Preface

Journal of Reducing Space Mission Cost -     

Be stars in young clusters in the Magellanic Clouds

A substantial fraction (typically 10%) of Galactic B stars consists of Be stars. While Galactic Be stars have been fairly well investigated, very little is known about the Be star content of the Magellanic Clouds (MCs). We present a refined method of Be star identification by CCD photometry and apply it to four young clusters and associations in the MCs. We find NGC 330 in the SMC to be exceptionally rich in Be stars, while the fraction is clearly lower in the similarly aged LMC clusters NGC 2004 and NGC 1818. NGC 2044, a very young region in the LMC, contains almost no Be stars. Among very early-type B stars in the investigated MC clusters we find the largest number of Be stars, while in the Milky Way this is shifted to somewhat later types. In the LMC, there may be a second frequency peak around B6.Based on observations obtained at the 2.2m MPIA telescope at ESO, La Silla, Chile, partly on time granted by the MPIA, Heidelberg.     

Effects of heavy particle irradiation and diet on object recognition memory in rats

On long-duration missions to other planets astronauts will be exposed to types and doses of radiation that are not experienced in low earth orbit. Previous research using a ground-based model for exposure to cosmic rays has shown that exposure to heavy particles, such as ⁵⁶Fe, disrupts spatial learning and memory measured using the Morris water maze. Maintaining rats on diets containing antioxidant phytochemicals for 2 weeks prior to irradiation ameliorated this deficit. The present experiments were designed to determine: (1) the generality of the particle-induced disruption of memory by examining the effects of exposure to ⁵⁶Fe particles on object recognition memory; and (2) whether maintaining rats on these antioxidant diets for 2 weeks prior to irradiation would also ameliorate any potential deficit. The results showed that exposure to low doses of ⁵⁶Fe particles does disrupt recognition memory and that maintaining rats on antioxidant diets containing blueberry and strawberry extract for only 2 weeks was effective in ameliorating the disruptive effects of irradiation. The results are discussed in terms of the mechanisms by which exposure to these particles may produce effects on neurocognitive performance.     

The Science Case for STEP

The Satellite Test of the Equivalence Principle (STEP) will advance experimental limits on violations of Einstein’s Equivalence Principle (EP) from their present sensitivity of 2 parts in 10¹³${10}^{13}$ to 1 part in 10¹⁸${10}^{18}$ through multiple comparison of the motions of four pairs of test masses of different compositions in an earth-orbiting drag-free satellite. Dimensional arguments suggest that violations, if they exist, should be found in this range, and they are also suggested by leading attempts at unified theories of fundamental interactions (e.g., string theory) and cosmological theories involving dynamical dark energy. Discovery of a violation would constitute the discovery of a new force of nature and provide a critical signpost toward unification. A null result would be just as profound, because it would close off any possibility of a natural-strength coupling between standard-model fields and the new light degrees of freedom that such theories generically predict (e.g., dilatons, moduli, quintessence). STEP should thus be seen as the intermediate-scale component of an integrated strategy for fundamental physics experiments that already includes particle accelerators (at the smallest scales) and supernova probes (at the largest). The former may find indirect evidence for new fields via their missing-energy signatures, and the latter may produce direct evidence through changes in cosmological equation of state—but only a gravitational experiment like STEP can go further and reveal how or whether such a field couples to the rest of the standard model. It is at once complementary to the other two kinds of tests, and a uniquely powerful probe of fundamental physics in its own right.     

Advances in Plasmaspheric Wave Research with CLUSTER and IMAGE Observations

This paper highlights significant advances in plasmaspheric wave research with Cluster and Image observations. This leap forward was made possible thanks to the new observational capabilities of these space missions. On one hand, the multipoint view of the four Cluster satellites, a unique capability, has enabled the estimation of wave characteristics impossible to derive from single spacecraft measurements. On the other hand, the Image experiments have enabled to relate large-scale plasmaspheric density structures with wave observations and provide radio soundings of the plasmasphere with unprecedented details. After a brief introduction on Cluster and Image wave instrumentation, a series of sections, each dedicated to a specific type of plasmaspheric wave, put into context the recent advances obtained by these two revolutionary missions.     

