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NASA NTRS2001

Large-Scale Mini-Magnetosphere Plasma Propulsion (M2P2) Experiments

Mini-Magnetosphere Plasma Propulsion (M2P2) is an innovative plasma propulsion system that has the potential to propel spacecraft at unprecedented speeds of 50 to 80 km per second with a low-power requirement of approx. 1 kW per 100 kg of payload and approx. 1 kg of neutral gas [fuel] consumption per day of acceleration. Acceleration periods from several days to a few months are envisioned. High specific impulse and efficiency are achieved through coupling of the spacecraft to the 400 km per second solar wind through an artificial magnetosphere. The mini-magnetosphere or inflated magnetic bubble is produced by the injection of cold dense plasma into a spacecraft-generated magnetic field envelope. Magnetic bubble inflation is driven by electromagnetic processes thereby avoiding the material and deployment problems faced by mechanical solar sail designs, Here, we present the theoretical design of M2P2 as well as initial results from experimental testing of an M2P2 prototype demonstrating: 1) inflation of the dipole magnetic field geometry through the internal injection of cold plasma; and 2) deflection of and artificial solar wind by the prototype M2P2 system. In addition, we present plans for direct laboratory measurement of thrust imparted to a prototype M2P2 by an artificial solar wind during the summer of 2001.

Winglee, R. M.↗
NASA NTRS2001

Remote Sensing of Wind Fields and Aerosol Distribution with Airborne Scanning Doppler Lidar

The coherent Doppler laser radar (lidar), when operated from an airborne platform, is a unique tool for the study of atmospheric and surface processes and features. This is especially true for scientific objectives requiring measurements in optically-clear air, where other remote sensing technologies such as Doppler radar are typically at a disadvantage. The atmospheric lidar remote sensing groups of several US institutions, led by Marshall Space Flight Center, have developed an airborne coherent Doppler lidar capable of mapping the wind field and aerosol structure in three dimensions. The instrument consists of an eye-safe approx. 1 Joule/pulse lidar transceiver, telescope, scanner, inertial measurement unit, and flight computer system to orchestrate all subsystem functions and tasks. The scanner is capable of directing the expanded lidar beam in a variety of ways, in order to extract vertically-resolved wind fields. Horizontal resolution is approx. 1 km; vertical resolution is even finer. Winds are obtained by measuring backscattered, Doppler-shifted laser radiation from naturally-occurring aerosol particles (of order 1 micron diameter). Measurement coverage depends on aerosol spatial distribution and composition. Velocity accuracy has been verified to be approx. 1 meter per second. A variety of applications have been demonstrated during the three flight campaigns conducted during 1995-1998. Examples will be shown during the presentation. In 1995, boundary layer winds over the ocean were mapped with unprecedented resolution. In 1996, unique measurements were made of. flow over the complex terrain of the Aleutian Islands; interaction of the marine boundary layer jet with the California coastal mountain range; a weak dry line in Texas - New Mexico; the angular dependence of sea surface scattering; and in-flight radiometric calibration using the surface of White Sands National Monument. In 1998, the first measurements of eyewall and boundary layer winds within a hurricane were made with the airborne Doppler lidar. Potential applications and plans for improvement will also be described.

Rothermel, Jeffry↗
NASA NTRS2001

Characteristics of the Time Variable Component of the Coronal Heating Process

The goal of the proposed study was to explore the non-steady nature of the coronal heating processes and its manifestations in the inner corona and interplanetary space by coordinating coronal SOHO observations in white light, ultraviolet, and extreme ultraviolet, with complementary radio occultation measurements during an unprecedented and rare coincidence of a total solar eclipse with the superior conjunction of a planetary spacecraft, Galileo, in February 1998. In addition, radio occultation measurements by the Mars Global Surveyor spacecraft in May 1998 spanned the inner heliosphere observed by coronal SOHO instruments and probing it to within 0.5 R(sub S), above the solar surface. Inferences of physical properties derived from these simultaneous observations were subsequently used in solar wind model computations to yield the range of plasma parameters characteristic of the fast and slow solar wind.

