Optical search for extraterrestrial intelligence with Air Cerenkov telescopes

We propose using large Air Cerenkov telescopes (ACTs) to search for optical, pulsed signals from extraterrestrial intelligence. Such dishes collect tens of photons from a nanosecond-scale pulse of isotropic equivalent power of tens of solar luminosities at a distance of 100 pc. The field of view for giant ACTs can be on the order of 10 square degrees, and they will be able to monitor 10-100 stars simultaneously for nanosecond pulses of about 6th magnitude or brighter. Using the Earth's diameter as a baseline, orbital motion of the planet could be detected by timing the pulse arrivals.     

ESA developments in life support technology: achievements and future priorities.

Following an enthusiastic start in 1985, ESA's life support technology development programme was re-assessed in the mid- to late-1990s to reflect the strong reduction in European manned space ambitions which occurred at that time. Further development was essentially restricted to activities that could constitute ISS upgrades or enhancements, or support ISS utilisation/operations, together with a single, limited, activity (MELISSA) aimed at bioregenerative life support, in the continuing hope that there might be "life after Station". The paper describes the current status of these activities and summarises the main priorities for future development that were identified at the April 1999 Workshop on Advanced Life Support.     

Intelligent control of a planning system for astronaut training

This work intends to design, analyze and solve, from the systems control perspective, a complex, dynamic, and multiconstrained planning system for generating training plans for crew members of the NASA-led International Space Station. Various intelligent planning systems have been developed within the framework of artificial intelligence. These planning systems generally lack a rigorous mathematical formalism to allow a reliable and flexible methodology for their design, modeling, and performance analysis in a dynamical, time-critical, and multiconstrained environment. Formulating the planning problem in the domain of discrete-event systems under a unified framework such that it can be modeled, designed, and analyzed as a control system will provide a self-contained theory for such planning systems. This will also provide a means to certify various planning systems for operations in the dynamical and complex environments in space. The work presented here completes the design, development, and analysis of an intricate, large-scale, and representative mathematical formulation for intelligent control of a real planning system for Space Station crew training. This planning system has been tested and used at NASA-Johnson Space Center     

EUVITA — An extreme UV imaging telescope array with spectral capability

EUVITA is a set of 8 extreme UV normal incidence imaging telescopes, each of them sensitive in a narrow band (λ/Δλ = 15 to 80), centered at wavelengths between 50 and 175 Å. Each telescope has an effective area of a few cm²; a field of view of 1.2° and a spatial resolution of 10 arcsec.

EUVITA will be flown on the Russian mission SPECTRUM X-G. This satellite will be launched in a highly eccentric orbit with a period of 4 days, allowing long, uninterrupted observations (e.g. 10⁵ seconds). EUVITA's narrow spectral bands allow the measurement of source parameters such as temperature or power law index as well as interstellar absorption, and will resolve groups of strong lines emitted by optically thin hot plasmas.     

Force sensitivity of plant gravisensing.

Rotation at 4, 10, 50 and 100 rpm on a horizontal clinostat and in microgravity exerts limited effects on the morphogenesis of lettuce and cress root statocytes and statoliths if compared with the vertical control or 1 g spaceflight reference centrifuge. However, the average distance of statoliths from the distal wall increases. The pattern of plastid location of microgravity-grown and that of clino-rotated samples has been determined at 10, 50, and 100 rpm. Experiments on the centrifuge-clinostat and spaceflight centrifuge (acceleration forces of 0.005 to 1 g) revealed that the average statolith location depends on the amplitude of acropetally or basipetally directed mass acceleration. Decreasing the acropetally directed force from 1 g to 0.4 g dislocates statoliths towards the cell center possibly mediated by the elastic forces of the cytoskeleton. In statocytes formed on the clinostat or in microgravity, the majority of statoliths are located at the center of the cell. To force the statoliths from the center of the statocyte towards one of its poles, a threshold mass acceleration of 0.01 g is required. Statocytes with centrally-located statoliths are considerably more effective in transducing a gravistimulus than those with distally-located plastids. The latent time of the graviresponse is shorter and the response itself is enhanced in roots grown on the clinostat compared to vertically grown samples. The early phases of graviperception are independent of root growth conditions since presentation time and g-threshold are similar for roots grown stationary and those on a clinostat. We propose a sequence of events in gravitropic stimulation that considers not only the lateral displacement of statoliths, as predicted by the starch-statolith hypothesis, but also its longitudinal motion, together with differential gravisensitivity of mechanotransducing structures along the lower-most longitudinal cell wall.     

