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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Digital test signal generation: An accurate SNR calibration approach for the DSN

In support of the on-going automation of the Deep Space Network (DSN) a new method of generating analog test signals with accurate signal-to-noise ratio (SNR) is described. High accuracy is obtained by simultaneous generation of digital noise and signal spectra at the desired bandwidth (base-band or bandpass). The digital synthesis provides a test signal embedded in noise with the statistical properties of a stationary random process. Accuracy is dependent on test integration time and limited only by the system quantization noise (0.02 dB). The monitor and control as well as signal-processing programs reside in a personal computer (PC). Commands are transmitted to properly configure the specially designed high-speed digital hardware. The prototype can generate either two data channels modulated or not on a subcarrier, or one QPSK channel, or a residual carrier with one biphase data channel. The analog spectrum generated is on the DC to 10 MHz frequency range. These spectra may be up-converted to any desired frequency without loss on the characteristics of the SNR provided. Test results are presented.

Gutierrez-Luaces, Benito O.↗
NASA NTRS1994

Studies of Polar Mesosphere Summer Echoes by VHF radar and rocket probes

At radar frequencies in the range 50 MHz to 250 MHz, at times even to over 1 GHz, strong enhancements of scattering cross section occur between approximately equal to 80 km and approximately 95 km altitude in summer at high latitudes. These echoes, termed 'Polar Mesosphere Summer Echoes' (PMSE) have attracted considerable experimental effort. Observations of this phenomenon are reviewed in the context of atmospheric dynamics and of scattering processes. Recent rocket and radar measurements indicate that a partial reflection from a multitude of ion layers and constructive interference causes at least some of the PMSE. It is discussed which further observations are necessary and some possible practical consequences of PMSE are pointed out.

Hoppe, U. -P.↗
NASA NTRS1999

The LISA Mission Design

The proposed Laser Interferometer Space Antenna (LISA) is designed to observe gravitational radiation from galactic binaries and massive black holes in other galaxies. LISA will observe waves in the frequency range 0.1 mHz to 1 Hz, which can never be observed on Earth due to background noise. The three LISA spacecraft will be located at the vertices of an equilateral triangle with side length 5 million km. The orbits are chosen so that the triangle formation trails the Earth by 20 degrees. Each spacecraft will contain two independent instruments containing a proof mass, laser and 30 cm diameter telescope for the transmission and reception of laser signals. Two independent Michelson interferometers will be formed, allowing both polarizations of gravitational waves to be detected. The observed signals will yield unique information about the formation of massive black holes and the nature of gravity in the high-field limit.

Folkner, W. M.↗
NASA NTRS1998

Control of Jovian Radio Emission by Ganymede

Galileo has been in orbit around Jupiter since December 1995. We present the results of a survey of the data for the frequency range 3.2 MHz to 5.6 MHz, the low-frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon Io is well-known, we report that a small but significant portion of low-frequency DAM emission is seen to be correlated with the orbital phase of Ganymede. This result is in agreement with other recent results indicating a significant interaction of the magnetosphere of Ganymede with that of Jupiter.

Menietti, J. D.↗
NASA NTRS2001

Control of Jovian Radio Emission by Callisto

Galileo has been in orbit around Jupiter since December 1995 and a large database has been collected. We present the results of a survey of the plasma wave data for the frequency range 2.0 MHz to 5.6 MHz, the low frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon lo is well known, and Ganymede control has been more recently indicated, we report that a small but significant portion of DAM emission is seen to be correlated with the orbital phase of Callisto. While the occurrence rate of emission controlled by Ganymede and Callisto is considerably less than for lo, the power levels can be nearly the same. We estimate the power of the Callisto-dependent emission to be approx. 70% of the Io-dependent radio emission and about the same as the Ganymede-dependent radio emission. This result indicates an Alfven current system associated with Callisto, and thus a significant interaction of the magnetosphere of Callisto with that of Jupiter as is believed to exist for both lo and Ganymede.

Menietti, J. D.↗
NASA NTRS2002

Multi-Variable Model-Based Parameter Estimation Model for Antenna Radiation Pattern Prediction

A new procedure is presented to develop multi-variable model-based parameter estimation (MBPE) model to predict far field intensity of antenna. By performing MBPE model development procedure on a single variable at a time, the present method requires solution of smaller size matrices. The utility of the present method is demonstrated by determining far field intensity due to a dipole antenna over a frequency range of 100-1000 MHz and elevation angle range of 0-90 degrees.

