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NASA NTRS1998

The Kepler Mission: Search for Habitable Planets

Detecting extrasolar terrestrial planets orbiting main-sequence stars is of great interest and importance. Current ground-based methods are only capable of detecting objects about the size or mass of Jupiter or larger. The difficulties encountered with direct imaging of Earth-size planets from space are expected to be resolved in the next twenty years. Spacebased photometry of planetary transits is currently the only viable method for detection of terrestrial planets (30-600 times less massive than Jupiter). This method searches the extended solar neighborhood, providing a statistically large sample and the detailed characteristics of each individual case. A robust concept has been developed and proposed as a Discovery-class mission. Its capabilities and strengths are presented.

Borucki, William↗

NASA NTRS2009

Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in the planning stages.

Reverberant acoustic field↗

NASA NTRS1995

Passive measurement and interpretation of polarized microwave brightness temperatures

The goal of this project is to develop satellite-based observational techniques for measuring both oceanic and atmospheric variables using passive polarimetric radiometry. Polarimetric radiometry offers a potential alternative to radar scatterometry in observing global ocean surface wind direction from satellites. Polarimetric radiometry might also provide a means of detecting cell-top ice in convective storms by virtue of the polarizing properties of oriented ice particles, and thus facilitate estimation of the phase of the storm. The project focuses on the development of polarimetric microwave radiometers using digital cross-correlators for obtaining precise measurements of all four Stokes' parameters. As part of the project a unique four-band polarimetric imaging radiometer, the Polar Scanning Radiometer (PSR), is being designed for use on the NASA DC-8 aircraft. In addition to providing an aircraft-based demonstration of digital correlation technology the PSR will significantly enhance the microwave imaging capability of the existing suite of DC-8 instruments. During the first grant year excellent progress has been made in the following areas: (1) demonstrating digital correlation radiometry, (2) fabricating aircraft-qualified correlators for use in the PSR, and (3) modeling observed SSM/I brightness signatures of ocean wind direction.

Gasiewski, A. J.↗

NASA NTRS2012

Analysis of Organic Molecules Extracted from Mars Analogues and Influence of Their Mineralogy Using N-Methyl-N-(tert-butyldimethylsilyl)Trifluoroacetamide Derivatization Coupled with Gas Chromatography Mass Spectrometry in Preparation for the Sample Analysis at Mars Derivatization Experiment on the Mars Science Laboratory Mission

The search for complex organic molecules on Mars, including important biomolecules such as amino acids and carboxylic acids will require a chemical extraction and derivatization step to transform these organic compounds into species that are sufficiently volatile to be detected by gas chromatography mass spectrometry (GCMS). We have developed, a one-pot extraction and chemical derivatization protocol using N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) and dimethylformamide (DMF) for the Sample Analysis at Mars (SAM) experiment on the Mars Science Laboratory (MSL). The temperature and duration the derivatization reaction, pre-concentration of chemical derivatives, and gas chromatographic separation parameters have been optimized under SAM instrument design constraints. MTBSTFA/DMF extraction and derivatization at 300 C for several minutes of a variety of terrestrial Mars analogue materials facilitated the detection of amino acids and carboxylic acids in a surface soil sample collected from the Atacama Desert and a carbonate-rich stromatolite sample from Svalbard. However, the rapid reaction of MTBSTFA with water in several analogue materials that contained high abundances of hydrated minerals and the possible deactivation of derivatized compounds by iron oxides, as detected by XRD/XRF using the CheMin field unit Terra, proved to be highly problematic for the direct extraction of organics using MTBSTFA, The combination of pyrolysis and two different chemical derivatization methods employed by SAM should enable a wide range of organic compounds to be detected by GCMS if present on Mars,

Stalport, F.↗

NASA NTRS2014

Detecting Super-Thin Clouds With Polarized Light

We report a novel method for detecting cloud particles in the atmosphere. Solar radiation backscattered from clouds is studied with both satellite data and a radiative transfer model. A distinct feature is found in the angle of linear polarization of solar radiation that is backscattered from clouds. The dominant backscattered electric field from the clear-sky Earth-atmosphere system is nearly parallel to the Earth surface. However, when clouds are present, this electric field can rotate significantly away from the parallel direction. Model results demonstrate that this polarization feature can be used to detect super-thin cirrus clouds having an optical depth of only ~0.06 and super-thin liquid water clouds having an optical depth of only ~0.01. Such clouds are too thin to be sensed using any current passive satellite instruments.

