Prolonged weightlessness and calcium loss in man

Data have been accumulated from a series of studies in which men have been subjected to weightlessness in orbital space flight for periods of up to 12 weeks. These data are used to predict the long term consequences of weightlessness upon the skeletal system. Space flight induced a loss of calcium which accelerated exponentially from about 50 mg/d at the end of 1 week to approx. 300 mg/d at the end of 12 weeks. The hypercalciuria reached a constant level within 4 weeks while fecal calcium losses continued to increase throughout the period of exposure. This apparent diminution of gastrointestinal absorptive efficiency was accompanied by a slight decline in the plasma level of parathyroid hormone and a slight elevation in the plasma level of calcium and phosphorus. Although losses in mineral from the calcaneus were closely correlated with the calcium imbalance, no changes were detected in the mineral mass of the ulna and radius. From the data presented it is concluded that the process of demineralization observed in space flight is more severe than would be predicted on the basis of observations in immobilized, bed rested, or paralyzed subjects. It is, moreover, suggested that the process may not be totally reversible.     

Debris swarms seen by SMEI

The large 3° × 60° fields-of-view of the Solar Mass Ejection Imager (SMEI) instruments are oriented on the stabilized Coriolis satellite to image most of the sky each Sun-synchronous orbit. Besides observing coronal mass ejections, the SMEI mission objective, SMEI also has detected a plethora of Earth-orbiting satellites (resident space objects or RSOs) brighter than ∼8th magnitude at a rate of about 1 per minute. Occasionally, SMEI sees an RSO swarm: a sudden onset of a large number of RSOs, many more than the nominal rate, upto dozens detected in a 4-s frame. These swarms usually last for a few minutes. A sample of six such RSO ensembles is analyzed in this paper in which the distance and the direction of the velocity vector for individual objects are estimated. We present the observational evidence indicating that the swarms must be near-field objects traveling in orbits near that of Coriolis, and that the relatively speeds between the objects and Coriolis are low. Further, analyses indicate that the RSOs are quite close (<20 m) and are generally moving radially away from the satellite. The predicted encounter geometries for Coriolis passing through or near a small debris cloud is, generally, quite inconsistent with the observations. The most likely explanation consistent with the observations is that SMEI is seeing debris being ejected from the Coriolis spacecraft itself. An analysis of distance and brightness for a subset of the RSOs indicates that the median diameter of the debris particles is ∼80 μm.     

Performance analysis of a dynamic programming track before detectalgorithm

We analyze a dynamic programming (DP)-based track before detect (TBD) algorithm. By using extreme value theory we obtain explicit expressions for various performance measures of the algorithm such as probability of detection and false alarm. Our analysis has two advantages. First the unrealistic Gaussian and independence assumptions used in previous works are not required. Second, the probability of detection and false alarm curves obtained fit computer simulated performance results significantly more accurately than previously proposed analyses of the TBD algorithm     

ROSAT observations of X-ray sources in globular clusters

We review the first observations of globular clusters obtained with the X-ray telescope on board of the ROSAT satellite. In the All-Sky Survey, all known bright sources and two new transient sources were detected. In addition a super-soft source was found in NGC5272. Concerning the dim sources, the survey suggests that those outside the core of ω Cen are not related to the cluster. The survey further improved by one or two magnitudes on many upper limits previously obtained by the HEAO-1 satellite. Pointed observations have improved the positional accuracy of a number of sources, and added to the number of known dim sources. In 47 Tuc, the known central source is resolved into 4 separate sources, which we argue are all soft X-ray transients. A comparison with observations of the old open cluster M67 leads us to suggest that some of the dim sources may be conglomerates of a large number of RS Can Ven type binaries.     

Radar Literature Sources

This correspondence presents information on radar literature sources to augment the International Cumulative Index on Radar Systems[1]. The purpose is to provide information on languages and translations of some technical journals and to give additional journals with sources of abstracts of engineering reports and patents on radar.     

The Solar Mass Ejection Imager and Its Heliospheric Imaging Legacy

The Solar Mass Ejection Imager (SMEI) was the first of a new class of heliospheric and astronomical white-light imager. A heliospheric imager operates in a fashion similar to coronagraphs, in that it observes solar photospheric white light that has been Thomson scattered by free electrons in the solar wind plasma. Compared with traditional coronagraphs, this imager differs in that it observes at much larger angles from the Sun. This in turn requires a much higher sensitivity and wider dynamic range for the measured intensity. SMEI was launched on the Coriolis spacecraft in January 2003 and was deactivated in September 2011, thus operating almost continuously for nearly nine years. Its primary objective was the observation of interplanetary transients, typically coronal mass ejections (CMEs), and tracking them continuously throughout the inner heliosphere. Towards this goal it was immediately effective, observing and tracking several CMEs in the first month of mission operations, with some 400 detections to follow. Along with this primary science objective, SMEI also contributed to many and varied scientific fields, including studies of corotating interaction regions (CIRs), the high-altitude aurora, zodiacal light, Gegenschein, comet tail disconnections and motions, and variable stars. It was also able to detect and track Earth-orbiting satellites and space debris. Along with its scientific advancements, SMEI also demonstrated a significantly improved accuracy of space weather prediction, thereby establishing the feasibility and usefulness of operational heliospheric imagers. In this paper we review the scientific and operational achievements of SMEI, discuss lessons learned, and present our view of potential next steps in future heliospheric imaging.     

AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment

The radiation belts and plasma in the Earth’s magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper.