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NASA NTRS2007

Integrated Cloud-Aerosol-Radiation Product using CERES, MODIS, CALIPSO and CloudSat Data

This paper documents the development of the first integrated data set of global vertical profiles of clouds, aerosols, and radiation using the combined NASA A-Train data from the Aqua Clouds and Earth's Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and CloudSat. As part of this effort, cloud data from the CALIPSO lidar and the CloudSat radar are merged with the integrated column cloud properties from the CERES-MODIS analyses. The active and passive datasets are compared to determine commonalities and differences in order to facilitate the development of a 3- dimensional cloud and aerosol dataset that will then be integrated into the CERES broadband radiance footprint. Preliminary results from the comparisons for April 2007 reveal that the CERES-MODIS global cloud amounts are, on average, 0.14 less and 0.15 greater than those from CALIPSO and CloudSat, respectively. These new data will provide unprecedented ability to test and improve global cloud and aerosol models, to investigate aerosol direct and indirect radiative forcing, and to validate the accuracy of global aerosol, cloud, and radiation data sets especially in polar regions and for multi-layered cloud conditions.

Sun-Mack, Sunny↗
NASA NTRS2008

Space Debris Symposium (A6.) Measurements and Space Surveillance (1.): Measurements of the Small Particle Debris Cloud from the 11 January, 2007 Chinese Anti-satellite Test

On January 11, 2007, the Chinese military conducted a test of an anti-satellite (ASAT) system, destroying their own Fengyun-1C spacecraft with an interceptor missile. The resulting hypervelocity collision created an unprecedented number of tracked debris - more than 2500 objects. These objects represent only those large enough for the US Space Surveillance Network (SSN) to track - typically objects larger than about 5-10 cm in diameter. There are expected to be even more debris objects at sizes too small to be seen and tracked by the SSN. Because of the altitude of the target satellite (865 x 845 km orbit), many of the debris are expected to have long orbital lifetimes and contribute to the orbital debris environment for decades to come. In the days and weeks following the ASAT test, NASA was able to use Lincoln Laboratory s Haystack radar on several occasions to observe portions of the ASAT debris cloud. Haystack has the capability of detecting objects down to less than one centimeter in diameter, and a large number of centimeter-sized particles corresponding to the ASAT cloud were clearly seen in the data. While Haystack cannot track these objects, the statistical sampling procedures NASA uses can give an accurate statistical picture of the characteristics of the debris from a breakup event. For years computer models based on data from ground hypervelocity collision tests (e.g., the SOCIT test) and orbital collision experiments (e.g., the P-78 and Delta-180 on-orbit collisions) have been used to predict the extent and characteristics of such hypervelocity collision debris clouds, but until now there have not been good ways to verify these models in the centimeter size regime. It is believed that unplanned collisions of objects in space similar to ASAT tests will drive the long-term future evolution of the debris environment in near-Earth space. Therefore, the Chinese ASAT test provides an excellent opportunity to test the models used to predict the future debris environment. For this study, Haystack detection events are compared to model predictions to test the model assumptions, including debris size distribution, velocity distribution, and assumptions about momentum transfer between the target and interceptor. In this paper we will present the results of these and other measurements on the size and extent of collisional breakup debris clouds.

Matney, Mark J.↗
NASA NTRS2004

White Light Modeling, Algorithm Development, and Validation on the Micro-arcsecond Metrology Testbed

The Space Interferometry Mission (SIM) scheduled for launch in early 2010, is an optical interferometer that will perform narrow angle and global wide angle astrometry with unprecedented accuracy, providing differential position accuracies of 1uas, and 4uas global accuracies in position, proper motion and parallax. The astrometric observations of the SIM instrument are performed via delay measurements provided by three Michelson-type, white light interferometers. Two 'guide' interferometers acquire fringes on bright guide stars in order to make highly precise measurements of variations in spacecraft attitude, while the third interferometer performs the science measurement. SIM derives its performance from a combination of precise fringe measurements of the interfered starlight (a few ten-thousandths of a wave) and very precise (tens of picometers) relative distance measurements made between a set of fiducials. The focus of the present paper is on the development and analysis of algorithms for accurate white light estimation, and on validating some of these algorithms on the MicroArcsecond Testbed.

metrology↗
NASA NTRS2007

Reconfigurable Computing Concepts for Space Missions: Universal Modular Spares

Computing hardware for control, data collection, and other purposes will prove many times over crucial resources in NASA's upcoming space missions. Ability to provide these resources within mission payload requirements, with the hardiness to operate for extended periods under potentially harsh conditions in off-World environments, is daunting enough without considering the possibility of doing so with conventional electronics. This paper examines some ideas and options, and proposes some initial approaches, for logical design of reconfigurable computing resources offering true modularity, universal compatibility, and unprecedented flexibility to service all forms and needs of mission infrastructure.

