The THEMIS Digital Fields Board

The Digital Fields Board (DFB) performs the data acquisition and signal processing for the Electric Fields Instrument and Search Coil Magnetometer on each of the THEMIS (Time History of Events and Macroscale Interactions during Substorms) satellites. The processing is highly flexible and low-power (～1.1 watt orbit-averaged). The primary data products are time series waveforms and wave power spectra of the electric and magnetic fields. The power spectra can be computed either on the raw signals (i.e. in a system co-rotating with the spacecraft) or in a coordinate system aligned with the local DC magnetic field. Other data products include spectral power from multiple passbands (filter banks) and electric power in the 30–500 kHz band. The DFBs on all five spacecraft have been turned on and checked out in-flight, and are functioning as designed.     

Satellite observations of power line harmonic radiation

In-situ spectral observations of power-line harmonic radiation (PLHR) are still quite rare and almost all the detailed characteristics have been derived from studies at Antarctic stations such as Siple and Halley, and their conjugates in North America. Because of the lack of more direct satellite evidence of PLHR and the difficulties in interpretation of morphological studies, such as those of Ariel 3 and 4, there is considerable controversy concerning the relative importance of PLHR and its contribution to wave-particle interactions (WPI) in the magnetosphere. The early Ariel 3 and 4 global surveys indicated that, in terms of true mean wave energy, there is no longitudinal localisation, the contribution of world-wide intense VLF emissions, associated with magnetic storms, being dominant. Also, the most intense wave emission, that of plasmaspheric hiss at ELF (< 1 kHz) exhibits little evidence of localisation. The PLHR phenomenon is most conspicuous by its persistence in quiet times (Kp ≤ 2+) at 45° < Λ < 55° over North America and its conjugate region, even though the less frequent strongest emissions, to which it gives rise in the summer, are located polewards at 3 < L < 5. In the northern winter, when spheric activity over both North America and its conjugate are low, there is a high occurrence of strong discrete emissions, which are more sharply localised than in the summer, on the NE industrial U.S.A. field line. The most recent Ariel 4 studies, particularly on the spheric wavefield over North America (using data from the Appleton Laboratory impulse counters) and on the character of the wavefield over the mainland and over the Atlantic immediately to the east (where the spheric contribution is similar) throw new light on the problem. It appears that the principal role of the PLHR may be to sustain duct structure and multihop propagation which is relatively much rarer over the Atlantic. Typical industrial PLHR consists of a series of narrow pulses at twice the mains frequency. It is suggested that these ‘artificial spherics’ may help to sustain the WPI and multihop duct structure. At L = 4, Yoshida et al. (1980) have shown that there is a strong, sharp maximum for WPIs originating in spherics, at f ? 3 kHz, in good agreement with Siple observations.     

Error Covariance Analysis of a Karhunen-Loeve Collocation Estimator

An error covariance analysis of a two-dimensional gravity compensation technique (KLC) employing a Karhunen-Loeve gravity disturbance model and the linear least-square collocation algorithm for its estimation is presented, without actually using any data. Its performance is compared with another gravity compensation technique (KLE), whose error covariance analysis was previously presented by Gupta. From the mismodeling analysis, KLC appears to be superior to KLE.     

Characteristics and performance of thin LaBr3(Ce) crystal for hard X-ray astronomy

We have developed a new detector using thin lanthanum bromide crystal (32 × 3 mm) for use in X-ray astronomy. The instrument was launched in high altitude balloon flight on two different occasions, December 21, 2007, which reached a ceiling altitude of 4.3 mbs and April 25, 2008 reaching a ceiling altitude 2.8 mbs. The observed background counting rate at the ceiling altitude of 4 mbs was ∼4 × 10⁻³ ct cm⁻² s⁻¹ keV⁻¹ sr⁻¹. This paper describes the details of the experiment, the detector characteristics, and the background behaviour at the ceiling altitude.     

