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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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The radio Signal form the Galileo probe to the orbiter experienced attenuation due to ammonia in Jupiter's atmosphere during the probe descent.
The radio signal from the Galileo prove to the orbiter experienced attenuation due to ammonia in Jupiter's atmosphere during the probe descent.
Radio signals from air showers with electron sizes in the range 1 x 10 to the 7th power to 2 x 10 to the 9th power were detected at 50kHz, 170kHz, and 1,647kHz at large core distances in the Akeno square kilometers air-shower array. The field strength is higher than that expected from any mechanisms hitherto proposed.
The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approx. 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high- frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70/s, which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning.
Radio pulses generated by cosmic-ray air showers can be used to reconstruct key properties like the energy and depth of the electromagnetic component of cosmic-ray air showers. Radio detection threshold, influenced by natural and anthropogenic radio background, can be reduced through various techniques. In this work, we demonstrate that convolutional neural networks (CNNs) are an effective way to lower the threshold. We developed two CNNs: a classifier to distinguish radio signal waveforms from background noise and a denoiser to clean contaminated radio signals. Following the training and testing phases, we applied the networks to air-shower data triggered by scintillation detectors of the prototype station for the enhancement of IceTop, IceCube’s surface array at the South Pole. Over a four-month period, we identified 554 cosmic-ray events in coincidence with IceTop, approximately five times more compared to a reference method based on a cut on the signal-to-noise ratio. Comparisons with IceTop measurements of the same air showers confirmed that the CNNs reliably identified cosmic-ray radio pulses and outperformed the reference method. Additionally, we find that CNNs reduce the false-positive rate of air-shower candidates and effectively denoise radio waveforms, thereby improving the accuracy of the power and arrival time reconstruction of radio pulses.
Absolute value of signal power in weak radio signals is determined by computer-aided measurements. Equipment operates by averaging received signal over several-minute period and comparing average value with noise level of receiver previously calibrated.
Polarization measurements during scintillation of radio signals from transit iva satellite
Scintillation of radio transmissions from discoverer 38 to determine the existance and nature of diffracting e-region irregularities
Reception, analysis, and detection of radio signals from space
Deduction of reentry near wake plasma properties for Mercury and Gemini manned orbital spacecraft from radio signal attenuation data
A approach to the processing of space pulse radio signals, which makes it possible to achieve a high level of time resolution is proposed. The approach is based on the utilization of the Fourier transform of a radio pulse envelope in the interstellar medium effect. The conditions of applicability of the proposed method and the requirements for recording equipment are substantiated. Also indicated is the possibility of obtaining superresolution with the utilization of the given method of signal processing.
Morphology of ionosphere using radio signals from earth satellites
Auroral, polar cap, and sudden cosmic noise absorption estimates for 136 mc/s satellite radio signal
Signal attenuation, signal distortion, and radio noise generation due to ion engine exhaust beam
The power spectrum of phase modulation imposed upon satellite radio signals by the inhomogeneous F-region of the ionosphere (100 - 500 km) was studied. Tapes of the S-66 Beacon B Satellite recorded during the period 1964 - 1966 were processed to yield or record the frequency of modulation induced on the signals by ionospheric dispersion. This modulation is produced from the sweeping across the receiving station as the satellite transits of the two dimensional spatial phase pattern are produced on the ground. From this a power spectrum of structure sizes comprising the diffracting mechanism was determined using digital techniques. Fresnel oscillations were observed and analyzed along with some comments on the statistical stationarity of the shape of the power spectrum observed.
Three schemes for pseudocoherent demodulation of differential-phase-shift keyed (DPSK) radio signals proposed for use in land-mobile/satellite communications. Enables fast reacquisition. Also amounts to compromise between two extremes of coherent demodulation and differentially coherent demodulation, for which bit-error rates greater than those of coherent demodulation by amounts corresponding to difference of about 1 dB in bit-energy/noise-energy ratio. Based on maximum-likelihood estimation and detection during N-symbol observation periods, where N integer typically chosen between 5 and 15.
Polarization effect on radio signals scattered by meteor trails
The geometries of dense solar wind clouds are estimated by comparing single-location measurements of the solar wind plasma with the average of the electron density obtained by radio signal delay measurements along a radio path between earth and interplanetary spacecraft. Several of these geometries agree with the current theoretical spatial models of flare-induced shock waves. A new class of spatially limited structures that contain regions with densities greater than any observed in the broad clouds is identified. The extent of a cloud was found to be approximately inversely proportional to its density.