Patrick, M. Clinton↗
NASA NTRS2008

NASA Langley's Formal Methods Research in Support of the Next Generation Air Transportation System

This talk will provide a brief introduction to the formal methods developed at NASA Langley and the National Institute for Aerospace (NIA) for air traffic management applications. NASA Langley's formal methods research supports the Interagency Joint Planning and Development Office (JPDO) effort to define and develop the 2025 Next Generation Air Transportation System (NGATS). The JPDO was created by the passage of the Vision 100 Century of Aviation Reauthorization Act in Dec 2003. The NGATS vision calls for a major transformation of the nation s air transportation system that will enable growth to 3 times the traffic of the current system. The transformation will require an unprecedented level of safety-critical automation used in complex procedural operations based on 4-dimensional (4D) trajectories that enable dynamic reconfiguration of airspace scalable to geographic and temporal demand. The goal of our formal methods research is to provide verification methods that can be used to insure the safety of the NGATS system. Our work has focused on the safety assessment of concepts of operation and fundamental algorithms for conflict detection and resolution (CD&R) and self- spacing in the terminal area. Formal analysis of a concept of operations is a novel area of application of formal methods. Here one must establish that a system concept involving aircraft, pilots, and ground resources is safe. The formal analysis of algorithms is a more traditional endeavor. However, the formal analysis of ATM algorithms involves reasoning about the interaction of algorithmic logic and aircraft trajectories defined over an airspace. These trajectories are described using 2D and 3D vectors and are often constrained by trigonometric relations. Thus, in many cases it has been necessary to unload the full power of an advanced theorem prover. The verification challenge is to establish that the safety-critical algorithms produce valid solutions that are guaranteed to maintain separation under all possible scenarios. Current research has assumed perfect knowledge of the location of other aircraft in the vicinity so absolute guarantees are possible, but increasingly we are relaxing the assumptions to allow incomplete, inaccurate, and/or faulty information from communication sources.

Butler, Ricky W.↗
NASA NTRS2008

The New Horizons Mission to Pluto and Flyby of Jupiter

New Horizons (NH) is NASA's mission to provide the first in situ reconnaissance of Pluto and its moons Charon, Nix, and Hydra. The NH spacecraft will reach Pluto in July 2015 and will then, if approved for an extended mission phase, continue on to a flyby encounter with one or more Kuiper belt objects (KBOs). NH was launched on 19 January 2006 and received a gravity assist during a flyby encounter with Jupiter (with closest approach at -32 RJ on 28 February 2007) that reduced its flight time to Pluto by 3 years. During the Jupiter flyby, NH collected a trove of multi-wavelength imaging and fields-and-particles measurements. Among the many science results at Jupiter were a detection of planet-wide mesoscale waves, eruptions of atmospheric ammonia clouds, unprecedented views of Io's volcanic plumes and Jupiter's tenuous ring system, a first close-up of the Little Red Spot (LRS), first sightings of polar lightning, and a trip down the tail of the magnetosphere. In 2015, NH will conduct a seven-month investigation of the Pluto system culminating in a closest approach some 12,500 km from Pluto's surface. Planning is presently underway for the Pluto encounter with special emphasis on longidentified science goals of studying the terrain, geology, and composition of the surfaces of Pluto and Charon, examining the composition and structure of Pluto's atmosphere, searching for an atmosphere on Charon, and characterizing Pluto's ionosphere and solar wind interaction. Detailed inspections will also be performed of the newly discovered satellites Nix and Hydra. Additionally, NH will characterize energetic particles in Pluto's environment, refine the bulk properties of Pluto and Charon, and search for additional satellites and rings.

Stern, Alan↗
NASA NTRS2006

Chandra Observations of Isolated Neutron Stars

We present a review of the first six years of Chandra X-ray Observatory observations of isolated neutron stars. The outstanding spatial and spectral resolution of this great observatory have allowed for observations of unprecedented clarity and accuracy. Many of these observations have provided new insights into neutron star physics. We present a (biased) overview of six years of these observations, highlighting new discoveries made possible by the Observatory's unique capabilities.

