Instantaneous BeiDou–GPS attitude determination: A performance analysis

The advent of modernized and new global navigation satellite systems (GNSS) has enhanced the availability of satellite based positioning, navigation, and timing (PNT) solutions. Specifically, it increases redundancy and yields operational back-up or independence in case of failure or unavailability of one system. Among existing GNSS, the Chinese BeiDou system (BDS) is being developed and will consist of geostationary (GEO) satellites, inclined geosynchronous orbit (IGSO) satellites, and medium-Earth-orbit (MEO) satellites. In this contribution, a BeiDou–GPS robustness analysis is carried out for instantaneous, unaided attitude determination.     

WIND/3DP and Nancay radioheliographobservations of solar energetic electron events

Initial results of a combined study of electron events using the 3DP experiment on the WIND spacecraftand the Nançay Radioheliograph (NRH) are presented. A total of 57 electron events whose solar release time could be inferred from WIND/3DP observations occurred during NRH observing times. In 40 of them a distinct signature was detected in maps at decimetric and metric wavelengths (dm-m-λ) taken by the NRH. These events are equally distributed among two categories: (1) Electron release together with dm-m-λ bursts of a few minutes duration: these events are also accompanied by decametric-hectometric type III bursts seen by WAVES/WIND. They correspond to the well-known impulsive electron events. (2) Electron release during long duration (several tens of minutes) dm-m-λ emission: the electrons are most often released more than ten minutes after the start of the radio event. In the majority of cases the dm-m-λ radio source changes position, size, and/or intensity near the time of electron release.     

Escaping near-relativistic electron beams from the solar corona

Processes in the solar corona are prodigious accelerators of energetic ions, and electrons. The angular distribution, composition, and spectra of energetic particles observed near Earth gives information on the acceleration mechanisms. A class of energetic particle observations particularly useful in understanding the solar acceleration is the near-relativistic impulsive beam-like electron events. During five years of operation the Advanced Composition Explorer (ACE) has measured well over 400 electron events. Approximately 25% of these electron events are impulsive beam-like events that are released onto interplanetary field lines predominantly from western solar longitudes. We extend our initial 3 year study during the rise to solar maximum (Haggerty and Roelof, 2002; Simnett et al., 2002) to a five year statistical analysis of these beam-like energetic electron events in relationship to optical flares, microwave emission, soft X-ray emission, metric and decametric type-III radio bursts, and coronal mass ejections.     

The Scanning Sky Monitor (SSM) on ASTROSAT

The Scanning Sky Monitor is one of the experiments onboard the ASTROSAT, an Indian multiwavelength astronomy satellite mission. This experiment will detect and monitor X-ray transients in the energy band 2–10 keV. It is similar in design to the ASM on RXTE. It consists of position-sensitive proportional counters with one-dimensional mask. We describe the configuration of the experiment. We also discuss some of the results obtained using a detector which has already been fabricated and tested in our laboratory.     

Two years of INTEGRAL observation of the BHC IGR J17464-3213

On March 2003, IBIS, the γ-ray imager on board the INTEGRAL satellite, detected an outburst from a new source, IGR J17464-3213, that turned out to be an HEAO-1 transient, namely H1743-322. The spectral and temporal evolutions of the source were observed by INTEGRAL in different periods. Also RXTE observed the source for the first time on 2003 March 29 during a PCA Galactic bulge scan. The source flux decayed below the RXTE PCA sensitivity limit in November 2003, then in April 2004 it was again detected by INTEGRAL. On July 3, 2004 the source was again detected by RXTE/PCA at a 2–10 keV intensity of 16 mCrab and on July 7, reached 69 mCrab. Recently, a new outburst was observed on August 2005. We briefly summarise here the behaviour of the source observed by INTEGRAL from March 2003 to August 2005. The new outbursts of the source and the analysis of all the data collected (now public) give a global view of the spectral and time behaviour of this X-ray transient.     

Multiband echo tomography of Sco X-1

We present preliminary results of a simultaneous X-ray/optical campaign of the prototypical LMXB Sco X-1 at 1–10 Hz time resolution. Lightcurves of the high excitation Bowen/HeII emission lines and a red continuum at λ_c  6000 Å were obtained through narrow interference filters with ULTRACAM, and these were cross-correlated with simultaneous RXTE X-ray lightcurves. We find evidence for correlated variability, in particular when Sco X-1 enters the Flaring branch. The Bowen/HeII lightcurves lag the X-ray lightcurves with a light travel time which is consistent with reprocessing in the companion star while the continuum lightcurves have shorter delays consistent with reprocessing in the accretion disc.     

