The Surface Composition of Ceres

Our understanding of the composition of Ceres is driven by remote sensing of its surface. We review spectral observations of Ceres over wavelengths from the ultraviolet to the radio, as well as non-spectral data such as thermal inertia, photometric properties, radar experiments, and surface variability. We also discuss the closest likely meteorite analogs to Ceres and consider the likelihood that material from Ceres could be delivered to Earth.     

On the Differences in Composition between Solar Energetic Particles and Solar Wind

Although the average composition of solar energetic particles (SEPs) and the bulk solar wind are similar in a number of ways, there are key differences which imply that solar wind is not the principal seed population for SEPs accelerated by coronal mass ejection (CME) driven shocks. This paper reviews these composition differences and considers the composition of other possible seed populations, including coronal material, impulsive flare material, and interplanetary CME material.     

Variability of spectra in large solar energeticparticle events

Using data from the Solar Isotope Spectrometer on the Advanced Composition Explorer obtained during 36large solar energetic particle events (SEPs) that occurred during 1997–2002 we have examined the spectral characteristics of oxygen and iron. Based on the shape of the oxygen spectrum during the decay phase following the peak in particle intensity, each SEP event was categorized as either exponential (7 events) or power law (29 events). We find that the exponential events were typically the larger events (in terms of peak oxygen intensity) and had Fe/0 ratios that strongly decreased with increasing energy.Event-averaged Fe/0 ratios (integrated over 12 to 60 MeV/nucleon) were at or below coronal abundances for nearly all these events, while the ratios obtained in the power law events were typically enhanced over coronal values. The majority of the power law events had the same spectral index for both 0 and Fe resulting in an Fe/0 ratio independent of energy. However 6 of the 29 power law events had Fe/0 ratios that increased with increasing energy due to an Fe spectral index less negative than that of 0. We consider simple diffusion theory in an effort to understand the nature of these events and obtain preliminary but promising results.     

Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission

The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA’s first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.     

The Low-Energy Telescope (LET) and SEP Central Electronics for the STEREO Mission

The Low-Energy Telescope (LET) is one of four sensors that make up the Solar Energetic Particle (SEP) instrument of the IMPACT investigation for NASA’s STEREO mission. The LET is designed to measure the elemental composition, energy spectra, angular distributions, and arrival times of H to Ni ions over the energy range from ～3 to ～30 MeV/nucleon. It will also identify the rare isotope ³He and trans-iron nuclei with 30≤Z≤83. The SEP measurements from the two STEREO spacecraft will be combined with data from ACE and other 1-AU spacecraft to provide multipoint investigations of the energetic particles that result from interplanetary shocks driven by coronal mass ejections (CMEs) and from solar flare events. The multipoint in situ observations of SEPs and solar-wind plasma will complement STEREO images of CMEs in order to investigate their role in space weather. Each LET instrument includes a sensor system made up of an array of 14 solid-state detectors composed of 54 segments that are individually analyzed by custom Pulse Height Analysis System Integrated Circuits (PHASICs). The signals from four PHASIC chips in each LET are used by a Minimal Instruction Set Computer (MISC) to provide onboard particle identification of a dozen species in ～12 energy intervals at event rates of ～1,000 events/sec. An additional control unit, called SEP Central, gathers data from the four SEP sensors, controls the SEP bias supply, and manages the interfaces to the sensors and the SEP interface to the Instrument Data Processing Unit (IDPU). This article outlines the scientific objectives that LET will address, describes the design and operation of LET and the SEP Central electronics, and discusses the data products that will result.     

Energy Spectra, Composition, and Other Properties of Ground-Level Events During Solar Cycle 23

We report spacecraft measurements of the energy spectra of solar protons and other solar energetic particle properties during the 16 Ground Level Events (GLEs) of Solar Cycle 23. The measurements were made by eight instruments on the ACE, GOES, SAMPEX, and STEREO spacecraft and extend from ～0.1 to ～500–700?MeV. All of the proton spectra exhibit spectral breaks at energies ranging from ～2 to ～46?MeV and all are well fit by a double power-law shape. A comparison of GLE events with a larger sample of other solar energetic particle (SEP) events shows that the typical spectral indices are harder in GLE events, with a mean slope of ?3.18 at >40?MeV/nuc. In the energy range 45 to 80?MeV/nucleon about ～50?% of GLE events have properties in common with impulsive ³He-rich SEP events, including enrichments in Ne/O, Fe/O, ²²Ne/²⁰Ne, and elevated mean charge states of Fe. These ³He-rich events contribute to the seed population accelerated by CME-driven shocks. An analysis is presented of whether highly-ionized Fe ions observed in five events could be due to electron stripping during shock acceleration in the low corona. Making use of stripping calculations by others and a coronal density model, we can account for events with mean Fe charge states of 〈Q _Fe〉≈+20 if the acceleration starts at ～1.24–1.6 solar radii, consistent with recent comparisons of CME trajectories and type-II radio bursts. In addition, we suggest that gradual stripping of remnant ions from earlier large SEP events may also contribute a highly-ionized suprathermal seed population. We also discuss how observed SEP spectral slopes relate to the energetics of particle acceleration in GLE and other large SEP events.     

Evaluation of three ATE test environments

It is often difficult to assess the positive and negative issues facing the use of a particular software test environment in a given application. Much of the literature is swayed by the use of each environment by a single application. This paper will provide detailed information on ARGO Systems evaluation of three popular ATE Test Environments: the Ada Based Environment for Testing (ABET), the TYX PAWS ATLAS test environment and the National Instruments LabVIEW graphical test environment. This evaluation was accomplished by comparing the same test program measurements in each environment using the same UUT, interface test adapter, and the same PC-based ATE. As such, the data represents a true apples-to-apples comparison of these environments     

Preliminary application of a novel algorithm to monitor changes in pre-flight total peripheral resistance for prediction of post-flight orthostatic intolerance in astronauts

Orthostatic intolerance (OI) is a significant challenge for astronauts after long-duration spaceflight. Depending on flight duration, 20–80% of astronauts suffer from post-flight OI, which is associated with reduced vascular resistance. This paper introduces a novel algorithm for continuously monitoring changes in total peripheral resistance (TPR) by processing the peripheral arterial blood pressure (ABP). To validate, we applied our novel mathematical algorithm to the pre-flight ABP data previously recorded from twelve astronauts ten days before launch. The TPR changes were calculated by our algorithm and compared with the TPR value estimated using cardiac output/heart rate before and after phenylephrine administration. The astronauts in the post-flight presyncopal group had lower pre-flight TPR changes (1.66 times) than those in the non-presyncopal group (2.15 times). The trend in TPR changes calculated with our algorithm agreed with the TPR trend calculated using measured cardiac output in the previous study. Further data collection and algorithm refinement are needed for pre-flight detection of OI and monitoring of continuous TPR by analysis of peripheral arterial blood pressure.