Weisskopf, Martin↗
NASA NTRS2006

Response of Ambulatory Human Subjects to Artificial Gravity (Short Radius Centrifugation)

Prolonged exposure to microgravity results in significant adaptive changes, including cardiovascular deconditioning, muscle atrophy, bone loss, and sensorimotor reorganization, that place individuals at risk for performing physical activities after return to a gravitational environment. Planned missions to Mars include unprecedented hypogravity exposures that would likely result in unacceptable risks to crews. Artificial gravity (AG) paradigms may offer multisystem protection from the untoward effects of adaptation to the microgravity of space or the hypogravity of planetary surfaces. While the most effective AG designs would employ a rotating spacecraft, perceived issues may preclude their use. The questions of whether and how intermittent AG produced by a short radius centrifuge (SRC) could be employed have therefore sprung to the forefront of operational research. In preparing for a series of intermittent AG trials in subjects deconditioned by bed rest, we have examined the responses of several healthy, ambulatory subjects to SRC exposures.

Paloski, William H.↗
NASA NTRS2006

Leadership and Cultural Challenges in Operating the International Space Station

Operating the International Space Station (ISS) involves an indefinite, continuous series of long-duration international missions, and this requires an unprecedented degree of cooperation across multiple sites, organizations, and nations. ISS flight controllers have had to find ways to maintain effective team performance in this challenging new context. The goal of this study was to systematically identify and evaluate the major leadership and cultural challenges faces by ISS flight controllers, and to highlight the approaches that they have found most effective to surmount these challenges. We conducted a qualitative survey using a semi-structured interview. Subjects included 14 senior NASA flight controllers who were chosen on the basis of having had substantial experience working with international partners. Data were content analyzed using an iterative process with multiple coders and consensus meetings to resolve discrepancies. To further explore the meaning of the interview findings, we also conducted some new analyses of data from a previous questionnaire study of Russian and American ISS mission control personnel. The interview data showed that respondents had substantial consensus on several leadership and cultural challenges and on key strategies for dealing with them, and they offered a wide range of specific tactics for implementing these strategies. Surprisingly few respondents offered strategies for addressing the challenge of working with team members whose native language is not American English. The questionnaire data showed that Americans think it is more important than Russians that mission control personnel speak the same dialect of one shared common language. Although specific to the ISS program, our results are consistent with recent management, cultural, and aerospace research. We aim to use our results to improve training for current and future ISS flight controllers.

Clement, J. L.↗
NASA NTRS2008

MASSIM, the Milli-Arc-Second Structure Imager

The MASSIM (Milli-Arc-Second Structure Imager) mission will use a set of achromatic diffractive-refractive Fresnel lenses to achieve imaging in the X-ray band with unprecedented angular resolution. It has been proposed for study within the context of NASA's "Astrophysics Strategic Mission Concept Studies" program. Lenses on an optics spacecraft will focus 5-11 keV X-rays onto detectors on a second spacecraft flying in formation 1000 km away. It will have a point-source sensitivity comparable with that of the current generation of major X-ray observatories (Chandra, XMM-Newton) but an angular resolution some three orders of magnitude better. MASSIM is optimized for the study of jets and other phenomena that occur in the immediate vicinity of black holes and neutron stars. It can also be used for studying other phenomena on the milli-arc-second scale, such as those involving proto-stars, the surfaces and surroundings of nearby active stars and interacting winds.

Skinner, Gerry↗
NASA NTRS2008

Development Status of the CECE Cryogenic Deep Throttling Demonstrator Engine

As one of the first technology development programs awarded by NASA under the U.S. Space Exploration Policy (USSEP), the Pratt & Whitney Rocketdyne (PWR) Deep Throttling, Common Extensible Cryogenic Engine (CECE) program was selected by NASA in November 2004 to begin technology development and demonstration toward a deep throttling, cryogenic engine supporting ongoing trade studies for NASA's Lunar Lander descent stage. The CECE program leverages the maturity and previous investment of a flight-proven hydrogen/oxygen expander cycle engine, the PWR RLI0, to develop and demonstrate an unprecedented combination of reliability, safety, durability, throttlability, and restart capabilities in a high-energy, cryogenic engine. The testbed selected for the deep throttling demonstration phases of this program was a minimally modified RL10 engine, allowing for maximum current production engine commonality and extensibility with minimum program cost. Two series of demonstrator engine tests, the first in April-May 2006 and the second in March-April 2007, have demonstrated in excess of 10:1 throttling of the hydrogen/oxygen expander cycle engine. Both test series have explored a combustion instability ("chug") environment at low throttled power levels. These tests have provided an early demonstration of an enabling cryogenic propulsion concept with invaluable system-level technology data acquisition toward design and development risk mitigation for future CECE Demonstrator engine tests.