FEM code simulation of the magnetospheric proton fluxes

We report a study of the numeric solution to the diffusive transport equation for energetic protons magnetically trapped in the Earth's equatorial magnetosphere. The analysis takes into account the pertinent physical processes in this region, including deceleration of protons by Coulomb collisional interactions with free and bound electrons, the charge exchange process, cosmic ray albedo neutron decay source, and electric and magnetic radial diffusion. These results were obtained using the Finite Element Method with magnetic moment and geomagnetic L-shell as free variables. Steady state boundary conditions were imposed at L=1 as zero distribution function and at L=7 with proton distribution function extracted from ATS 6 satellite observations. The FEM-code yields unidirectional proton flux in the energy range of 0.1–1000 MeV at the equatorial top of the geomagnetic lines, and the results are found to be in satisfactorily agreement with the empirical NASA AP-8 model proton flux within the energy range of 0.5–100 MeV. Below 500 keV, the empirical AP-8 model proton fluxes are several orders of magnitude greater than those computed with the FEM-code at L<3. This discrepancy is difficult to explain by uncertainties of boundary spectrum parameters or transport coefficients.     

Life sciences flight hardware development for the International Space Station.

During the construction phase of the International Space Station (ISS), early flight opportunities have been identified (including designated Utilization Flights, UF) on which early science experiments may be performed. The focus of NASA's and other agencies' biological studies on the early flight opportunities is cell and molecular biology; with UF-1 scheduled to fly in fall 2001, followed by flights 8A and UF-3. Specific hardware is being developed to verify design concepts, e.g., the Avian Development Facility for incubation of small eggs and the Biomass Production System for plant cultivation. Other hardware concepts will utilize those early research opportunities onboard the ISS, e.g., an Incubator for sample cultivation, the European Modular Cultivation System for research with small plant systems, an Insect Habitat for support of insect species. Following the first Utilization Flights, additional equipment will be transported to the ISS to expand research opportunities and capabilities, e.g., a Cell Culture Unit, the Advanced Animal Habitat for rodents, an Aquatic Facility to support small fish and aquatic specimens, a Plant Research Unit for plant cultivation, and a specialized Egg Incubator for developmental biology studies. Host systems (Figure 1A, B: see text), e.g., a 2.5 m Centrifuge Rotor (g-levels from 0.01-g to 2-g) for direct comparisons between g and selectable g levels, the Life Sciences Glovebox for contained manipulations, and Habitat Holding Racks (Figure 1B: see text) will provide electrical power, communication links, and cooling to the habitats. Habitats will provide food, water, light, air and waste management as well as humidity and temperature control for a variety of research organisms. Operators on Earth and the crew on the ISS will be able to send commands to the laboratory equipment to monitor and control the environmental and experimental parameters inside specific habitats. Common laboratory equipment such as microscopes, cryo freezers, radiation dosimeters, and mass measurement devices are also currently in design stages by NASA and the ISS international partners.     

Molecular alterations in tumorigenic human bronchial and breast epithelial cells induced by high LET radiation.

Carcinogenesis is a multi-stage process with sequence of genetic events governing the phenotypic expression of a series of transformation steps leading to the development of metastatic cancer. In the present study, immortalized human bronchial (BEP2D) and breast (MCF-10F) cells were irradiated with graded doses of either 150 keV/micrometer alpha particles or 1 GeV/nucleon 56Fe ions. Transformed cells developed through a series of successive steps before becoming tumorigenic in nude mice. Cell fusion studies indicated that radiation-induced tumorigenic phenotype in BEP2D cells could be completely suppressed by fusion with non-tumorigenic BEP2D cells. The differential expressions of known genes between tumorigenic bronchial and breast cells induced by alpha particles and their respective control cultures were compared using cDNA expression array. Among the 11 genes identified to be differentially expressed in BEP2D cells, three (DCC, DNA-PK and p21(CIP1)) were shown to be consistently down-regulated by 2 to 4 fold in all the 5 tumor cell lines examined. In contrast, their expressions in the fusion cell lines were comparable to control BEP2D cells. Similarly, expression levels of a series of genes were found to be altered in a step-wise manner among tumorigenic MCF-10F cells. The results are highly suggestive that functional alterations of these genes may be causally related to the carcinogenic process.     

Development of thermal sensors and drilling systems for lunar and planetary regoliths

We consider some novel concepts for thermal properties experiments aboard lunar landers or rovers, that may lead to an improved understanding of both the structure of the lunar near surface layers and the lunar thermal history. The new instruments could be developed using the experience and heritage from recently developed systems, like the Rosetta Lander thermal conductivity experiment MUPUS and existing designs used for terrestrial measurements of thermal conductivity. We describe shortly the working principle of such sensors and the main challenges faced when using them in the airless regolith layers of the Moon or other airless bodies. In addition new concepts to create appropriate drill holes for thermal and other measurements in the lunar regolith are discussed.