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NASA NTRS1994

Perceptual Repetition Blindness Effects

The phenomenon of repetition blindness (RB) may reveal a new limitation on human perceptual processing. Recently, however, researchers have attributed RB to post-perceptual processes such as memory retrieval and/or reporting biases. The standard rapid serial visual presentation (RSVP) paradigm used in most RB studies is, indeed, open to such objections. Here we investigate RB using a "single-frame" paradigm introduced by Johnston and Hale (1984) in which memory demands are minimal. Subjects made only a single judgement about whether one masked target word was the same or different than a post-target probe. Confidence ratings permitted use of signal detection methods to assess sensitivity and bias effects. In the critical condition for RB a precue of the post-target word was provided prior to the target stimulus (identity precue), so that the required judgement amounted to whether the target did or did not repeat the precue word. In control treatments, the precue was either an unrelated word or a dummy.

Hochhaus, Larry↗
NASA NTRS2001

Rocket and Laboratory Studies in Astronomy

This is the final report for NASA Grant NAG5-5122 and covers the period from March 1, 1997 to February 28, 2001. This grant was a continuation of a program in rocket and laboratory studies in ultraviolet astronomy that was supported by NASA grant NAG5-619. As of March 1, 2001, this program is continuing under grant NAG5-5315. During the period of the grant, annual status reports have been submitted detailing the scientific achievements and current objectives of each report period. These will not be repeated here. Among the highlights of the program are four successful rocket launches including participation in the campaign to study comet Hale-Bopp in April 1997. We have continued our emphasis on long-slit spectroscopy of extended sources in the shorter wavelength far-ultraviolet, necessitating the development of evacuated telescope/spectrograph payloads. Finally, we also note the use of our ultraviolet calibration facilities in support of other sounding rocket investigators and for other space missions such as the Far Ultraviolet Spectroscopic Explorer. We include a list of the sounding rocket launches performed under NASA sponsorship during this period, a list of Ph.D. degrees awarded to students who worked in this program, and a summary bibliography of publications between 1997 and 2001.

Feldman, Paul D.↗
NASA NTRS2002

Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge Exchange Cross Sections

The detection of X-rays from comets such as Hyakutake, Hale-Bopp, d Arrest, and Linear as they approach the Sun has been unexpected and exciting. This phenomenon, moreover, should be quite general, occurring wherever a fast solar or stellar wind interacts with neutrals in a comet, a planetary atmosphere, or a circumstellar cloud. The process is, O(+8) + H2O --> O(+7*) + H2O(+), where the excited O(+7*) ions are the source of the X-ray emissions. Detailed modeling has been carried out of X-ray emissions in charge-transfer collisions of heavy solar-wind Highly Charged Ions (HCIs) and interstellar/interplanetary neutral clouds. In the interplanetary medium the solar wind ions, including protons, can charge exchange with interstellar H and He. This can give rise to a soft X-ray background that could be correlated with the long-term enhancements seen in the low-energy X-ray spectrum of ROSAT. Approximately 40% of the soft X-ray background detected by Exosat, ROSAT, Chandra, etc. is due to Charge Exchange (CXE): our whole heliosphere is glowing in the soft X-ray due to CXE.

Chutjian, A.↗
NASA NTRS2003

Infrared Spectroscopy of the Dust in Comets and Relationships to Interstellar Dust

Infrared spectroscopy of the dust in comets reveals a complex mix of silicate materials, including both crystalline and non-crystalline components of both olivine (forsterite) and pyroxene composition. These various components do not necessarily share a common origin. Since comets formed in cold regions of the solar nebula, pre-solar grains in the nebula could have been accreted into comets with little alteration. Some of the cometary silicates may be of circumstellar (formed in circumstellar outflows of evolved stars) or interstellar (formed in dense region of the interstellar medium) origin. Spectral similarities to both circumstellar and interstellar silicates are seen in comet spectra. the short-period Kuiper Belt comets) show weak or no spectral features. The lack of features is generally explained as a particle size effect: the small silicate grains are embedded in larger, optically thick particles. However, compositional differences cannot be ruled out. For example, no unambiguous signature of forsterite has yet been seen in the spectrum of a short-period comet. Thus, the Stardust sample from short-period comet P/Wild 2 will be extremely valuable. Not only grain by grain composition and isotopic ratios but also grain morphology, irradiation history, and evidence of organic refractory mantles are important for understanding their origin. The relative abundance and distinguishing characteristics of the various crystalline and non-crystalline silicate components needs to be established. While some comets, such as Hale-Bopp, display a rich infrared spectrum, others (particularly