Source record↗
NASA NTRS2008

Pulsars and Acceleration Sites

Rotation-powered pulsars are excellent laboratories for the studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. But even forty years after their discovery, we still do not understand their pulsed emission at any wavelength. I will review both the basic physics of pulsars as well as the latest developments in understanding their high-energy emission. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. Fortunately the Gamma-Ray Large Area Space Telescope (GLAST), with launch in May 2008 will detect many new gamma-ray pulsars and test the predictions of these models with unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 300 GeV.

Harding, Alice↗
NASA NTRS2007

HST/ACS Narrowband Imaging of the Kepler Supernova Remnant

We present narrowband images of the Kepler supernova remnant obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope. The images, with an angular resolution of 0.05" reveal the structure of the emitting gas in unprecedented detail. Radiative and nonradiative shocks are found in close proximity, unresolvable in gro~md-based spectra, indicating that the pre-shock medium is highly clumped. The ionization structure, traced by differences in the [0 111] to [N 11] flux ratio, varies on subarcsecond scales. The variation is due to 110th differences in shock velocity as well as gradients in the evolutionary stage of the shocks. A pro~llinent complex of knots protruding beyond the boundary of the ren~nallt in the northwest is found to consist of bright radiative knots, collected by arcuate nonradiative filaments. Based on the coincidence of the optical emission with a bright isolated knot of X-ray emission, we infer that this feature is due to a Rayleigh-Taylor finger that formed at the contact discontinuity and overtook the primary blast wave.

Sankrit, Ravi↗
NASA NTRS2008

Five-Year Wilkinson Microwave Anisotropy Probe (WMAP)Observations: Beam Maps and Window Functions

Cosmology and other scientific results from the WMAP mission require an accurate knowledge of the beam patterns in flight. While the degree of beam knowledge for the WMAP one-year and three-year results was unprecedented for a CMB experiment, we have significantly improved the beam determination as part of the five-year data release. Physical optics fits are done on both the A and the B sides for the first time. The cutoff scale of the fitted distortions on the primary mirror is reduced by a factor of approximately 2 from previous analyses. These changes enable an improvement in the hybridization of Jupiter data with beam models, which is optimized with respect to error in the main beam solid angle. An increase in main-beam solid angle of approximately 1% is found for the V2 and W1-W4 differencing assemblies. Although the five-year results are statistically consistent with previous ones, the errors in the five-year beam transfer functions are reduced by a factor of approximately 2 as compared to the three-year analysis. We present radiometry of the planet Jupiter as a test of the beam consistency and as a calibration standard; for an individual differencing assembly. errors in the measured disk temperature are approximately 0.5%.

Hill, R.S.↗
NASA NTRS2008

Changing Characteristics of Jupiter's Little Red Spot

The Little Red Spot (LRS) in Jupiter's atmosphere was investigated in unprecedented detail by the New Horizons spacecraft together with the Hubble Space Telescope (HST) and the Very Large Telescope (VLT). The LRS and the larger Great Red Spot (GRS) of Jupiter are the largest known atmospheric storms in the solar system. Originally a white oval, the LRS formed from the mergers of three smaller storms in 1998 and 2000 and became as red as the GRS between 2005 and 2006. Here we show that circulation and wind speeds in the LRS have increased substantially since the Voyager and Galileo eras when the oval was white. The maximum tangential velocity of the LRS is now 172 +/- 18 m/s, close to the highest values ever seen in the GRS, which has also evolved both in size and maximum wind speed. The cloud top altitudes of the GRS and LRS are similar, both storms extending much higher in the atmosphere than other Jovian anticyclonic systems. The similarities in wind speeds, cloud morphology, and coloring suggest a common dynamical mechanism explains the reddening of the two largest anticyclonic systems on Jupiter. These storms will not be observed again from close range until at least 2016.

Cheng, A. F.↗
NASA NTRS2008

Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Likelihoods and Parameters from the WMAP Data