Deshpande, Manohar D.↗
NASA NTRS2008

Performance of MEMS Silicon Oscillator, ASFLM1, under Wide Operating Temperature Range

Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to be offered as commercial-off-the-shelf (COTS) parts by a few companies [1-2]. These quartz-free, miniature silicon devices could compete with the traditional crystal oscillators in providing the timing (clock function) for many digital and analog electronic circuits. They provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [1-2]. In addition, they are encapsulated in compact lead-free packages, cover a wide frequency range (1 MHz to 125 MHz), and are specified, depending on the grade, for extended temperature operation from -40 C to +85 C. The small size of the MEMS oscillators along with their reliability and thermal stability make them candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an ABRACON Corporation MEMS silicon oscillator chip, type ASFLM1, under extreme temperatures.

Patterson, Richard L.↗
NASA NTRS2009

Assessment of Operation of EMK21 MEMS Silicon Oscillator Over Wide Temperature Range

Electronic control systems, data-acquisition instrumentation, and microprocessors require accurate timing signals for proper operation. Traditionally, ceramic resonators and crystal oscillators provided this clock function for the majority of these systems. Over the last few years, MEMS (Micro-Electro-Mechanical Systems) resonator-based oscillators began to surface as commercial-off-the-shelf (COTS) parts by a few companies. These quartz-free, miniature silicon devices could easily replace the traditional crystal oscillators in providing the timing/clock function for many digital and analog circuits. They are reported to provide stable output frequency, offer great tolerance to shock and vibration, and are immune to electro-static discharge [ 1-2]. In addition, they are encapsulated in compact lead-free packages and cover a wide frequency range (1 MHz to 125 MHz). The small size of the MEMS oscillators along with their thermal stability make them ideal candidates for use in space exploration missions. Limited data, however, exist on the performance and reliability of these devices under operation in applications where extreme temperatures or thermal cycling swings, which are typical of space missions, are encountered. This report presents the results of the work obtained on the evaluation of an Ecliptek Corporation MEMS silicon oscillator chip under extreme temperatures.

Patterson, Richard L.↗
NASA NTRS2016

Design Overview of the DM Radio Pathfinder Experiment

We introduce the DM Radio, a dual search for axion and hidden photon dark matter using a tunable superconducting lumped-element resonator. We discuss the prototype DM Radio Pathfinder experiment, which will probe hidden photons in the 500 peV (100 kHz)-50 neV (10 MHz) mass range. We detail the design of the various components: the LC resonant detector, the resonant frequency tuning procedure, the differential SQUID readout circuit, the shielding, and the cryogenic mounting structure. We present the current status of the pathfinder experiment and illustrate it's potential science reach in the context of the larger experimental program.

axion↗
NASA NTRS2017

A Piezoelectric Passive Wireless Sensor for Monitoring Strain

Interest in passive wireless sensing has grown over the past few decades to meet demands in structural health monitoring.(Deivasigamani et al., 2013; Wilson and Juarez, 2014) This work describes a passive wireless sensor for monitoring strain, which does not have an embedded battery or chip. Without an embedded battery, the passive wireless sensor has the potential to maintain its functionality over long periods in remote/harsh environments. This work also focuses on monitoring small strain (less than 1000 micro-ɛ). The wireless sensing system includes a reader unit, a coil-like transponder, and a sensing unit. It operates in the Megahertz (MHz) frequency range, which allows for a few centimeters of separation between the reader and sensing unit during measurements. The sensing unit is a strain-sensitive piezoelectric resonator that maximizes the energy efficiency at the resonance frequency, so it converts nanoscale mechanical variations to detectable differences in electrical signal. In response to an external loading, the piezoelectric sensor breaks from its original electromechanical equilibrium, and the resonant frequency shifts as the system reaches a new balanced equilibrium. In this work, the fixture of the sensing unit is a small, sticker-like package that converts the surface strain of a test material to measurable shifts in resonant frequencies. Furthermore, electromechanical modeling provides a lumped-parameter model of the system to describe and predict the measured wireless signals of the sensor. Detailed characterization demonstrates how this wireless sensor has resolution comparable to that of conventional wired strain sensors for monitoring small strain.