Magnetic Turbulence in the Geospace Environment

Magnetic turbulence is found in most space plasmas, including the Earth’s magnetosphere, and the interaction region between the magnetosphere and the solar wind. Recent spacecraft observations of magnetic turbulence in the ion foreshock, in the magnetosheath, in the polar cusp regions, in the magnetotail, and in the high latitude ionosphere are reviewed. It is found that: 1. A large share of magnetic turbulence in the geospace environment is generated locally, as due for instance to the reflected ion beams in the ion foreshock, to temperature anisotropy in the magnetosheath and the polar cusp regions, to velocity shear in the magnetosheath and magnetotail, and to magnetic reconnection at the magnetopause and in the magnetotail. 2. Spectral indices close to the Kolmogorov value can be recovered for low frequency turbulence when long enough intervals at relatively constant flow speed are analyzed in the magnetotail, or when fluctuations in the magnetosheath are considered far downstream from the bow shock. 3. For high frequency turbulence, a spectral index α?2.3 or larger is observed in most geospace regions, in agreement with what is observed in the solar wind. 4. More studies are needed to gain an understanding of turbulence dissipation in the geospace environment, also keeping in mind that the strong temperature anisotropies which are observed show that wave particle interactions can be a source of wave emission rather than of turbulence dissipation. 5. Several spacecraft observations show the existence of vortices in the magnetosheath, on the magnetopause, in the magnetotail, and in the ionosphere, so that they may have a primary role in the turbulent injection and evolution. The influence of such a turbulence on the plasma transport, dynamics, and energization will be described, also using the results of numerical simulations.     

RPC-ICA: The Ion Composition Analyzer of the Rosetta Plasma Consortium

The Ion Composition Analyzer (ICA) is part of the Rosetta Plasma Consortium (RPC). ICA is designed to measure the three-dimensional distribution function of positive ions in order to study the interaction between the solar wind and cometary particles. The instrument has a mass resolution high enough to resolve the major species such as protons, helium, oxygen, molecular ions, and heavy ions characteristic of dusty plasma regions. ICA consists of an electrostatic acceptance angle filter, an electrostatic energy filter, and a magnetic momentum filter. Particles are detected using large diameter (100 mm) microchannel plates and a two-dimensional anode system. ICA has its own processor for data reduction/compression and formatting. The energy range of the instrument is from 25 eV to 40 keV and an angular field-of-view of 360° × 90° is achieved through electrostatic deflection of incoming particles.     

Hectometer radio bursts and energetic electrons during solar flares according to observations onboard the Interball-1 satellite

Radio bursts in the frequency range 100–1500 kHz and fluxes of energetic electrons with energies of 20–450 keV recorded onboard the Interball-1 satellite during prominent chromospheric flares on the Sun are studied. The time of propagation of the electrons to the Earth is estimated using the method of comparison of the moments of the beginning of radio emission generation during the explosive phase of the flare and the arrival of the accelerated electrons to the Earth.     

ISE: intelligent synthesis environment for future aerospace systems

The Intelligent Synthesis Environment (ISE) being developed by NASA, UVA, and JPL for significantly enhancing the rapid creation of innovative affordable products and missions is described. ISE uses a synergistic combination of leading-edge technologies, including high-performance computing, high-capacity communications and networking, virtual product development, knowledge-based engineering, computational intelligence, human-computer interaction, and product information management. The environment will link scientists, design teams, manufacturers, suppliers, and consultants who participate in the mission synthesis, as well as in the creation and operation of the aerospace system. It will radically advance the process by which complex science missions are synthesized, and high-tech engineering systems are designed, manufactured, and operated. The evolution of engineering design is described along with the shortcomings of current product development techniques. The need for ISE to create high-science payoff missions and aerospace systems at affordable costs is discussed. The five major components critical to ISE and some of their sub-elements are described: namely, human-ISE interaction; infrastructure for distributed collaboration; rapid synthesis and simulation tools; intelligent life-cycle system integration; and cultural change in the creative process. Related government and industry programs are outlined and future impact of ISE on complex missions and aerospace systems is discussed.     

On mapping a tracking algorithm onto parallel processors

The problem of mapping the tasks of a multitarget tracking algorithm onto parallel computing architectures to maximize speedup is considered. An asymptotically optimal mapping algorithm is developed and applied to study the effects of task granularity and processor architectures on the speedup. From the simulation results, it is concluded that task granularity and the parallelization of clustering and global hypotheses formation stages of the tracking algorithm are major determinants of speedup