Sun, Wenbo↗

NASA NTRS2014

Detecting Super-Thin Clouds with Polarized Sunlight

Aerosols and particles↗

NASA NTRS1970

Remote sensing for defining aquifers in glacial drift

Investigations were undertaken to determine the properties of shallow aquifers and related features that influence electromagnetic energy, to determine how these properties can be detected remotely, and to establish remote sensing procedures for aiding in ground water mapping. The direct influence of aquifier characteristics on surface thermal contrasts is discussed. Conclusions reached for late summer, predawn missions were: (1) Dynamic thermal changes near the surface can be used for thermal infrared sensing to detect shallow aquifers in glacial drift. (2) Under ideal conditions, surface temperatures may be used to predict certain features related to the occurrence of shallow aquifers. (3) The timing of missions and the optimum meteorological conditions occurring prior to and during the mission are critical for night thermal missions. (4) Repetitive flights made under variable conditions provide additional evidence to verify the occurrence of shallow aquifers. (5) Imagery from this investigation, along with ERTS-simulated imagery, indicates the feasibility of applying ERTS A and B data to reconnaissance studies for detection of shallow aquifers.

Myers, V. I.↗

NASA NTRS2014

Impact of Acoustic Standing Waves on Structural Responses

For several decades large reverberant chambers and most recently direct field acoustic testing have been used in the aerospace industry to test larger structures with low surface densities such as solar arrays and reflectors to qualify them and to detect faults in the design and fabrication. It has been reported that in reverberant chamber and direct acoustic testing, standing acoustic modes may strongly couple with the fundamental structural modes of the test hardware (Reference 1). In this paper results from a recent reverberant chamber acoustic test of a composite reflector are discussed. These results provide further convincing evidence of the acoustic standing wave and structural modes coupling phenomenon. The purpose of this paper is to alert test organizations to this phenomenon so that they can account for the potential increase in structural responses and ensure that flight hardware undergoes safe testing. An understanding of the coupling phenomenon may also help minimize the over and/or under testing that could pose un-anticipated structural and flight qualification issues.

Reverberant acoustic field↗

NASA NTRS1998

GPS, Earthquakes, the Ionosphere, and the Space Shuttle

Sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce infrasonic pressure waves in the atmosphere. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these acoustic waves induce variations of the ionospheric electron density. The Global Positioning System provides a way of directly measuring the Total Electron Content in the ionosphere and, therefore. of detecting such perturbations in the upper atmosphere. In this work, we demonstrate the capabilities of the GPS technique to detect ionospheric perturbations caused by the January 17. 1994, M (sub w) =6.7, Northridge earthquake and the STS-58 Space Shuttle ascent. In both cases, we observe a perturbation of the ionospheric electron density lasting for about 30 m, with periods less than 10 m. The perturbation is complex and shows two sub-events separated by about 15 m. The phase velocities and waveform characteristics of the two sub-events lead us to interpret the first arrival as the direct propagation of 2 free wave, followed by oscillatory guided waves propagating along horizontal atmospheric interfaces at 120 km altitude and below.

Calais, Eric↗

NASA NTRS2015

Lightning Imaging Sensor (LIS) for the International Space Station (ISS): Mission Description and Science Goals

In recent years, the NASA Marshall Space Flight Center, the University of Alabama in Huntsville, and their partners have developed and demonstrated space-based lightning observations as an effective remote sensing tool for Earth science research and applications. The Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) continues to acquire global observations of total (i.e., intracloud and cloud-to-ground) lightning after 17 years on-orbit. However, TRMM is now low on fuel, so this mission will soon be completed. As a follow on to this mission, a space-qualified LIS built as the flight spare for TRMM has been selected for flight as a science mission on the International Space Station (ISS). The ISS LIS will be flown as a hosted payload on the Department of Defense Space Test Program (STP) H5 mission, which has a January 2016 baseline launch date aboard a SpaceX launch vehicle for a 2-4 year or longer mission. The LIS measures the amount, rate, and radiant energy of total lightning over the Earth. More specifically, it measures lightning during both day and night, with storm scale resolution (approx. 4 km), millisecond timing, and high, uniform detection efficiency, without any land-ocean bias. Lightning is a direct and most impressive response to intense atmospheric convection. It has been found that lightning measured by LIS can be quantitatively related to thunderstorm and other geophysical processes. Therefore, the ISS LIS lightning observations will continue to provide important gap-filling inputs to pressing Earth system science issues across a broad range of disciplines, including weather, climate, atmospheric chemistry, and lightning physics. A unique contribution from the ISS platform will be the availability of real-time lightning data, especially valuable for operational applications over data sparse regions such as the oceans. The ISS platform will also uniquely enable LIS to provide simultaneous and complementary observations with other ISS payloads such as the European Space Agency's Atmosphere-Space Interaction Monitor (ASIM) that will be exploring the connection between thunderstorms and lightning with terrestrial gamma-ray flashes (TGFs) and the Japan Aerospace Exploration Agency's Global LIghtning and Sprites MeasurementS (GLIMS) with its focus on global lightning and sprite connections. Another important function of the ISS LIS will be to provide cross-sensor calibration/validation with a number of other payloads, including the TRMM LIS and the next generation geostationary lightning mappers such as the GOES-R Geostationary Lightning Mapper (GLM) and Meteosat Third Generation Lightning Imager (MTG LI), as well as with ground-based lightning detection systems. These inter-calibrations will improve the long term climate monitoring record provided by all these systems. Finally, the ISS LIS will extend the time-series climate record of LIS lightning observations and expand the latitudinal coverage of LIS lightning to the climate significant upper middle-latitudes.