Habbal, Shadia R.↗
NASA NTRS2001

A Geosynchronous Lidar System for Atmospheric Winds and Moisture Measurements

An observing system comprised of two lidars in geosychronous orbit would enable the synoptic and meso-scale measurement of atmospheric winds and moisture both of which are key first-order variables of the Earth's weather equation. Simultaneous measurement of these parameters at fast revisit rates promises large advancements in our weather prediction skills. Such capabilities would be unprecedented and a) yield greatly improved and finer resolution initial conditions for models, b) make existing costly and cumbersome measurement approaches obsolete, and c) obviate the use of numerical techniques needed to correct data obtained using present observing systems. Additionally, simultaneous synoptic wind and moisture observations would lead to improvements in model parameterizations, and in our knowledge of small-scale weather processes. Technology and science data product assessments are ongoing. Results will be presented during the conference.

Emmitt, G. D.↗
NASA NTRS2001

A Study of the Structure of the Source Region of the Solar Wind in Support of a Solar Probe Mission

Despite the richness of the information about the physical properties and the structure of the solar wind provided by the Ulysses and SOHO (Solar and Heliospheric Observatory) observations, fundamental questions regarding the nature of the coronal heating mechanisms, their source, and the manifestations of the fast and slow solar wind, still remain unanswered. The last unexplored frontier to establish the connection between the structure and dynamics of the solar atmosphere, its extension into interplanetary space, and the mechanisms responsible for the evolution of the solar wind, is the corona between 1 and 30 R(sub s). A Solar Probe mission offers an unprecedented opportunity to explore this frontier. Its uniqueness stems from its trajectory in a plane perpendicular to the ecliptic which reaches within 9 R(sub s) of the solar surface over the poles and 3 - 9 R(sub s) at the equator. With a complement of simultaneous in situ and remote sensing observations, this mission is destined to detect remnants and signatures of the processes which heat the corona and accelerate the solar wind. In support of this mission, we fulfilled the following two long-term projects: (1) Study of the evolution of waves and turbulence in the solar wind (2) Exploration of signatures of physical processes and structures in the corona. A summary of the tasks achieved in support of these projects are given below. In addition, funds were provided to support the Solar Wind 9 International Conference which was held in October 1998. A brief report on the conference is also described in what follows.

Habbal, Shadia R.↗
NASA NTRS2001

Are Soft Gamma-ray Repeaters (SGRs) 'Magnetars'?

Soft Gamma-ray repeaters (SGRs) are among the most powerful Galactic sources of high energy radiation. These objects are even powerful enough to influence processes occurring in the near Earth environment. In the last few years X-ray observations with the Rossi X-ray Timing Explorer (RXTE) have provided us with a new understanding of SGRs. RXTE was instrumental in the discovery that SGRs are rapidly slowing X-ray pulsars and is still providing continued monitoring of their pulse periods. SGR bursts have now been observed with unprecedented sensitivity. I will review the current status of our knowledge of SGRs based on these recent X-ray observations and discuss their implications for models of SGRs, including the now substantial evidence that these objects are highly magnetized neutron stars or 'magnetars'. I will also describe recent spectral studies of SGR bursts which have revealed several new phenomena, including a burst with strong spectral evolution and evidence for a 6.4 keV emission line.

Strohmayer, Tod E.↗
NASA NTRS2001

The Aqua-Aura Train

This talk will focus on the afternoon constellation of EOS platforms and the scientific benefits that arise from this formation. The afternoon EOS constellation or the "A-train" will provide unprecedented information on clouds and aerosols. At 1:30 PM crossing time EOS-Aqua begins the train with the MODIS, CERES and AIRS instruments making aerosol, cloud, radiation budget , temperature and water vapor measurements. AMSR-E will also make total column water measurements. Following Aqua by one minute, Cloudsat will make active radar precipitation measurements as and PICASSOCENA will make lidar measurements of clouds and aerosols. Fourteen minutes later, EOS-Aura will pass through the same space making upper troposphere water vapor and ice profiles as well as some key trace gases associated with convective processes (MLS and HIRDLS). Additional measurements of aerosols will be made by Aura's OMI instrument.