Zou, Xiyue↗
NASA NTRS2022

Measurement of SST and SSS Using Frequencies in the Range 0.3 – 2.0 GHz

Wide bandwidth radiometer systems that make measurements at multiple frequencies in the range 300 MHz to 2 GHz have been proposed to address parameters important for understanding issues in the cryosphere associated with climate change such as ice sheet thickness and temperature. It is also possible with such a system to retrieve sea surface salinity (SSS) which is important for understanding the impact of climate change on ocean circulation at high latitude. In contemporary sensors for retrieving SSS, such as SMOS and SMAP, sea surface temperature (SST), another parameter important for understanding ocean circulation and necessary in the retrieval of salinity, is treated as an ancillary parameter obtained from an independent source. However, both SSS and SST have peaks in sensitivity below 1 GHz; and it has been shown that measurements at multiple frequencies in this portion of the spectrum can take advantage of this peak in sensitivity to improve the accuracy of the retrieval of SSS. In this manuscript it will be shown that there is also the potential to retrieve SST and, in cold water, the possibility for improved accuracy over existing retrievals.

SST↗
NASA NTRS2023

Control and Non-Payload Communications Generation 7 Prototype Radio Flight Test Report

This report presents a description and test results of a seventh-generation prototype radio developed for Control and Non-Payload Communications (CNPC) between a ground-based pilot and an unmanned aircraft. Radios were prepared under a cooperative agreement between the NASA Glenn Research Center and Collins Aerospace (formerly Rockwell Collins, Inc.) and were used to support the development and validation of air-to-ground CNPC radio system standards. The CNPC radios operated in the 5,030- to 5,091-MHz frequency range. This report describes radio waveforms, laboratory testing, flight test systems, and flight test results.

Control and Non-Payload Communications↗
NASA NTRS2024

Interoperability Review of Wireless Hardware in Emergency Air-To-Ground Mesh Networks

The air-to-ground network has the goal of advancing the capabilities and versatility of communications in wildfire and emergency scenarios. To ensure compatibility and keep costs low for emergency services interoperability between hardware is an important step in development of the mesh network. For the purposes of this evaluation interoperability of hardware is described as the ability for hardware from different vendors to be interchangeable within the network with minimal initial setup and no functional change from an operator’s viewpoint. This report will also focus on the features and limitations in addition to the interoperability of the major wireless hardware systems core to the function of the proposed air-to-ground mesh network. The hardware systems involved are ADS-B receivers, 3GPP Sidelink devices, mesh radios, and commercial ISM band radios. For early testing the mesh radios will be in the 900 MHz frequency range using the DoodleLabs RM-1700-22W Mesh Rider Radio as the lab reference. This report will consider and categorize desirability of features, the amount of setup required before deployment, the effect on performance characteristics from nominal and maximum load, and the ability to interface with other vender devices.

Mesh Radio↗
NASA NTRS1990

Ultra-low-frequency wave power in the magnetotail lobes. I - Relation to substorm onsets and the auroral electrojet index

Time-series observations of the magnetotail-lobe magnetic field have been Fourier analyzed to compute the frequency-weighted energy density Pfz in the range 1-30 mHz. Pfz is generally observed in the range 0.0001-0.01 gamma-squared Hz with a mean value of 0.0012 during substorm growth phases and 0.001 in the comparison intervals. No strong correlation of Pfz is found with the auroral electrojet index in either set of intervals, but during substorm growth phases Pfz may vary by an order of magnitude over time scales of 30 min, with a tendency for higher power levels to occur later in the growth phase. Increases in Pfz precede by about 10 min localized expansive phase activity observed in individual magnetograms.

Smith, R. A.↗
NASA NTRS1974

Space shuttle electromagnetic environment experiment. Phase A: Definition study

A program is discussed which develops a concept for measuring the electromagnetic environment on earth with equipment on board an orbiting space shuttle. Earlier work on spaceborne measuring experiments is reviewed, and emissions to be expected are estimated using, in part, previously gathered data. General relations among system parameters are presented, followed by a proposal on spatial and frequency scanning concepts. The methods proposed include a nadir looking measurement with small lateral scan and a circularly scanned measurement looking tangent to the earth's surface at the horizon. Antenna requirements are given, assuming frequency coverage from 400 MHz to 40 GHz. For the low frequency range, 400-1000 MHz, a processed, thinned array is proposed which will be more fully analyzed in the next phase of the program. Preliminary hardware and data processing requirements are presented.

Haber, F.↗