Improved bolometric corrections for WR stars

Evolutionary models allow an assignment of both a mass and a luminosity to a Wolf-Rayet (WR) star in a cluster, and hence allow a determination of the Bolometric Correction (B.C.). The B.C.'s derived for WN stars range from –4.0 to –6.0 with the expected trend of larger values (in absolute values) for stars with higher excitation spectra. For WC stars, there is little evidence for a similar trend; most observations presented here are consistent with B.C.=–4.5, as found by Smith and Maeder (1989). The convergence of B.C. values derived from evolutionary and atmospheric models is extremely satisfactory, giving increased confidence in both methods.     

Deriving the spin rate/orientation from the quiescent spacecraft ABRIXAS using optical observations

With the loss of the battery system of ABRIXAS shortly after launch and consequent absence of telemetry, there was urgent need to determine ABRIXAS' spin rate and orientation in order to assess the possibility of re-establishing telemetry during periods of full-Sun orbits. We, therefore, conducted optical and video observations of ABRIXAS passages with a 1-second time resolution, and later simulated the optical appearance of ABRIXAS for several passages based on a three-dimensional model of the reflectivity properties of the 2.5m × 1.8m × 1.2m size-satellite. Here we present the results of the comparison of our grid of light curve models with the observations and show (i) how the spin rate of ABRIXAS slowed down between June and December 1999 and (ii) what information can be deduced on the temporal change of the orientation of the spin axis. We conclude with discussing the benefit of using ground based optical observation as a cost effective way to develop information about the orientation of a satellite when there is no telemetry.     

Inactivation, mutation induction and repair in Bacillus subtilis spores irradiated with heavy ions.

Studies on the response of bacterial spores to accelerated heavy ions (HZE particles) help in understanding problems of space radiobiology and exobiology. Layers of spores of Bacillus subtilis strains, differing in repair capabilities, were irradiated with accelerated boron, carbon and neon ions of linear energy transfer (LET) values up to 14000 MeV cm2/g. Inactivation as measured by loss of colony forming ability and induction of mutations as measured by reversion to histidine prototrophy and resistance to 150 micrograms/ml sodium azide were tested, as well as the influence of repair processes on these effects. For inactivation, the cross-sectional values sigma plotted as a function of LET follow a saturation curve. The plateau, which is reached around a LET of 2000 MeV cm2/g, occurs at 2.5 x 10(-9) cm2, a value in good agreement with the dimensions of the spore protoplast. Lethal damage produced at LET values < 2000 MeV cm2/g is reparable. Recombination repair is more effective than excision repair. At higher LET values, lethal damage could not be reconstituted by the repair mechanisms studied. In addition, at these high LET values, the frequency of induced mutations was drastically decreased. The data support the assumption of at least two qualitatively different types of lesion, depending on the LET of the affecting heavy ion.     

An Optimally Integrated Track Recovery System for Aerial Bathymetry

An airborne system has been developed for charting shallow coastal and inland waters. The primary components of this system are an aerial survey camera, a profiling laser radar, an analytical stereo plotter, and a multisensor track recovery system (TRS). The TRS comprises a gimbaled inertial navigation system and a number of auxiliary sensors which acquire redundant position and attitude information. The sensor data are combined postmission using a U-D factorized Kalman filter and modified Bryson-Frazier smoother to compute accurate estimates of the orientation parameters of the survey camera at the times of film exposure. These parameters are used to position each overlapping pair of photographs on the analytical plotter to form a stereo image and corresonding analytical stereomodel from which water depth measurements are made. Flight trial results demonstrate that the TRS can achieve radial position and attitude accuracies which exceed 1 m and 2 arcmin root mean square (rms), respectively, and that this level of performance is sufficient to enable water depth measurements to be made to an accuracy of better than 0.65 m (rms).