Schoeberl, Mark↗
NASA NTRS2000

Interannual Variability in the Meridional Transport of Water Vapor

The zonal-mean meridional transport of water vapor across the globe is evaluated using the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis for 1948-97. The shape of the meridional profile of the climatological mean transport closely resembles that of previous mean climate descriptions, but values tend to be notably larger than in climatologies derived from radiosonde-only-based analyses. The unprecedented length of the NCEP-NCAR dataset invites a focus on interannual variations in the zonal-mean moisture transport, and these results for northern winter are highlighted here. Although interannual variability in the transport is typically small at most latitudes, a significant ENSO signal is present, marked by a strengthening of water vapor transports over much of the winter hemisphere during warm events. Because of an increase in tropical sea surface temperatures and in the frequency of warm events relative to cold events in the latter half of the 50-yr record, this interannual signal projects onto an overall trend toward enhanced meridional moisture transports in the global hydrological cycle.

Cohen, Judah L.↗
NASA NTRS2001

Optical Design of the MOSES Sounding Rocket Experiment

The Multi-Order Solar EUV Spectrograph (MOSES) is a sounding rocket payload now being developed by Montana State University in collaboration with the Goddard Space Flight Center, Lockheed Martin Advanced Technology Center, and Mullard Space Science Laboratory. The instrument utilizes a unique optical design to provide solar EUV measurements with true 2-pixel resolutions of 1.0 arcsec and 60 mA over a full two-dimensional field of view of 1056 x 528 arcsec, all at a time cadence of 10 s. This unprecedented capability is achieved by means of an objective spherical grating 100 mm in diameter, ruled at 833 gr/mm. The concave grating focuses spectrally dispersed solar radiation onto three separate detectors, simultaneously recording the zero-order as well as the plus and minus first-spectral-order images. Data analysis procedures, similar to those used in X-ray tomography reconstructions, can then disentangle the mixed spatial and spectral information recorded by the multiple detectors. A flat folding mirror permits an imaging focal length of 4.74 m to be packaged within the payload's physical length of 2.82 m. Both the objective grating and folding flat have specialized, closely matched, multilayer coatings that strongly enhance their EUV reflectance while also suppressing off-band radiation that would otherwise complicate data inversion. Although the spectral bandpass is rather narrow, several candidate wavelength intervals are available to carry out truly unique scientific studies of the outer solar atmosphere. Initial flights of MOSES, scheduled to begin in 2004, will observe a 10 Angstrom band that covers very strong emission lines characteristic of both the sun's corona (Si XI 303 Angstroms) and transition-region (He II 304 Angstroms). The MOSES program is supported by a grant from NASA's Office of Space Science.

Thomas, Roger J.↗
NASA NTRS2001

HERO: Program Status and Fist Images from a Balloon-Borne Focusing Hard-X-ray Telescope

HERO is a balloon payload featuring shallow-graze angle replicated optics for hard-x-ray imaging. When completed, the instrument will offer unprecedented sensitivity in the hard-x-ray region, giving thousands of sources to choose from for detailed study on long flights. A recent proof-of-concept flight captured the first hard-x-ray focused images of the Crab Nebula, Cygnus X-1 and GRS 1915+105. Full details of the HERO program are presented, including the design and performance of the optics, the detectors and the gondola. Results from the recent proving flight are discussed together with expected future performance when the full science payload is completed.