Hanner, Martha S.↗
NASA NTRS2003

Mound Spring Complexes in Central Australia: An Analog for Martian Groundwater Fed Outflow Channels?

The arid inland of Australia contains a diversity of landscapes and landscape processes, often of great antiquity, extending back to the Mesozoic and Paleozoic. The potential of this landscape as a source of Mars analogs has, however, been little explored. The few examples studied so far include radiation-tolerant microbes in thermal springs and hematite-silica hydrothermal alteration near Arkaroola in the Finders Ranges, and aeolian landforms at Gurra Gurra water hole the north east of Arkaroola. Further Australian Mars analog studies were provided by the studies of Bourke and Zimbelman of the paleoflood record of the Todd and Hale Rivers in central Australia. To facilitate study of such analogues, Mars Society Australia has embarked on a project to construct a Mars Analog Research Station near Arkaroola. The international scientific community will soon have the opportunity to participate in Mars analog studies in central Australia utilizing this facility. An area of considerable Mars analog potential is the mound spring complexes that occur at the margins of the Great Artesian Basin (GAB) which underlies 22% of the Australian continent and covers 1.7 million km2. The mound springs are formed when ground water flows to a topographic low, and subsurface strata dips up causing a hydrological head at the surface. Minerals precipitated at the spring discharge zone form low mesas or "mounds", the height of which are controlled by the hydrological head. This paper describes the Dalhousie Mound Spring Complex (DMC) in the northern part of South Australia (Figure 1), and its potential as a Mars analog. Hydrogeology: The DMC consists of a cluster of more than 60 active springs formed by natural discharge from the GAB). Total measured discharge from the GAB is 1.74 GL per day, estimated unfocussed natural leakage through the aquaclude is thought be approximately equal to this figure. Some 54 ML per day are currently discharged by the DMC, 3% of the measured total. The discharged artesian waters are of low to moderate salinity (700 - 9400 ppm), near neutral pH (6.8-7.3) and warm (20-46 C). The elevated temperatures are due to passage of the groundwater through deeply buried (up to 3 km) aquifers in an region of high heat flow, rather than magmatic heating. The waters also contain high levels of dissolved iron and H2S and less than 1 ppm dissolved oxygen. The water is carried in the Late Jurassic Algebuckina Sandstone beneath the aquaclude of the Bulldog Shale. It is brought near the surface by the mid-Cenozoic Dalhousie anticline and the ground water flow focused along a series of faults that breach the anticline's crest.

