Influence of gravity on the circadian timing system.

The circadian timing system (CTS) is responsible for daily temporal coordination of physiological and behavioral functions both internally and with the external environment. Experiments in altered gravitational environments have revealed changes in circadian rhythms of species ranging from fungi to primates. The altered gravitational environments examined included both the microgravity environment of spaceflight and hyperdynamic environments produced by centrifugation. Acute exposure to altered gravitational environments changed homeostatic parameters such as body temperature. These changes were time of day dependent. Exposure to gravitational alterations of relatively short duration produced changes in both the homeostatic level and the amplitude of circadian rhythms. Chronic exposure to a non-earth level of gravity resulted in changes in the period of the expressed rhythms as well as in the phase relationships between the rhythms and between the rhythms and the external environment. In addition, alterations in gravity appeared to act as a time cue for the CTS. Altered gravity also affected the sensitivity of the pacemaker to other aspects of the environment (i.e., light) and to shifts of time cues. Taken together, these studies lead to the conclusion that the CTS is indeed sensitive to gravity and its alterations. This finding has implications for both basic biology and space medicine.     

Future of Space Astronomy: A global Road Map for the next decades

The use of space techniques continues to play a key role in the advance of astrophysics by providing access to the entire electromagnetic spectrum from radio to high energy γ rays. The increasing size, complexity and cost of large space observatories places a growing emphasis on international collaboration. Furthermore, combining existing and future datasets from space and “ground based” observatories is an emerging mode of powerful and relatively inexpensive research to address problems that can only be tackled by the application of large multi-wavelength observations. While the present set of astronomical facilities is impressive and covers the entire electromagnetic spectrum, with complementary space and “ground based” telescopes, the situation in the next 10–20 years is of critical concern. The James Webb Space Telescope (JWST), to be launched not earlier than 2018, is the only approved future major space astronomy mission. Other major highly recommended space astronomy missions, such as the Wide-field Infrared Survey Telescope (WFIRST), the International X-ray Observatory (IXO), Large Interferometer Space Antenna (LISA) and the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), have yet to be approved for development.     

Microwave Azimuth Measuring System

A breadboard microwave pointing device (ElectroTransit) has been designed, fabricated, and tested. The device and accompanying RF sources comprise a portable, battery-operated, azimuth angle measuring system with application in surveying, mapping, and geodesy, and for conducting basic research in tropospheric propagation and turbulence studies. The angle measuring sensor combines a Ka-band interferometer with an optical theodolite to provide two modes of pointing. Azimuth angle can be read directly to 0.1 arc-second. Preliminary tests on the interferometer show a pointing repeatability on the order of two arc-seconds, three sigma, when tropospheric turbulence is minimum and a mean absolute error of less than 10 arc-seconds, three sigma, compared with first-order optical standards. This paper describes the design, fabrication, and testing of this extremely precise instrumentation.     

United States space policy and international partnership

Has the current US space policy improved the USA's overall strategic position? Does it affect favorably international partnerships? These questions are examined in terms of security, political economy, and influence. In today's context, where there are more space players, more options, more potential for unintended consequences, and higher stakes, unilateral action is more limited in its effectiveness than in earlier times. Surveying current US space policy, it is not clear that data-driven, analytically based decisions are being made to affect positively national independence, innovation, market creation, and international perceptions of the USA as a trustworthy partner. More promising are the steps taken to bolster a predictable space operational environment and economic competitiveness. Ultimately, in order to achieve American excellence and leadership, a ‘closed loop’ on the policy system is needed, to gauge regularly and systematically whether the US is achieving the desired national outcomes.     

MMAE/MMAC control for bending with multiple uncertain parameters

A moving-bank multiple model estimator/controller (MMAE/MMAC) based on linear system, quadratic cost, and Gaussian noise (LQG) assumptions is used to quell unwanted vibrations in a simulated large flexible space structure. The structure, known as the Space Integrated Controls Experiment (SPICE), exists at Phillips Laboratory, Kirtland Air Force Base, New Mexico. The structure consists of a large platform and a smaller platform connected by a tripod of flexible legs. The purpose of the control system is to maintain a very precise line-of-sight (LOS) vector through the center of the spacecraft. Kalman filtering, used to estimate the position and velocity of the bending modes of the structure, and LQG control techniques are the primary design tools used in the MMAE/MMAC algorithms. Implementing a parallel bank of filters increases robustness when uncertainties exist in the system model, here specifically allowing adaptation to uncertain and changing undamped natural frequencies of the bending modes of the structure. A moving-bank algorithm is utilized to reduce the computational loading. The MMAE/MMAC design provides a well-suited method of estimating variations in the vector of undamped natural frequencies and quelling vibrations in the structure. The MMAE/MMAC was able to track numerous parameter changes and jumps while providing adequate control for the structure.     

Supraglacial sulfur springs and associated biological activity in the Canadian high arctic-signs of life beneath the ice

Unique springs, discharging from the surface of an arctic glacier, release H(2)S and deposit native sulfur, gypsum, and calcite. The presence of sulfur in three oxidation states indicates a complex series of redox reactions. Physical and chemical conditions of the spring water and surrounding environment, as well as mineralogical and isotopic signatures, suggest biologically mediated reactions. Cell counts and DNA analyses confirm bacteria are present in the spring system, and a limited number of sequenced isolates suggests that complex communities of bacteria live within the glacial system.     

The BOOMERANG experiment

The BOOMERANG (Balloon Observations Of Millimetric Extragalactic RAdiation aNd Geophysics) experiment is an international effort to measure the Cosmic Microwave Background (CMB) anisotropy on angular scales of 20 to 4°, with unprecedented sensitivity, sky and spectral coverage. The telescope will be flown from Antarctica by NASA-NSBF with a long duration stratospheric balloon (7–14 days), and is presently scheduled for flight in 1995–1996. The experiment is designed to produce an image of the Cosmic Microwave Background with high sensitivity and large sky coverage. These data will tightly constrain the baryon density, the reionization history, and the formation of large-scale structure in the universe. BOOMERANG will test technologies and return science data that are essential to the design of a future space-borne mission to map CMB anisotropy.