Ramsey, B. D.↗
NASA NTRS2001

The GLAST Burst Monitor

The GLAST Burst Monitor The Gamma Ray Large Area Space Telescope, scheduled for launch in 2006, comprises a Large Area Telescope (LAT) and a GLAST Burst Monitor (GBM). The LAT is a pair telescope with unprecedented sensitivity in the 20 Mev to 300 GeV energy range. The GLAST Burst Monitor (GBM) consists of an array of NaI and BGO scintillation detectors operating in the 10 kev to 30 MeV range and covering a wide field of view. The GBM will enhance LAT observations of GRBs by extending the spectral coverage into the range of current GRB databases, and will provide a trigger for re-orienting the spacecraft to observe delayed emission from bursts outside the LAT field of view.

Meegan, C. A.↗
NASA NTRS2001

ECCO: Th/U/Pu/Cm Dating of Galactic Cosmic Ray Nuclei

The ECCO (Extremely-heavy Cosmic-ray Composition Observer) instrument is one of two instruments which comprise the HNX (Heavy Nuclei Explorer) mission. The principal goal of ECCO is to measure the age of galactic cosmic ray nuclei using the actinides (Th, U, Pu, Cm) as clocks. As a bonus, ECCO will search with unprecedented sensitivity for long-lived elements in the superheavy island of stability. ECCO is an enormous array (23 sq. m) of BP-1 glass track-etch detectors, and is based on the successful flight heritage of the Trek detector which was deployed externally on Mir. We present a description of the instrument, estimates of expected performance, and recent calibrations which demonstrate that the actinides can be resolved from each other with good charge resolution.

Westphal, A. J.↗
NASA NTRS2002

A Pilot Computer-Aided Design and Manufacturing Curriculum that Promotes Engineering

Elizabeth City State University (ECSU) is located in a community that is mostly rural in nature. The area is economically deprived when compared to the rest of the state. Many businesses lack the computerized equipment and skills needed to propel upward in today's technologically advanced society. This project will close the ever-widening gap between advantaged and disadvantaged workers as well as increase their participation with industry, NASA and/or other governmental agencies. Everyone recognizes computer technology as the catalyst for advances in design, prototyping, and manufacturing or the art of machining. Unprecedented quality control and cost-efficiency improvements are recognized through the use of computer technology. This technology has changed the manufacturing industry with advanced high-tech capabilities needed by NASA. With the ever-widening digital divide, we must continue to provide computer technology to those who are socio-economically disadvantaged.

Source record↗
NASA NTRS2002

NASA Technology Investments in Electric Propulsion: New Directions in the New Millennium

The last decade was a period of unprecedented acceptance of NASA developed electric propulsion by the user community. The benefits of high performance electric propulsion systems are now widely recognized, and new technologies have been accepted across the commonly. NASA clearly recognizes the need for new, high performance, electric propulsion technologies for future solar system missions and is sponsoring aggressive efforts in this area. These efforts are mainly conducted under the Office of Aerospace Technology. Plans over the next six years include the development of next generation ion thrusters for end of decade missions. Additional efforts are planned for the development of very high power thrusters, including magnetoplasmadynamic, pulsed inductive, and VASIMR, and clusters of Hall thrusters. In addition to the in-house technology efforts, NASA continues to work closely with both supplier and user communities to maximize the acceptance of new technology in a timely and cost-effective manner. This paper provides an overview of NASA's activities in the area of electric propulsion with an emphasis on future program directions.

