2–10 KeV spectra of Crab-like SNR's as observed by EXOSAT

The EXOSAT ME observations of 3C58 and G21.5-0.9 are presented. The data for these objects is considered in conjunction with the data available from EXOSAT for the Crab-like SNR's Crab and Vela X. The objects have single power law spectra with a range of spectral indices of 0.6 to 1.5, 3C58 and Vela X being similar to the Crab whilst G21.5-0.9 and the source associated with the Vela pulsar have significantly flatter spectra. The derived column density for G21.5-0.9 is consistent with a distance of 5 kpc. The X-ray luminosities and overall electromagnetic spectra of these objects are investigated as age indicators and compared to current model predictions.     

Optimum Windows for Image Registration

Two-dimensional cross-correlation techniques are applied to the problem of image registration under the assumption of small geometric distortion. Optimum window functions are derived for two performance measures of interest: peak-to-sidelobe ratio and mean-square registration error. The latter is examined in terms of the contribution caused by noise and the contribution caused by geometric distortion. A generalized Lagrange multiplier approach is used to derive approximate solutions assuming random images. The case of Gaussian autocorrelation functions is examined in detail. Results of applying the theoretically derived window functions to real data are presented, showing significant improvement in correlator performance.     

The Medium Energy Instrument on Exosat

The Medium Energy Instrument on EXOSAT, although conceived as the main instrument for occultations, has been made sufficiently versatile to provide a significant advance over previous large area proportional counters when used for individual source studies of timing and spectra. The energy range is 1.2 to 50 keV, with E/E of 0.2 at 6 keV, sufficient to detect iron lines. The effective area of 1800 cm² and narrow field of view (3/4° × 3/4°) make it suitable for the detailed study of sources down to the 0.3 mCrab confusion limit. The unique facility provided by EXOSAT, allowing uninterrupted observations of X-ray sources for periods of up to 80 hours, backed up by a high capacity data link and on-board processing, enables timing studies to be performed over the range from milliseconds to days. Sophisticated background discrimination techniques giving a rejection efficiency of99% will control the background count rate to a suitably low value in the environment of the 200,000 km orbit.     

Energy deposition rates by charged particles measured during the energy budget campaign

Measurements of the precipitation of electrons and positive ions (in the keV to MeV range) detected aboard eight rockets launched from Northern Scandinavia are reported together with corresponding satellite data. The downgoing integral fluxes indicate the temporal fluctuations during each flight. Height profiles of the energy deposition into the atmosphere at different levels of geomagnetic disturbance are given.     

Communicating bioastronautics research to students, families and the nation

The National Space Biomedical Research Institute (NSBRI) is supporting the National Aeronautics and Space Administration's (NASA) education mission through a comprehensive Education and Public Outreach Program (EPOP) that communicates the excitement and significance of space biology to schools, families, and lay audiences. The EPOP is comprised of eight academic institutions: Baylor College of Medicine, Massachusetts Institute of Technology, Morehouse School of Medicine, Mount Sinai School of Medicine, Texas A&M University, University of Texas Medical Branch Galveston, Rice University, and the University of Washington. This paper describes the programs and products created by the EPOP to promote space life science education in schools and among the general public. To date, these activities have reached thousands of teachers and students around the US and have been rated very highly.     

A thermodynamic analysis of microbial growth experiments

The common thread of energy release suggests that diverse microbial metabolic processes can be compared through thermodynamic analyses. The resulting energy and power requirements can provide quantitative constraints on habitability. Because previous thermodynamic analyses have focused on the minimum amount of energy needed for the growth of a microorganism or community, the focus of this study is to gain a fuller understanding of the microbial response to highly habitable conditions. This communication summarizes the results of a thermodynamic analysis of the energy and power consumed by microorganisms in experiments that were designed to optimize growth. Reports of microbial growth experiments taken from the literature were combined with speciation and standard state calculations to assess the overall Gibbs energy change during the experiments. Results show that similar numbers of cells (10(9) to 10(10) ) were produced in these experiments regardless of the duration of log phase growth (from <2 to >200 hours) or the total Gibbs energy change [from 1.3-29.6 kJ (mol electrons transferred)(1)]. As a result, optimal growth conditions appear to produce between 10(10) and 10(14) cells per watt of power consumed.     

President Obama’s National Space Policy: A change in tone and a focus on space sustainability

The major features of President Obama’s new US space policy are discussed and particular aspects are compared with those of the previous Bush policy. In many cases there are similarities of substance but the tone of the latest policy is more outward looking and inclusive, with a far greater emphasis on cooperation, both internationally and with the private sector. And while some complain that the policy does not sufficiently emphasize US leadership, a statement by President Obama on the day of its release makes clear that this remains a paramount goal. Serious questions remain, however, about implementation of the new policy, particularly where it requires substantial government funding such as human spaceflight and the restructured weather/environmental satellite programs.     

Following the kinetics: iron-oxidizing microbial mats in cold icelandic volcanic habitats and their rock-associated carbonaceous signature

Icelandic streams with mean annual temperatures of less than 5 °C, which receive the cationic products of basaltic rock weathering, were found to host mats of iron-cycling microorganisms. We investigated two representative sites. Iron-oxidizing Gallionella and iron-reducing Geobacter species were present. The mats host a high bacterial diversity as determined by culture-independent methods. β-Proteobacteria, Actinobacteria, α-Proteobacteria, and Bacteroidetes were abundant microbial taxa. The mat contained a high number of phototroph sequences. The carbon compounds in the mat displayed broad G and D bands with Raman spectroscopy. This signature becomes incorporated into the weathered oxidized surface layer of the basaltic rocks and was observed on rocks that no longer host mats. The presence of iron-oxidizing taxa in the stream microbial mats, and the lack of them in previously studied volcanic rocks in Iceland that have intermittently been exposed to surface water flows, can be explained by the kinetic limitations to the extraction of reduced iron from rocks. This type of ecosystem illustrates key factors that control the distribution of chemolithotrophs in cold volcanic environments. The data show that one promising sample type for which the hypothesis of the existence of past life on Mars can be tested is the surface of volcanic rocks that, previously, were situated within channels carved by flowing water. Our results also show that the carbonaceous signatures of life, if life had occurred, could be found in or on these rocks.     

ISCCP cloud analysis algorithm intercomparison

The International Satellite Cloud Climatology Project (ISCCP) will provide a uniform global climatology of satellite-measured radiances and derive a climatology of cloud radiative properties from these radiances. For this purpose, a pilot study of cloud analysis algorithms was initiated to define a state-of-the-art algorithm for ISCCP. This study compared the results of applying the nine different algorithms to the same satellite radiance data. The comparison allowed for a sharper understanding of the process of detecting clouds and shows that all algorithms can be improved by better information about clear sky radiance values (essentially equivalent to surface property information) and by better understanding of cloud size distribution variations. The dependence of all methods on cloud size distribution led to selection of an advanced bispectral threshold technique for ISCCP because this method is currently better understood and more developed. Further research on cloud algorithms is clearly suggested by these results.