Eric Edward Dors

Genesis On-board Determination of the Solar Wind Flow Regime

Some of the objectives of the Genesis mission require the separate collection of solar wind originating in different types of solar sources. Measurements of the solar wind protons, alpha particles, and electrons are used on-board the spacecraft to determine whether the solar-wind source is most likely a coronal hole, interstream flow, or a coronal mass ejection. A simple fuzzy logic scheme operating on measurements of the proton temperature, the alpha-particle abundance, and the presence of bidirectional streaming of suprathermal electrons was developed for this purpose. Additional requirements on the algorithm include the ability to identify the passage of forward shocks, reasonable levels of hysteresis and persistence, and the ability to modify the algorithm by changes in stored constants rather than changes in the software. After a few minor adjustments, the algorithm performed well during the initial portion of the mission.

Comparison Of The Genesis Solar Wind Regime Algorithm Results With Solar Wind Composition Observed By ACE

Launched on 8 August 2001, the NASA Genesis mission is now collecting samples of the solar wind in various materials, and will return those samples to Earth in 2004 for analysis. A primary science goal of Genesis is the determination of the isotopic and elemental composition of the solar atmosphere from the solar wind material returned. In particular, Genesis will provide measurements of those species that are not provided by solar and in situ observations. We know from in situ measurements that the solar wind exhibits compositional variations across different types of solar wind flows. Therefore, Genesis exposes different collectors to solar wind originating from three flow types: coronal hole, coronal mass ejection (CME), and interstream flows. Flow types are identified using in situ measurements of solar wind protons, alphas, and electrons from electrostatic analyzers carried by Genesis. The flow regime selection algorithm and subsequent collector deployment on Genesis act autonomously. We present an assessment of composition variations of O, He, and Mg ions observed by ACE/SWICS concurrent with Genesis observations, and compare these to the Genesis algorithm decisions. Not only does this serve as a test of the algorithm, the compilation of composition vs. regime will be important for comparison to the abundances determined from sample analysis at the end of the mission.

Distributed Sensor Network With Collective Computation For Situational Awareness

Initiated under Laboratory Directed R&D funding we have engaged in empirical studies, theory development, and initial hardware development for a ground‐based Distributed Sensor Network with Collective Computation (DSN‐CC). A DSN‐CC is a network that uses node‐to‐node communication and on‐board processing to achieve gains in response time, power usage, communication bandwidth, detection resolution, and robustness. DSN‐CCs are applicable to both military and civilian problems where massive amounts of data gathered over a large area must be processed to yield timely conclusions. We have built prototype hardware DSN‐CC nodes. Each node has self‐contained power and is 6”×10”×2”. Each node contains a battery pack with power feed from a solar panel that forms the lid, a central processing board, a GPS card, and radio card. Further system properties will be discussed, as will scenarios in which the system might be used to counter Nuclear/Biological/Chemical (NBC) threats of unconventional warfare. Mid‐year in FY0...

A validation payload for space and atmospheric nuclear event detection

We describe an experimental flight validation payload for detecting atmospheric and space nuclear events with a planned launch date in 2004. The five detector subsystems in the payload employ 27 sensors including Si, CdZnTe, gas proportional counter tubes, photomultiplier tubes, channel electron multipliers and photodiodes. Detection of events is based on simultaneous measurements of gamma rays, neutrons, and charged particles with wide dynamic ranges of deposited energy and count rates. The sensors and electronics are housed in one package with approximate mass and power consumption of 27 kg and 50 watts, respectively. The instrument uses sophisticated on-board digital signal processing and multi-layer triggering algorithms to detect and assess the validity of small signals in a large background radiation environment. This paper presents system configuration and preliminary test data from the first of the two units in development.

Comparative Response of Microchannel Plate and Channel Electron Multiplier Detectors to Penetrating Radiation in Space

Channel electron multiplier (CEM) and microchannel plate (MCP) detectors are routinely used in space instrumentation for measurement of space plasmas. Our goal is to understand the relative sensitivities of these detectors to penetrating radiation in space, which can generate background counts and shorten detector lifetime. We use 662 keV γ-rays as a proxy for penetrating radiation such as γ-rays, cosmic rays, and high-energy electrons and protons that are ubiquitous in the space environment. We find that MCP detectors are ~ 20 times more sensitive to 662 keV γ-rays than CEM detectors. This is attributed to the larger total area of multiplication channels in an MCP detector that is sensitive to electronic excitation and ionization resulting from the interaction of penetrating radiation with the detector material. In contrast to the CEM detector, whose quantum efficiency εγ for 662 keV γ-rays is found to be 0.00175 and largely independent of detector bias, the quantum efficiency of the MCP detector is strongly dependent on the detector bias, with a power law index of 5.5. Background counts in MCP detectors from penetrating radiation can be reduced using MCP geometries with higher pitch and smaller channel diameter.

New Magnetospheric Ion Composition Measurement Techniques

This paper provides a brief overview of three new instruments designed to measure ion composition in the magnetosphere at energies from a few eV/q to a maximum of 200 keV/q. Ion composition is not currently monitored at geosynchronous orbit and is an important ingredient to understand the dynamic near‐Earth space environment. The unique ion composition measurement techniques in the detector sections following an electrostatic analyzer are the focus of this paper. The first instrument for geosynchronous orbit, the Advanced Miniaturized Plasma Spectrometer (AMPS), exploits the properties of a solid‐state detector to measure ion composition by an E/q x E technique. The Z Plasma Spectrometer (ZPS) design, also for geosynchronous orbit, uses selective filtering by different thicknesses of carbon foil to separate H+ from O+. The third instrument, the Helium Oxygen Proton Electron spectrometer (HOPE), was selected for the upcoming Radiation Belt Storm Probes mission (RBSP) and uses a gated time‐of‐flight (TOF) t...

Genesis mission to return solar winds samples to Earth

The Genesis spacecraft, launched on 8 August 2001 from Cape Canaveral, Florida, will be the first spacecraft ever to return from interplanetary space. The fifth in NASAs line of low-cost, Discovery-class missions, its goal is to collect samples of solar wind and return them to Earth for detailed isotopic and elemental analysis. The spacecraft is to collect solar wind for over 2 years, while circling the L1 point 1.5 million km Sunward of the Earth, before heading back for a capsule-style re-entry in September 2004. After parachute deployments mid-air helicopter recovery will be used to avoid a hard landing. The mission has been in development over 10 years, and its cost, including development, mission operations, and initial sample analysis, is approximately

Foil electron multiplier

209 million.