Clarke, J. D. A.↗
NASA NTRS2003

Space Science Reference Guide, 2nd Edition

This Edition contains the following reports: GRACE: Gravity Recovery and Climate Experiment; Impact Craters in the Solar System; 1997 Apparition of Comet Hale-Bopp Historical Comet Observations; Baby Stars in Orion Solve Solar System Mystery; The Center of the Galaxy; The First Rock in the Solar System; Fun Times with Cosmic Rays; The Gamma-Ray Burst Next Door; The Genesis Mission: An Overview; The Genesis Solar Wind Sample Return Mission; How to Build a Supermassive Black Hole; Journey to the Center of a Neutron Star; Kepler's Laws of Planetary Motion; The Kuiper Belt and Oort Cloud ; Mapping the Baby Universe; More Hidden Black Hole Dangers; A Polarized Universe; Presolar Grains of Star Dust: Astronomy Studied with Microscopes; Ring Around the Black Hole; Searching Antarctic Ice for Meteorites; The Sun; Astrobiology: The Search for Life in the Universe; Europa and Titan: Oceans in the Outer Solar System?; Rules for Identifying Ancient Life; Inspire ; Remote Sensing; What is the Electromagnetic Spectrum? What is Infrared? How was the Infrared Discovered?; Brief History of Gyroscopes ; Genesis Discovery Mission: Science Canister Processing at JSC; Genesis Solar-Wind Sample Return Mission: The Materials ; ICESat: Ice, Cloud, and Land Elevation Satellite ICESat: Ice, Cloud, and Land; Elevation Satellite ICESat: Ice, Cloud, and Land Elevation Satellite ICESat: Ice, Cloud, and Land Elevation Satellite ICESat: Ice, Cloud, and Land Elevation Satellite Measuring Temperature Reading; The Optical Telescope ; Space Instruments General Considerations; Damage by Impact: The Case at Meteor Crater, Arizona; Mercury Unveiled; New Data, New Ideas, and Lively Debate about Mercury; Origin of the Earth and Moon; Space Weather: The Invisible Foe; Uranus, Neptune, and the Mountains of the Moon; Dirty Ice on Mars; For a Cup of Water on Mars; Life on Mars?; The Martian Interior; Meteorites from Mars, Rocks from Canada; Organic Compounds in Martian Meteorites May be Terrestrial Contaminants; Bands on Europa;Big Mountain, Big Landslide on Jupiter's Moon, Io; Cratering of the Moon; Europa's Salty Surface; The Europa Scene in the Voyager-Galileo Era; Explosive Volcanic Eruptions on the Moon; Ice on the Bone Dry Moon; Jupiter's Hot, Mushy Moon; The Moon Beyond 2002 ; Phases of the Moon; The Ph-D Project: Manned Expedition to the Moons of Mars; and Possible Life in a Europan Ocean.

Dotson, Renee↗
NASA NTRS2004

Infrared Observations of Cometary Dust and Nuclei

This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

Lisse, Carey↗
NASA NTRS1999

Irradiated interplanetary dust particles as a possible solution for the deuterium/hydrogen paradox of Earth's oceans

Determining the source of Earth's oceans is a longstanding problem in planetary science. Possible sources of water include water ice or water of hydration of silicate minerals in the original material from which the bulk Earth accreted and water brought in by late-arriving planetesimals during the heavy bombardment period (4.5-3.8 Gyr ago) [Chyba, 1989, 1991]. Comets are an attractive source of water because their origin in the outer solar system is consistent with the long timescale for heavy bombardment. However, the high deuterium/hydrogen (D/H) ratio of the three comets that have been studied, Halley, Hyakutake, and Hale-Bopp, indicates that Earth must have had a source with a low-D/H ratio as well. Here we suggest that solar wind-implanted hydrogen on interplanetary dust particles (IDPs) provided the necessary low-D/H component of Earth's water inventory.

Non-NASA Center↗
NASA NTRS1998

Chemistry in cometary comae

Significant gas-phase chemistry occurs in the comae of bright comets, as is demonstrated here for the case of Comet Hale-Bopp. The abundance ratio of the two isomers, hydrogen cyanide and hydrogen isocyanide, is shown to vary with heliocentric distance in a way that is consistent with production of HNC by ion-molecule chemistry initiated by the photoionization of water. Likewise, the first maps of emission from HCO+ show an abundance and an extended distribution that are consistent with the same chemical model.

Non-NASA Center↗
NASA NTRS2004

Modelling and Analysis of a Regenerative Fuel Cell Propulsion System for a High Altitude Long Endurance UAV

