Independent validation and verification of the TCAS II collisionavoidance subsystem

This paper describes the specification-based testing, analysis tools, and associated processes used to independently validate, verify, and ultimately, provide for certifying safety-critical software developed for the Traffic Alert and Collision Avoidance System (TCAS II) program. These tools and processes comprise an effective and Independent Validation and Verification (IV and V) activity applied to the Collision Avoidance Subsystem (GAS) software development process. A requirements specification language called the Requirements State Machine Language (RSML), originally developed by the University of California, Irvine (UCI), was employed for the specification of GAS. The end result is the next generation of TCAS II collision avoidance logic, referred to as Version 7, that is of a higher quality than its predecessors, meets the certification requirements of DO-178B Level B (Ref. 1), and can be shown to satisfy the new operational requirements it was developed to address     

Large-scale Coronal Heating, Clustering of Coronal Bright Points, and Concentration of Magnetic Flux

By combining quiet-region Fe XII coronal images from SOHO/EIT with magnetograms from NSO/Kitt Peak and from SOHO/MDI, we show that the population of network coronal bright points and the magnetic flux content of the network are both markedly greater under the bright half of the large-scale quiet corona than under the dim half. These results (1) support the view that the heating of the entire corona in quiet regions and coronal holes is driven by fine-scale magnetic activity (microflares, explosive events, spicules) seated low in the magnetic network, and (2) suggest that this large-scale modulation of the magnetic flux and coronal heating is a signature of giant convection cells. This revised version was published online in June 2006 with corrections to the Cover Date.     

Antideuterons as an indirect dark matter signature: Si(Li) detector development and a GAPS balloon mission

The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. GAPS complements existing and planned direct dark matter searches as well as other indirect techniques, probing a different and unique region of parameter space in a variety of proposed dark matter models. The GAPS method involves capturing antiparticles into a target material with the subsequent formation of an excited exotic atom. The exotic atom decays with the emission of atomic X-rays and pions from the nuclear annihilation, which uniquely identifies the captured antiparticle. This technique has been verified through the accelerator testing at KEK in 2004 and 2005. The prototype flight is scheduled from Hokkaido, Japan in 2011, preparatory for a long duration balloon flight from the Antarctic in 2014.     

Long period magnetospheric oscillations at discrete frequencies: The results of a multi-station analysis

A multi-station analysis of geomagnetic field measurements conducted for a remarkable case event, at a European and an American array shows that, although several aspects of the geomagnetic field observations show a clear latitudinal and local time dependence, simultaneous oscillations at discrete frequencies (f ≈ 1.0, 1.3, 2.2 and 3.2 mHz) are almost ubiquitously detected, from low to high latitudes both in the light and dark sector. They are driven by fluctuations of the solar wind density and dynamic pressure at the same frequencies, via the modulation of the magnetopause current. We also report clear evidence for the occurrence of resonant coupling (at f ≈ 2.2 and 3.2 mHz) between such modes and high latitude field lines. Due to the variable length of the field line through the day, oscillation modes at the same frequencies resonate at different latitudes in the daytime and nighttime region, respectively.     

Energy Release and Particle Acceleration in Flares: Summary and Future Prospects

RHESSI measurements relevant to the fundamental processes of energy release and particle acceleration in flares are summarized. RHESSI??s precise measurements of hard X-ray continuum spectra enable model-independent deconvolution to obtain the parent electron spectrum. Taking into account the effects of albedo, these show that the low energy cut-off to the electron power-law spectrum is typically ?tens of keV, confirming that the accelerated electrons contain a large fraction of the energy released in flares. RHESSI has detected a high coronal hard X-ray source that is filled with accelerated electrons whose energy density is comparable to the magnetic-field energy density. This suggests an efficient conversion of energy, previously stored in the magnetic field, into the bulk acceleration of electrons. A new, collisionless (Hall) magnetic reconnection process has been identified through theory and simulations, and directly observed in space and in the laboratory; it should occur in the solar corona as well, with a reconnection rate fast enough for the energy release in flares. The reconnection process could result in the formation of multiple elongated magnetic islands, that then collapse to bulk-accelerate the electrons, rapidly enough to produce the observed hard X-ray emissions. RHESSI??s pioneering ??-ray line imaging of energetic ions, revealing footpoints straddling a flare loop arcade, has provided strong evidence that ion acceleration is also related to magnetic reconnection. Flare particle acceleration is shown to have a close relationship to impulsive Solar Energetic Particle (SEP) events observed in the interplanetary medium, and also to both fast coronal mass ejections and gradual SEP events. New instrumentation to provide the high sensitivity and wide dynamic range hard X-ray and ??-ray measurements, plus energetic neutral atom (ENA) imaging of SEPs above ??2 R_??, will enable the next great leap forward in understanding particle acceleration and energy release is large solar eruptions??solar flares and associated fast coronal mass ejections (CMEs).     

The Education and Public Outreach Program for NASA��s Dawn Mission

The Dawn mission??s Education and Public Outreach (E/PO) program takes advantage of the length of the mission, an effort to maintain level funding, and the exceptional support of the science and engineering teams to create formal and informal educational materials that bring STEM content and modes of thinking to students of all ages. With materials that are based on researched pedagogical principles and aligned with science education standards, Dawn weaves together many aspects of the mission to engage students, teachers, and the general public. E/PO tells the story of the discovery of the asteroid belt, uncovers principles of physics behind the ion propulsion that powers the spacecraft, and explains what we can learn from the instrumentation and how the mission??s results will expand our understanding of the origins of the solar system. In this way, we not only educate and inform, we build anticipation and expectation in the general public for the spacecraft??s arrival at Vesta in 2011 and three years later at Ceres. This chapter discusses the organization, strategies, formative assessment and dissemination of these materials and activities, and includes a section on lessons learned.     

Dawn Science Planning, Operations and Archiving

The Dawn science operations team has designed the Vesta mission within the constraints of a low-cost Discovery mission, and will apply the same methodology to the Ceres mission. The design employs proactive mapping mission strategies and tactics such as functional redundancy, adaptability to trajectory uncertainties, and easy sequence updates to deliver reliable and robust sequences. Planning tools include the Science Opportunity Analyzer and other multi-mission tools, and the Science time-ordered listings. Science operations are conducted jointly by the Science Operations Support Team at the Jet Propulsion Laboratory (JPL) and the Dawn Science Center at the University of California, Los Angeles (UCLA). The UCLA Dawn Science Center has primary responsibility for data archiving while the JPL team has primary responsibility for spacecraft and instrument operations. Constraints and uncertainties in the planning and sequencing environment are described, and then details of the science plan are presented for each mission sub-phase. The plans indicate that Dawn has a high probability of meeting its science objectives and requirements within the imposed constraints.     

A DORIS determination of the absolute velocities of the Sorsdal and Mellor glaciers in Antarctica

The Lambert–Amery System is the largest glacier–ice shelf system in East Antarctica, draining a significant portion of the ice sheet. Variation in ice sheet discharge from Antarctica or Greenland has an impact on the rate of change in global mean sea level; which is a manifestation of climate change. In conjunction with a measure of ice thickness change, ice sheet discharge can be monitored by determining the absolute velocities of these glaciers.