Sankovic, John M.↗
NASA NTRS2001

InP MMIC Chip Set for Power Sources Covering 80-170 GHz

We will present a Monolithic Millimeter-wave Integrated Circuit (MMIC) chip set which provides high output-power sources for driving diode frequency multipliers into the terahertz range. The chip set was fabricated at HRL Laboratories using a 0.1-micrometer gate-length InAlAs/InGaAs/InP high electron mobility transistor (HEMT) process, and features transistors with an f(sub max) above 600 GHz. The HRL InP HEMT process has already demonstrated amplifiers in the 60-200 GHz range. In this paper, these high frequency HEMTs form the basis for power sources up to 170 GHz. A number of state-of-the-art InP HEMT MMICs will be presented. These include voltage-controlled and fixed-tuned oscillators, power amplifiers, and an active doubler. We will first discuss an 80 GHz voltage-controlled oscillator with 5 GHz of tunability and at least 17 mW of output power, as well as a 120 GHz oscillator providing 7 mW of output power. In addition, we will present results of a power amplifier which covers the full WRIO waveguide band (75-110 GHz), and provides 40-50 mW of output power. Furthermore, we will present an active doubler at 164 GHz providing 8% bandwidth, 3 mW of output power, and an unprecedented 2 dB of conversion loss for an InP HEMT MMIC at this frequency. Finally, we will demonstrate a power amplifier to cover 140-170 GHz with 15-25 mW of output power and 8 dB gain. These components can form a power source in the 155-165 GHz range by cascading the 80 GHz oscillator, W-band power amplifier, 164 GHz active doubler and final 140-170 GHz power amplifier for a stable, compact local oscillator subsystem, which could be used for atmospheric science or astrophysics radiometers.

Ngo, Catherine↗
NASA NTRS1995

Advances in Detector Technology for Infrared Astronomy

Progress in semiconductor materials and processing technology has allowed the development of infrared detector arrays with unprecedented sensitivity, for imaging and spectroscopic applications in astronomy. The earlier discrete-detector approach has been replaced by large-element (up to 1024 x 1024 pixel), multiplexed devices. Progress has been made against a number of key limiting factors, such as quantum efficiency, noise, spectral response, linearity, and dark current. Future developments will focus on the need for even larger arrays, which operate at higher temperatures.

McCreight, Craig↗
NASA NTRS1996

Automated Decomposition of Model-based Learning Problems

A new generation of sensor rich, massively distributed autonomous systems is being developed that has the potential for unprecedented performance, such as smart buildings, reconfigurable factories, adaptive traffic systems and remote earth ecosystem monitoring. To achieve high performance these massive systems will need to accurately model themselves and their environment from sensor information. Accomplishing this on a grand scale requires automating the art of large-scale modeling. This paper presents a formalization of [\em decompositional model-based learning (DML)], a method developed by observing a modeler's expertise at decomposing large scale model estimation tasks. The method exploits a striking analogy between learning and consistency-based diagnosis. Moriarty, an implementation of DML, has been applied to thermal modeling of a smart building, demonstrating a significant improvement in learning rate.

Williams, Brian C.↗
NASA NTRS1999

Development of Optical Diagnostic Techniques for Microgravity Materials Processing

Materials processing including crystal growth, either under a gravity environment on ground or a microgravity environment in space, involves complicated phenomena of fluid motions in gas or liquid phases as well as interaction of various species. To obtain important physical insight, it is very necessary to provide gross-field optical diagnostics for monitoring various physical properties. Materials processing inhibits easy access by ordinary instruments and thus characterizing gross-field physical properties is very challenging. Typical properties of importance can be fluid velocity, temperature, and species concentration for fluids, and surface topology and defects for solids. Observing surface grow rate during crystal growth is also important. Material microstructures, i.e., integrity of crystal structures, is strongly influenced by the existence of thermally-induced flow as well as local nucleation of particles during solidification, which may act in many detrimental ways. In both ground-based and microgravity experiments, the nature of product property changes resulting from three-dimensional fluid or particle motions need be characterized. Gross-field diagnostics is thus required to identify their effects on product defects and process deficiencies. The quantitative visualization techniques can also be used for validation of numerical modeling. For optical nonintrusive gross-field diagnostic techniques, two approaches were developed as summer projects. One optical approach allows us to provide information of species concentration and temperature for monitoring in real time. The other approach, that is, the concept which is formulated for detection of surface topography measurement can provide unprecedented spatial resolution during crystal growth.

Cha, Soyoung Stephen↗