In the search to bridge current gaps in surveillance and communication technologies, a new type of, aircraft is currently undergoing design. The idea of a High Altitude Long Endurance (HALE) aircraft is already a few decades old, but has only recently become realizable. A relay and collector of information at altitudes of 65,000 feet and higher could greatly improve standards of data exchange, homeland security, and research of the air, land and sea. NASA, as a major force in propulsion research, is exploring methods of powering an autonomous aircraft for days, weeks, or even months without refueling. Such a task requires not only high energy density, but also the ability to make use of renewable energy sources to regenerate power. Hydrogen is one of the most energy dense fuels available. Fuel cells make use of hydrogen by harnessing the energy released as it combines with oxygen to produce electricity and water. Fuel cells are envisioned to occupy future propulsion systems in cooperation with solar cells where the photovoltaic arrays harness sunlight into power which can electrolize the water byproduct into reusable hydrogen and oxygen. Modeling this type of system requires adequate assumptions of support hardware and daily transients in operation. The performance of a regenerative fuel cell propulsion system lies in the flight characteristics (altitude, density, temperature, latitude, etc.). Each subsystem is defined by many parameters which can be varied across wide ranges. Statistical and probabilistic analyses bring forward a wealth of information that can be utilized in the design process. This is necessary since the required technologies are relatively young and barely, if yet, capable. Once the modeling is complete, a design space exploration of this highly constrained scenario can be utilized to find the optimal design. The model will become an interactive environment with which experiments and tests can be run. When linked

Simpson, Mike B.↗
NASA NTRS2005

Hydrogen-powered flight

As the Nation moves towards a hydrogen economy the shape of aviation will change dramatically. To accommodate a switch to hydrogen the aircraft designs, propulsion, and power systems will look much different than the systems of today. Hydrogen will enable a number of new aircraft capabilities from high altitude long endurance remotely operated aircraft (HALE ROA) that will fly weeks to months without refueling to clean, zero emissions transport aircraft. Design and development of new hydrogen powered aircraft have a number of challenges which must be addressed before an operational system can become a reality. While the switch to hydrogen will be most outwardly noticeable in the aircraft designs of the future, other significant changes will be occurring in the environment. A switch to hydrogen for aircraft will completely eliminate harmful greenhouse gases such as carbon monoxide (CO), carbon dioxide (CO2), sulfur oxides (SOx), unburnt hydrocarbons and smoke. While these aircraft emissions are a small percentage of the amount produced on a daily basis, their placement in the upper atmosphere make them particularly harmful. Another troublesome gaseous emission from aircraft is nitrogen oxides (NOx) which contribute to ozone depletion in the upper atmosphere. Nitrogen oxide emissions are produced during the combustion process and are primarily a function of combustion temperature and residence time. The introduction of hydrogen to a gas turbine propulsion system will not eliminate NOx emissions; however the wide flammability range will make low NOx producing, lean burning systems feasible. A revolutionary approach to completely eliminating NOx would be to fly all electric aircraft powered by hydrogen air fuel cells. The fuel cells systems would only produce water, which could be captured on board or released in the lower altitudes. Currently fuel cell systems do not have sufficient energy densities for use in large aircraft, but the long term potential of eliminating greenhouse gas emissions makes it an intriguing and important field of research.

Smith, Timothy D.↗
NASA NTRS2005

STS-114: Discovery Launch Readiness Press Conference

This press conference, attended by representatives from the national, Florida, and aerospace media, addresses launch, weather, and safety issues related to Space Shuttle Discovery prior to its launch on the STS-114 Return to Flight mission. The Master of Ceremonies is George Diller from NASA Public Affairs, and the panelists are: Space Shuttle Program Manager Bill Parsons, ISS Program Manager (JSC) Bill Gerstenmaier, Space Shuttle Deputy Program Manager Wayne Hale, Director of Shuttle Processing Mike Wetmore, ISS Program Manager (JAXA) Dr. Kuniaki Shiraki, and Launch Weather Officer (USAF) Mindy Chavez. Questions included the following topics: predicted weather conditions at launch, contingency rescue plans, countdown procedures, and risk management, as well as implications of the Return to Flight for the International Space Station (ISS).

Source record↗
NASA NTRS2005

STS-114: Discovery Post MMT Press Conference

This press conference focuses on the outcome of the Mission Management Team (MMT) meeting. The launch and status of the Space Shuttle Discovery is discussed. George Diller from NASA Public Affairs introduces the panel which consists of: Wayne Hale, Space Shuttle Program Deputy Manager and Mike Wetmore, Director of Space Shuttle Processing at Nasa Kennedy Space Center. The news media asks questions about the history of the low level sensors in the hydrogen tank, the cryogenic atmosphere around the sensors, troubleshooting, astronaut activities, possible rollback procedures.