Blakeslee, R. J.↗

NASA NTRS1975

Saturn radio emission near 1 MHz

Radio emissions from the direction of Saturn are analyzed which were observed by IMP-6 at 15 frequencies between 375 and 2200 kHz from April 1971 to October 1972. The radio bursts are identified in the IMP-6 data by a phase analysis of the spin-modulated signal from the spacecraft's dipole antenna, and approximately 12 storms are isolated whose occurrence corresponded to times when the spacecraft had an unobstructed view in the direction of Saturn. The spectral character of the radiation is found to be analogous to that of Jupiter, and a power-spectral analysis of the storm occurrence times indicates a weak periodicity for some of the observing frequencies. The Saturnian emission most similar to Jupiter's decametric emission is found to be strongest at 1100 kHz with a bandwidth of about 1000 kHz. A secondary spectral peak may exist at 400 kHz, which is similar to that observed for Earth and Jupiter. The detection of this nonthermal radio emission is shown to be the first direct evidence for the existence of a Saturnian magnetic field containing energetic particles.

Brown, L. W.↗

NASA NTRS2003

The Rondonia Lightning Detection Network: Network Description, Science Objectives, Data Processing Archival/Methodology, and Results

A four station Advanced Lightning Direction Finder (ALDF) network was established in the state of Rondonia in western Brazil in 1999 through a collaboration of U.S. and Brazilian participants from NASA, INPE, INMET, and various universities. The network utilizes ALDF IMPACT (Improved Accuracy from Combined Technology) sensors to provide cloud-to-ground lightning observations (i.e., stroke/flash locations, signal amplitude, and polarity) using both time-of- arrival and magnetic direction finding techniques. The observations are collected, processed and archived at a central site in Brasilia and at the NASA/Marshall Space Flight Center in Huntsville, Alabama. Initial, non-quality assured quick-look results are made available in near real-time over the Internet. The network, which is still operational, was deployed to provide ground truth data for the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite that was launched in November 1997. The measurements are also being used to investigate the relationship between the electrical, microphysical and kinematic properties of tropical convection. In addition, the long-time series observations produced by this network will help establish a regional lightning climatological database, supplementing other databases in Brazil that already exist or may soon be implemented. Analytic inversion algorithms developed at the NASA/Marshall Space Flight Center have been applied to the Rondonian ALDF lightning observations to obtain site error corrections and improved location retrievals. The data will also be corrected for the network detection efficiency. The processing methodology and the results from the analysis of four years of network operations will be presented.

Blakeslee, R. J.↗

NASA NTRS2012

The Influence of Mineralogy on Recovering Organic Acids from Mars Analogue Materials Using the One-Pot Derivatization Experiment on the Sample Analysis at Mars(SAM) Instrument Suite

The search for complex organic molecules on Mars, including important biomolecules such as amino acids and carboxylic acids, will require a chemical extraction and a derivatization step to transform these organic compounds into species that are sufficiently volatile to be detected by gas chromatography mass spectrometry (GCMS). We have developed a ''one-pot'' extraction and chemical derivatization protocol using N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) and dimethylformamide (DMF) for the Sample Analysis at Mars (SAM) experiment instrument suite on NASA's the Mars Science Laboratory (MSL) mission. The temperature and duration of the derivatization reaction, pre-concentration of chemical derivatives, and gas chromatographic separation parameters have been optimized under SAM instrument design constraints. MTBSTFA/DMF extraction and derivatization at 300 1C for several minutes of a variety of terrestrial Mars analog materials facilitated the detection of amino acids and carboxylic acids in a surface soil sample collected from the Atacama Desert and a carbonate-rich stromatolite sample from Svalbard. However, the rapid reaction of MTBSTFA with water in several analog materials that contained high abundances of hydrated minerals, and the possible deactivation of derivatized compounds by iron oxides, as detected by XRD/XRF using the CheMin field unit Terra, proved to be highly problematic for the direct extraction of organics using MTBSTFA. The combination of pyrolysis and two different wet-chemical derivatization methods employed by SAM should enable a wide range of organic compounds to be detected by GCMS if present on Mars.

