The low-energy neutral atom imager for IMAGE

The `Imager for Magnetosphere-to-Aurora Global Exploration (IMAGE) will be launched early in the year 2000. It will be the first mission dedicated to imaging, with the capability to determine how the magnetosphere changes globally in response to solar storm effects in the solar wind, on time scales as short as a few minutes. The low energy neutral atom (LENA) imager uses a new atom-to-negative ion surface conversion technology to image the neutral atom flux and measure its composition (H and O) and energy distribution (10 to 750 eV). LENA uses electrostatic optics techniques for energy (per charge) discrimination and carbon foil time-of-flight techniques for mass discrimination. It has a 90°×° field-of-view in 12 pixels, each nominally 8°×°. Spacecraft spin provides a total field-of-view of 90°×360°, comprised of 12×45 pixels. LENA is designed to image fast neutral atom fluxes in its energy range, emitted by auroral ionospheres or the sun, or penetrating from the interstellar medium. It will thereby determine how superthermal plasma heating is distributed in space, how and why it varies on short time scales, and how this heating is driven by solar activity as reflected in solar wind conditions.     

The OSIRIS-REx Laser Altimeter (OLA) Investigation and Instrument

Space Science Reviews - The Canadian Space Agency (CSA) has contributed to the Origins Spectral Interpretation Resource Identification Security-Regolith Explorer (OSIRIS-REx) spacecraft the...     

A sensitivity study of the effectiveness of active debris removal in LEO

The near-Earth orbital debris population will continue to increase in the future due to ongoing space activities, on-orbit explosions, and accidental collisions among resident space objects. Commonly adopted mitigation measures, such as limiting postmission orbital lifetimes of satellites to less than 25 years, will slow down the population growth, but will be insufficient to stabilize the environment. To better limit the growth of the future debris population, the remediation option, i.e., removing existing large and massive objects from orbit, needs to be considered. This paper does not intend to address the technical or economical issues for active debris removal. Rather, the objective is to provide a sensitivity study to illustrate and quantify the effectiveness of various remediation options. An effective removal criterion based upon mass and collision probability is developed. This study includes simulations with removal rates ranging from 5 to 20 objects per year, starting in the year 2020. The outcome of each simulation is analyzed and compared with others. The summary of the study serves as a general guideline for future debris removal consideration.     

An endogenous growth pattern of roots is revealed in seedlings grown in microgravity

In plants, sensitive and selective mechanisms have evolved to perceive and respond to light and gravity. We investigated the effects of microgravity on the growth and development of Arabidopsis thaliana (ecotype Landsberg) in a spaceflight experiment. These studies were performed with the Biological Research in Canisters (BRIC) hardware system in the middeck region of the space shuttle during mission STS-131 in April 2010. Seedlings were grown on nutrient agar in Petri dishes in BRIC hardware under dark conditions and then fixed in flight with paraformaldehyde, glutaraldehyde, or RNAlater. Although the long-term objective was to study the role of the actin cytoskeleton in gravity perception, in this article we focus on the analysis of morphology of seedlings that developed in microgravity. While previous spaceflight studies noted deleterious morphological effects due to the accumulation of ethylene gas, no such effects were observed in seedlings grown with the BRIC system. Seed germination was 89% in the spaceflight experiment and 91% in the ground control, and seedlings grew equally well in both conditions. However, roots of space-grown seedlings exhibited a significant difference (compared to the ground controls) in overall growth patterns in that they skewed to one direction. In addition, a greater number of adventitious roots formed from the axis of the hypocotyls in the flight-grown plants. Our hypothesis is that an endogenous response in plants causes the roots to skew and that this default growth response is largely masked by the normal 1?g conditions on Earth.     

Soviet year in space, 1989

The euphoria surrounding the maiden voyage of the Buran space shuttle seemed to evaporate in 1989, and the Soviet space programme entered a critical period of re-evaluation and self-criticism. Setbacks dogged the Mir, Phobos and other programmes, though there did not appear to be a launch failure throughout the year. Public debate was dominated by economic issues, though useful figures are hard to obtain.     

Comparative analysis of energy storage media and techniques

Techniques for storing and converting energy from one form to another are examined. The parameters of interest are storage density (in terms of both energy and power), conversion efficiency, and number of steps in the conversion process. The techniques compared are electrostatic, magnetic, inertial, chemical, thermal, and nuclear. Each technique for storage is discussed in terms of the ease with which the energy can be converted to electricity for powering lightweight compact power systems for a variety of uses. The storage density associated with the various mechanisms spans an enormous range (~0.5 MJ/kg to ~10⁵ MJ/kg). The impact upon time-to-refuel within the context of mobile tactical army applications is discussed     

HF multipath passive single site radio location

This paper considers the problem of passive geolocation for the case of HF multipath propagation. A new technique is developed for the estimation of interpath time delay applying the multiple signal classification (MUSIC) superresolution spectral estimation method. The technique samples the signals received by two spatially separated antennas to compute the normalized MUSIC cepstrum. The method is applied to experimental data in a preliminary proof-of-concept analysis     

A mathematical and experimental simulation of the hematological response to weightlessness

Two ground-based methods of weightlessness simulation--a computer model of erythropoiesis feedback regulation and bedrest--were used to investigate the mechanisms which lead to loss of red cell mass during spaceflight. Both methods were used to simulate the first Skylab mission of 28 days. Human bedrest subjects lose red cell mass linearly with time and in this study the loss was 6.7% at the end of four weeks (compared to 14% in Skylab). Postbedrest recovery of red cell mass was delayed for two weeks during which time a further decline in this quantity was noted. This is consistent with the first Skylab mission but not with the two longer flights of two and three months. Hemoconcentration, observed early in the study, was essentially maintained despite red cell loss because of continued loss of plasma volume. The computer model, using the time-varying hematocrit data to estimate red cell production rates, predicted dynamic behavior of plasma volume and red cell mass that was in close agreement with the measured values. The results support the hypothesis that red cell loss during supine bedrest is a normal physiological feedback process in response to hemoconcentration enhanced tissue oxygenation and suppression of red cell production. In contrast, the delayed postbedrest recovery of red cell mass was more difficult to explain, especially in the light of enhanced reticulocyte indices observed at the onset on ambulation. Model simulation suggested the possibilities, still to be experimentally demonstrated, that this period was marked by some combination of increased oxygen-hemoglobin affinity, small reductions in mean red cell life span, ineffective erythropoiesis, or abnormal reticulocytosis. The question of whether hemoconcentration is the sole contributor to spaceflight red cell losses also remains to be resolved.     

On orbit fabrication and assembly of large space structural subsystems

The evolving use of large space systems, with accompanying large truss-like structures, creates the need to develop an on-orbit fabrication and assembly capability for producing structural elements and structural subsystems. Such a capability is a basic necessity for extremely large structural subsystems because of the economy of operations resulting from the on-orbit conversion of high-density material stock into low-density structural elements. This paper discusses the development of large space structural subsystems; in particular the role a generic structure plays in that development. This generic structure embodies the key issues of the structural subsystems of various classes of large space systems and as such, when its development is completed a proof-of-capability will have been accomplished for a wide variety of large space structures.