The Wilkinson Microwave Anisotropy Probe (WMAP), launched in 2001, has mapped out the Cosmic Microwave Background with unprecedented accuracy over the whole sky. Its observations have led to the establishment of a simple concordance cosmological model for the contents and evolution of the universe, consistent with virtually all other astronomical measurements. The WMAP first-year and three-year data have allowed us to place strong constraints on the parameters describing the ACDM model. a flat universe filled with baryons, cold dark matter, neutrinos. and a cosmological constant. with initial fluctuations described by nearly scale-invariant power law fluctuations, as well as placing limits on extensions to this simple model (Spergel et al. 2003. 2007). With all-sky measurements of the polarization anisotropy (Kogut et al. 2003; Page et al. 2007), two orders of magnitude smaller than the intensity fluctuations. WMAP has not only given us an additional picture of the universe as it transitioned from ionized to neutral at redshift z approx.1100. but also an observation of the later reionization of the universe by the first stars. In this paper we present cosmological constraints from WMAP alone. for both the ACDM model and a set of possible extensions. We also consider tlle consistency of WMAP constraints with other recent astronomical observations. This is one of seven five-year WMAP papers. Hinshaw et al. (2008) describe the data processing and basic results. Hill et al. (2008) present new beam models arid window functions, Gold et al. (2008) describe the emission from Galactic foregrounds, and Wright et al. (2008) the emission from extra-Galactic point sources. The angular power spectra are described in Nolta et al. (2008), and Komatsu et al. (2008) present and interpret cosmological constraints based on combining WMAP with other data. WMAP observations are used to produce full-sky maps of the CMB in five frequency bands centered at 23, 33, 41, 61, and 94 GHz (Hinshaw et al. 2008). With five years of data, we are now able to place better limits on the ACDM model. as well as to move beyond it to test the composition of the universe. details of reionization. sub-dominant components, characteristics of inflation, and primordial fluctuations. We have more than doubled the amount of polarized data used for cosmological analysis. allowing a better measure of the large-scale E-mode signal (Nolta et al. 2008). To this end we describe an alternative way to remove Galactic foregrounds from low resolution polarization maps in which Galactic emission is marginalized over, providing a cross-check of our results. With longer integration we also better probe the second and third acoustic peaks in the temperature angular power spectrum, and have many more year-to-year difference maps available for cross-checking systematic effects (Hinshaw et al. 2008).

Dunkey, J.↗
NASA NTRS2007

CALISTO: A Cryogenic Far-Infrared/Submillimeter Observatory

We present a design for a cryogenically cooled large aperture telescope for far-infrared astronomy in the wavelength range 30 micrometers to 300 micrometers. The Cryogenic Aperture Large Infrared Space Telescope Observatory, or CALISTO, is based on an off-axis Gregorian telescope having a 4 m by 6 m primary reflector. This can be launched using an Atlas V 511, with the only optical deployment required being a simple hinged rotation of the secondary reflector. The off-axis design, which includes a cold stop, offers exceptionally good performance in terms of high efficiency and minimum coupling of radiation incident from angles far off the direction of maximum response. This means that strong astronomical sources, such as the Milky Way and zodiacal dust in the plane of the solar system, add very little to the background. The entire optical system is cooled to 4 K to make its emission less than even this low level of astronomical emission. Assuming that detector technology can be improved to the point where detector noise is less than that of the astronomical background, we anticipate unprecedented low values of system noise equivalent power, in the vicinity of 10(exp -19) WHz(exp -0.5), through CALISTO's operating range. This will enable a variety of new astronomical investigations ranging from studies of objects in the outer solar system to tracing the evolution of galaxies in the universe throughout cosmic time.

Cryogenic Aperture Large Infrared Space Telescope ↗
NASA NTRS2007

SIM Planetquest Science and Technology: A Status Report

Optical interferometry will open new vistas for astronomy over the next decade. The Space Interferometry Mission (SIM-PlanetQuest), operating unfettered by the Earth's atmosphere, will offer unprecedented astrometric precision that promises the discovery of Earth-analog extra-solar planets as well as a wealth of important astrophysics. Results from SIM will permit the determination of stellar masses to accuracies of 2% or better for objects ranging from brown dwarfs through main sequence stars to evolved white dwarfs, neutron stars, and black holes. Studies of star clusters will yield age determinations and internal dynamics. Microlensing measurements will present the mass spectrum of the Milky Way internal to the Sun while proper motion surveys will show the Sun's orbital radius and speed. Studies of the Galaxy's halo component and companion dwarf galaxies permit the determination of the Milky Way's mass distribution, including its Dark Matter component and the mass distribution and Dark Matter component of the Local Group. Cosmology benefits from precision (1-2%) determination of distances to Cepheid and RR Lyrae standard candles. The emission mechanism of supermassive black holes will be investigated. Finally, radio and optical celestial reference frames will be tied together by an improvement of two orders of magnitude. Optical interferometers present severe technological challenges. The Jet Propulsion Laboratory, with the support of Lockheed Martin Advanced Technology Center (LM ATC) and Northrop Grumman Space Technology (NGST), has addressed these challenges with a technology development program that is now complete. The requirements for SIM have been satisfied, based on outside peer review, using a series of laboratory tests and appropriate computer simulations: laser metrology systems perform with 10 picometer precision; mechanical vibrations have been controlled to nanometers, demonstrating orders of magnitude disturbance rejection; and knowledge of component positions throughout the whole test assembly has been demonstrated to the required picometer level. Technology transfer to the SIM flight team is now well along.

astrometry↗