MSL↗

NASA NTRS1985

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Test act system validation

The primary objective of the Test Active Control Technology (ACT) System laboratory tests was to verify and validate the system concept, hardware, and software. The initial lab tests were open loop hardware tests of the Test ACT System as designed and built. During the course of the testing, minor problems were uncovered and corrected. Major software tests were run. The initial software testing was also open loop. These tests examined pitch control laws, wing load alleviation, signal selection/fault detection (SSFD), and output management. The Test ACT System was modified to interface with the direct drive valve (DDV) modules. The initial testing identified problem areas with DDV nonlinearities, valve friction induced limit cycling, DDV control loop instability, and channel command mismatch. The other DDV issue investigated was the ability to detect and isolate failures. Some simple schemes for failure detection were tested but were not completely satisfactory. The Test ACT System architecture continues to appear promising for ACT/FBW applications in systems that must be immune to worst case generic digital faults, and be able to tolerate two sequential nongeneric faults with no reduction in performance. The challenge in such an implementation would be to keep the analog element sufficiently simple to achieve the necessary reliability.

Source record↗

NASA NTRS2003

Passive Fetal Heart Monitoring System

A fetal heart monitoring system and method for detecting and processing acoustic fetal heart signals transmitted by different signal transmission modes. One signal transmission mode, the direct contact mode, occurs in a first frequency band when the fetus is in direct contact with the maternal abdominal wall. Another signal transmission mode, the fluid propagation mode, occurs in a second frequency band when the fetus is in a recessed position with no direct contact with the maternal abdominal wall. The second frequency band is relatively higher than the first frequency band. The fetal heart monitoring system and method detect and process acoustic fetal heart signals that are in the first frequency band and in the second frequency band.

Zuckerwar, Allan J.↗

NASA NTRS2010

Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

LAT(LARGE AREA TELESCOPE)↗

NASA NTRS1988

Detecting Space Dust Particles

Technique records times specific craters formed in targets exposed in space and permits determination of direction in which impacting particles traveled at times of impacts. MOS capacitor is short-circuited by impact of particle striking at high speed. After recovery of targets from space, compositions of impacting particles established through post-flight laboratory analyses of residual materials in craters. On earth technique has industrial and military uses in detection of fragments driven by explosions. Studies of orbital dynamics of particles produced by solid-propellant rocket-motor firings in space made using technique.

Kinard, William H.↗

NASA NTRS2013

Fast, Large-Area, Wide-Bandgap UV Photodetector for Cherenkov Light Detection

Due to limited resources available for power and space for payloads, miniaturizing and integrating instrumentation is a high priority for addressing the challenges of manned and unmanned deep space missions to high Earth orbit (HEO), near Earth objects (NEOs), Lunar and Martian orbits and surfaces, and outer planetary systems, as well as improvements to high-altitude aircraft safety. New, robust, and compact detectors allow future instrumentation packages more options in satisfying specific mission goals. A solid-state ultraviolet (UV) detector was developed with a theoretical fast response time and large detection area intended for application to Cherenkov detectors. The detector is based on the wide-bandgap semiconductor zinc oxide (ZnO), which in a bridge circuit can detect small, fast pulses of UV light like those required for Cherenkov detectors. The goal is to replace the role of photomultiplier tubes in Cherenkov detectors with these solid-state devices, saving on size, weight, and required power. For improving detection geometry, a spherical detector to measure high atomic number and energy (HZE) ions from any direction has been patented as part of a larger space radiation detector system. The detector will require the development of solid-state UV photodetectors fast enough (2 ns response time or better) to detect the shockwave of Cherenkov light emitted as the ions pass through a quartz, sapphire, or acrylic ball. The detector must be small enough to fit in the detector system structure, but have an active area large enough to capture enough Cherenkov light from the sphere. The detector is fabricated on bulk single-crystal undoped ZnO. Inter - digitated finger electrodes and contact pads are patterned via photolithography, and formed by sputtered metal of silver, platinum, or other high-conductivity metal.

Wrbanek, John D.↗