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Miller, J. A.

Publications and source records attributed to Miller, J. A..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

A Comparison of Snow Depth on Sea Ice Retrievals Using Airborne Altimeters and an AMSR-E Simulator

A comparison of snow depths on sea ice was made using airborne altimeters and an Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) simulator. The data were collected during the March 2006 National Aeronautics and Space Administration (NASA) Arctic field campaign utilizing the NASA P-3B aircraft. The campaign consisted of an initial series of coordinated surface and aircraft measurements over Elson Lagoon, Alaska and adjacent seas followed by a series of large-scale (100 km ? 50 km) coordinated aircraft and AMSR-E snow depth measurements over portions of the Chukchi and Beaufort seas. This paper focuses on the latter part of the campaign. The P-3B aircraft carried the University of Colorado Polarimetric Scanning Radiometer (PSR-A), the NASA Wallops Airborne Topographic Mapper (ATM) lidar altimeter, and the University of Kansas Delay-Doppler (D2P) radar altimeter. The PSR-A was used as an AMSR-E simulator, whereas the ATM and D2P altimeters were used in combination to provide an independent estimate of snow depth. Results of a comparison between the altimeter-derived snow depths and the equivalent AMSR-E snow depths using PSR-A brightness temperatures calibrated relative to AMSR-E are presented. Data collected over a frozen coastal polynya were used to intercalibrate the ATM and D2P altimeters before estimating an altimeter snow depth. Results show that the mean difference between the PSR and altimeter snow depths is -2.4 cm (PSR minus altimeter) with a standard deviation of 7.7 cm. The RMS difference is 8.0 cm. The overall correlation between the two snow depth data sets is 0.59.

Cavalieri, D. J.↗
NASA NTRS1990

Ion and relativistic electron transport in solar flares

Recent models for the ion and relativistic electron transport in solar flare magnetic loops are reviewed, focusing on the ways in which the models handle loop structure, particle acceleration, and particle transport. Results are presented from Monte Carlo simulations of ion and relativistic ion transport. Consideration is given to results concerning the depth distributions of gamma-ray production, the attenuation of gamma-ray lines, the time dependences of the various emissions and the angular distribution of the bremsstrahlung.

Ramaty, R.↗
NASA NTRS1990

Solar accelerated particles - Comparisons of abundances and energy spectra from particle and gamma-ray observations

Gamma-ray observations of the April 27, 1981 flare have been used to derive elemental abundances of both the ambient gas and the accelerated particle which interact with this gas to produce gamma rays. The results show that the abundances of the accelerated particles which produce the gamma rays are much more consistent with first-class particle abundances than with large proton-flare abundances. Observed bremsstrahlung spectral from 16 flares are compared with calculated bremsstrahlung spectra. It is concluded that the electrons observed in interplanetary space and the electrons responsible for gamma-ray production cannot be drawn from the same accelerated particle population without the former being affected by reacceleration or energy-dependent escape.

Ramaty, R.↗
NASA NTRS1983

High-speed machining of Space Shuttle External Tank (ET) panels

Potential production rates and project cost savings achieved by converting the conventional machining process in manufacturing shuttle external tank panels to high speed machining (HSM) techniques were studied. Savings were projected from the comparison of current production rates with HSM rates and with rates attainable on new conventional machines. The HSM estimates were also based on rates attainable by retrofitting existing conventional equipment with high speed spindle motors and rates attainable using new state of the art machines designed and built for HSM.

Miller, J. A.↗
NASA NTRS1983

High-Speed Machining (HSM) of Space Shuttle External Tank (ET) panels

The External Fuel Tank (ET) of the Space Shuttle is not recovered after launch and a new one must be provided for each launch. Currently, the external ""skin'' panels of the tank are produced by machining from solid wrought 2219-T87 aluminum plate stock approximately 1-3/4 inch thick. The reduction of costs in producing External Fuel Tank panels is obviously of increasing production rates and decreasing costs of the panels through the application of high-speed machining (HSM) techniques was conducted.

Miller, J. A.↗
NASA NTRS1982

High-speed machining of space shuttle External Tank (ET) panels

The applicability to and advantages of the high-speed machining process for the production of Space Shuttle external tank panels by physically machining selected sample portions of an external tank panel were investigated. The panel sample configuration was selected, and potential high speed milling procedures identified. An 8 foot long panel was machined and the milling demonstration is described in detail.

Miller, J. A.↗
NASA NTRS1979

Guidance system for a roving vehicle

Computer controlled guidance system for semiautonomous robot guides robot in incompletely defined environment. System operates in real time avoiding obstacles detected by "stereo television and laser range finder eyes."

Miller, J. A.↗
NASA NTRS1977

A discrete adaptive guidance system for a roving vehicle

An adaptive guidance technique which provides a self-correcting path following capability in an environment sensitive semi-autonomous roving robot is described. A real-time maneuver planning function performs tradeoffs between speed, magnitude of expected deviations and accelerations to best satisfy the design goals of vehicle safety and reliability, subsystem autonomy, performance accuracy and operational efficiency. The appropriate combination of maneuver parameters is selected through an iterative process using knowledge of vehicle performance characteristics, environmental model updates and vehicle state

Miller, J. A.↗
NASA NTRS1975

Demonstration of optical navigation measurements on Mariner 10

An experiment was performed on the Mariner 10 Venus/Mercury mission to assess the performance of the onboard television cameras and ground-based software used in the optical navigation measurement system. The elements of the system, calibration, and distortion are considered. The navigation technique requires detection of stars in the same field of view as the target body. The star detection capability is discussed with reference to required threshold, calibration factors, standard conditions, camera sensitivity, response uniformity, and the effect of image smearing. Tests conducted during the Mariner 10 encounters with Mercury demonstrated that a large bright planet can be imaged simultaneously with faint stars to provide accurate navigation data. Improvements are suggested in the system for the Mariner Jupiter/Saturn 1977 and later missions.

Stanton, R. H.↗