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NASA NTRS2005

STS-114: Discovery Day 6 Post MMT Meeting

Wayne Hale, Space Shuttle Deputy Program Manager and Steve Poulos, Orbiter Program Manager, discuss the damage assessment from the tiles that came off the Space Shuttle Discovery during launch. Poulos presents charts and discusses in detail the following topics: 1) Composite Tile Damage/Gap Filler Sites Evaluation; 2) Protruding Ceramic Shim Aft of the Nose Landing Gear Door (NLGD); 3) Protruding Chine Gap Filler; 4) RH NLGD Tile Damage; 5) RH NLGD Damage Analysis; 6) Left Wing Tile Damage; 7) Comparison of Ground Test Results vs. FD5 Focused Inspection; 8) Current Status: Focused Inspection 721L07-01 ITVC FD5 Image of Panel 7L Apex 9) Current Status: Focused Inspection Lower Panel 7L721L07-02; 10) Current Status Focused Inspection 721L10-02 Lower Panel 10L Close-up view; and 11) Window 1 Blanket. The presentation ends with a question and answer period from the news media.

Source record↗
NASA NTRS2005

STS-114: Discovery Post MMT Briefing

Wayne Hale, Space Shuttle Deputy Program Manager, discusses the topics covered at the Mission Management Team (MMT) meeting. The topics include: 1) Wing leading edge reinforced carbon-carbon clearance; 2) Protruding blanket on the side of the Space Shuttle Discovery Orbiter; 3) Control Moment Gyroscope (CMG) replacement; 4) Transfer items; and 5) EVA procedures. Questions from the news media about the possibility of a CMG failure, Space Shuttle re-entry, gap fillers, and dangers during the EVA to repair the Space Shuttle Discovery are answered.

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NASA NTRS2005

Various Analyses of Structures and Systems Pertaining to Optical Communications

The Optical Communications Group intends to experiment with a 2 by 2 meter Fresnel lens to determine its likelihood as an alternative to focusing mirrors for optical communications. The lens was delivered in four sections. A support structure was required for the lens in order to hold the four sections in a single flat plane with an adjustable degree angle. In order to use the 200-in. Hale telescope for optical communications purposes, an optical filter membrane must used to pass the communications wavelength while blocking sunlight wavelengths. This filter must withstand wind gusts of up to 50 miles per hour. Stress analysis predicts that the membrane will survive with a safety factor greater than two. The methods used were verified by pressure testing the material. Mechanical and thermodynamic analyses were performed on a simple Golay cell in order to optimize its dimensions for best performance. Flexures are examined as an inexpensive alternative to traditional methods for kinematically constraining a 1.5-meter spherical mirror.

Petersen, Collin W.↗
NASA NTRS2006

STS-121/Discovery Preflight Briefing Program Overview

Wayne Hale (Space Shuttle Program Manager) opens with a short video of the external tank operation and the Shuttle roll out to the launch pad. Kirk Shireman (International Space Station Program Deputy Manager) shows a video of International Space Station activities which included replacement of the remote power switch, unloading of cargo, Earth observation (over 23,000 photos taken), exercises, and replacement of the Camera during a spacewalk.

Source record↗
NASA NTRS2005

Space Shuttle Status News Conference

Richard Gilbech, External Tank "Tiger Team" Lead, begins this space shuttle news conference with detailing the two major objectives of the team. The objectives include: 1) Finding the root cause of the foam loss on STS-114; and 2) Near and long term improvements for the external tank. Wayne Hale, Space Shuttle Program Manager, presents a chart to explain the external tank foam loss during STS-114. He gives a possible launch date for STS-121 after there has been a repair to the foam on the External Tank. He further discusses the changes that need to be made to the surrounding areas of the plant in New Orleans, due to Hurricane Katrina. Bill Gerstemaier, NASA Associate Administrator for Space Operations, elaborates on the testing of the external tank foam loss. The discussion ends with questions from the news media about a fix for the foam, replacement of the tiles, foam loss avoidance, the root cause of foam loss and a possible date for a new external tank to be shipped to NASA Kennedy Space Center.

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