements in the southern part of Thailand and moderate and small displacements in the central and northern parts. In addition to horizontal displacements throughout Thailand, continuous GPS measurements show that large parts of Thailand are subsiding at rates up to 1 cm/yr. It is the first time that such vertical post-seismic deformations at large distances (650–1500 km away from the Earthquake’s epicentre) have been recorded. We have investigated the physical processes leading to the observed subsidence. While after-slip on the subduction interface induces negligible or even slightly positive vertical motions, relaxation in the asthenosphere is associated with a sizable subsidence. Predictions from a 3D finite element model feature an asthenosphere with an effective viscosity of the order of 3 * 10¹⁸ Pas, fit the horizontal post-seismic data and the observed subsidence well. This model is then used to predict the subsidence over the whole seismic cycle. The subsidence should go on with a diminishing rate through the next two decades and its final magnitude should not exceed 10 cm in the Bangkok area.     

On the convergence of iterative methods for bearings-only tracking

This paper deals with the analysis of the convergence of iterative methods for bearings only tracking (BOT). A geometric and unified framework is developed. Explicit sufficient conditions ensuring convergence of iterative methods for maximization of the likelihood functional are then derived     

FAST FEATURE RANKING AND ITS APPLICATION TO FACE RECOGNITION

A fast feature ranking algorithm for classification in the presence of high dimensionahty and small sample size is proposed. The basic idea is that the important features force the data points of the same class to maintain their intrinsic neighbor relations, whereas neighboring points of different classes are no longer to stick to one an- other. Applying this assumption, an optimization problem weighting each feature is derived. The algorithm does not involve the dense matrix eigen-decomposition which can be computationally expensive in time. Extensive exper- iments are conducted to validate the significance of selected features using the Yale, Extended YaleB and PIE data- sets. The thorough evaluation shows that, using one-nearest neighbor classifier, the recognition rates using 100-- 500 leading features selected by the algorithm distinctively outperform those with features selected by the baseline feature selection algorithms, while using support vector machine features selected by the algorithm show less prominent improvement. Moreover, the experiments demonstrate that the proposed algorithm is particularly effi- cient for multi-class face recognition problem.     

Accuracy of Star Occultation Measurements for Satellite Navigation

To determine the orbital parameters of a satellite using star occultations, it is necessary to measure the intensity of stars as they occult. The accuracy of the intensity measurements is reduced by interfering sources of light and internal noise, and is expressed in terms of the magnitude of various sources of interference. Subsequently, a specific system is analyzed in detail. Moonlit cloud tops introduce the largest systematic error. Photon noise from the star radiation, airglow, and moonlit cloud tops are the largest sources of random errors.     

Emesis and space motion sickness in amphibians.

Amphibians possess the ability to vomit in response to a variety of stimuli that provoke emesis in mammals. Pharmacological studies have establish that the ejection of gastric contents and the basic mechanism for vomiting have been phylogenetically conserved among these tetrapods. As part of on-going comparative studies on emesis in vertebrates, we previously documented that some postmetamorphic anurans and salamander larvae experience motion-induced emesis when exposed to the provocative stimulus of parabolic aircraft flight. However, more recent experiments suggest that there are strict conditions for inducing emesis in amphibians exposed to parabolic flight and that amphibians are not as sensitive to this stimulus as mammals. Further studies on emesis in lower vertebrates may help us understand the processes that cause emesis in abnormal gravitational regimes.     

Determination of parameters of rotational motion of the <Emphasis Type="Italic">Monitor-E</Emphasis> spacecraft from the telemetry data on solar batteries’ current

The Monitor-E spacecraft executed uncontrolled flight due to emergency situation, no telemetry information on parameters of the spacecraft’s attitude motion being available. So, the problem arose to determine the spacecraft’s rotational motion from the accessible indirect information—the electric current provided by solar batteries. In this paper the integrated statistical technique is described, that allows one to solve this problem. The values of current, obtained over the time interval some tens of minutes long, have been processed simultaneously by the least squares method using the integration of the equations of spacecraft’s rotational motion. As a result of processing, the initial conditions of motion were estimated, and the spacecraft’s moments of inertia were updated, as well as the angles, specifying solar batteries position in the spacecraft-fixed coordinate system. The results of processing of 12 data sets are presented, which allowed us to reconstruct the actual rotational motion of the spacecraft.     

A Test of the Effect of Satellite Spin on Two-Way Doppler Range-Rate Measurements

Analysis indicates that the rotation of a satellite can cause an error in the range-rate measurements of a two-way Doppler tracking system. The error is proportional to the rotation rate, and the constant of proportionality depends on the polarization of the satellite transponder antennas. Measurements made by ground-based simulation confirmed the analytical prediction.     

Report on the Geneva Space Telecommunications Conference? Broadcasting Aspects

The growth of the Intelsat Global Commercial Communications Satellite System, which provides the facilities used to exchange television programs among many countries of the world, is described. Service was initiated between North America and Western Europe in 1965. Currently, some 48 separate geographic areas throughout the world are interconnected by the Intelsat System. The unique air-transportable Earth terminal, developed by the General Electric Company, at the request of the television networks, to meet the special requirements for providing live television coverage in color of the Apollo recoveries at sea, will also be described.