Interplanetary Coronal Mass Ejections Observed in the Heliosphere: 1. Review of Theory

With the recent advancements in interplanetary coronal mass ejection (ICME) imaging it is necessary to understand how heliospheric images may be interpreted, particularly at large elongation angles. Of crucial importance is how the current methods used for coronal mass ejection measurement in coronagraph images must be changed to account for the large elongations involved in the heliosphere. In this review of theory we build up a picture of ICME appearance and evolution at large elongations in terms of how it would appear to an observer near 1 AU from the Sun. We begin by revisiting the basics of Thomson scattering describing how ICMEs are detected, in this we attempt to clarify a number of common misconceptions. We then build up from a single electron to an integrated line of sight, consider the ICME as a collection of lines of sight and describe how a map of ICME appearance may be developed based on its appearance relative to each line of sight. Finally, we discuss how the topology of the ICME affects its observed geometry and kinematic properties, particularly at large elongations. This review is the first of a three-part series of papers, where a review of theory is presented here and a model is developed and used in subsequent papers.     

Development of a thin section device for space exploration: Overview and system performance estimates

In this paper we present a conceptual design of a spaceborne instrument for the in situ production of rock thin sections on planetary surfaces. The in situ Automated Rock Thin Section Instrument (IS-ARTS) conceptual design demonstrates that the in situ production of thin sections on a planetary body is a plausible new instrument capability for future planetary exploration. Thin section analysis would reduce much ambiguity in the geological history of a sampled site that is present with instruments currently flown. The technical challenge of producing a thin section device compatible with the spacecraft environment is formidable and has been thought too technically difficult to be practical. Terrestrial thin section preparation requires a skilled petrographist, several preparation instruments that individually exceed typical spacecraft mass and power limits, and consumable materials that are not easily compatible with spaceflight. In two companion papers we present research and development work used to constrain the capabilities of IS-ARTS in the technical space compatible with the spacecraft environment. For the design configuration shown we conclude that a device can be constructed that is capable of 50 sample preparations over a 2 year lifespan with mass, power, and volume constraints compatible with current landed Mars mission configurations. The technical requirements of IS-ARTS (mass, power and number of samples produced) depend strongly on the sample mechanical properties, sample processing rate, the sample size and number of samples to be produced.     

Interplanetary Coronal Mass Ejections Observed in the Heliosphere: 3. Physical Implications

We conclude the heliospheric image series with this third and final instalment, where we consider the physical implications of our reconstruction of interplanetary coronal mass ejections from heliospheric imagers. In Paper 1 a review of the theoretical framework for the appearance of ICMEs in the heliosphere was presented and in Paper 2 a model was developed that extracted the three-dimensional structure and kinematics of interplanetary coronal mass ejections directly from SMEI images. Here we extend the model to include STEREO Heliospheric Imager data and reproduce the three-dimensional structure and kinematic evolution of a single Earth-directed interplanetary coronal mass ejection that was observed in November 2007. These measurements were made with each spacecraft independently using leading edge measurements obtained from each instrument. We found that when data from the three instruments was treated as a single collective, we were able to reproduce an estimate of the ICME structure and trajectory. There were some disparities between the modelled ICME and the in situ data, and we interpret this as a combination of a slightly more than spherically curved ICME structure and a corotating interaction region brought about by the creation of a coronal hole from the CME eruption. This is the first time evidence for such a structure has been presented and we believe that it is likely that many ICMEs are of this nature.     

Development of a thin section device for space exploration: Rock cutting mechanism

We have developed a rock cutting mechanism for in situ planetary exploration based on abrasive diamond impregnated wire. Performance characteristics of the rock cutter, including cutting rate on several rock types, cutting surface lifetime, and cut rock surface finish are presented. The rock cutter was developed as part of a broader effort to develop an in situ automated rock thin section (IS-ARTS) instrument. The objective of IS-ARTS was to develop an instrument capable of producing petrographic rock thin sections on a planetary science spacecraft. The rock cutting mechanism may also be useful to other planetary science missions with in situ instruments in which sub-sampling and rock surface preparation are necessary.