Phase noise instrumentation final report
Bistable multivibrator and phase locked loop for frequency division - radio frequency console instrumentation
PHASE LOCK↗
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The nighttime ionosphere of Mars from Mars-4 and Mars-5 radio occultation dual-frequency measurements
Dual frequency radio sounding of the Martian nighttime ionosphere was carried out during the exits from behind the planet of the Mars-4 spacecraft on February 2, 1974 and the Mars-5 spacecraft on February 18, 1974. In these experiments, the spacecraft transmitter emitted two coherent monochromatic signals in decimeter and centimeter wavelength ranges. At the Earth receiving station, the reduced phase difference (or frequencies) of these signals was measured. The nighttime ionosphere of Mars measured in both cases had a peak electron density of approximately 5 X 1,000/cu cm at an altitude of 110 to 130 km. At the times of spacecraft exit, the solar zenith angles at the point of occultation were 127 deg and 106 deg, respectively. The height profiles of electron concentration were obtained assuming spherical symmetry of the Martian ionosphere.
Savich, N. A.↗
Equipment for RF carrier acquisition using the MSFN S-band receiver/exciter
Equipment for radio frequency carrier acquisition using manned space flight network S-band receiver/exciter
RECEIVER↗
Observing Solar Radio Bursts from the Lunar Surface
Locating low frequency radio observatories on the lunar surface has a number of advantages. Here, we describe the Radio Observatory for Lunar Sortie Science (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff of the solar radio emissions and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLES include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 MHz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg, equivalent to a linear array size of approximately 500 meters. Operations would consist of data acquisition during the lunar day, with regular data downlinks. The major components of the ROLSS array are 3 antenna arms arranged in a Y shape, with a central electronics package (CEP). Each antenna arm is a linear strip of polyimide film (e.g., Kapton (TM)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP.
MacDowall, R. J.↗
Preliminary assessment of RFI impacts on TDRSS in the 2- to 2.3 GHz band
A study was conducted of the radio frequency bands and radio frequency interference (RFI) impacts on the TDR satellite. Quick look evaluations were performed on RFI conditions in the 136 to 138 MHz and 400.5 to 401.5 MHz bands. An approximate chronological account of the investigations and the intermediate findings are presented. The preliminary results of RFI evaluations in the nominally 2 to 2.3 GHz band. An analysis of the time interaction of user satellites with microwave radio-relay type communications beams as a source of RFI is included.
Lyttle, J. D.↗
High Angular Resolution Imaging of Solar Radio Bursts from the Lunar Surface
Locating low frequency radio observatories on the lunar surface has a number of advantages, including positional stability and a very low ionospheric radio cutoff. Here, we describe the Radio Observatory on the lunar Surface for Solar studies (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The preferred site is on the lunar near side to simplify the data downlink to Earth. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by measuring the low radio frequency cutoff of the solar radio emissions or background galactic radio emission, measuring the flux, particle mass, and arrival direction of interplanetary and interstellar dust, and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLSS include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 M Hz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg at 10 MHz, equivalent to a linear array size of approximately one kilometer. The major components of the ROLSS array are 3 antenna arms, each of 500 m length, arranged in a Y formation, with a central electronics package (CEP) at their intersection. Each antenna arm is a linear strip of polyimide film (e.g., Kapton(TradeMark)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP. Operations would consist of data acquisition during the lunar day, with data downlinks to Earth one or more times every 24 hours.
MacDowall, Robert J.↗
Long-period dynamic spectrograms of low-frequency interplanetary radio emissions
Dynamic spectrograms of the low-frequency interplanetary radio emissions as observed by Voyagers 1 and 2 from 1983 through mid-1986 are reported. The radio emissions were observed to be most intense in the latter portion of 1983 at 3 kHz but have also been detected at 2 kHz. The emission has been present almost continuously at either 2 or 3 kHz since late 1983. The spectrograms presented herein show that the phenomenon appears almost identically as observed by the two spacecraft separated by more than 10 AU, at least at the higher frequency. One feature revealed by the dynamic spectrograms which had not been noticed previously is a gradual rise in frequency of the 3-kHz component following the onset of the late 1983 event. These new observations reinforce the conclusion that the low-frequency emissions are freely propagating radio waves, but the two-component spectral structure implies that the previous model of emission at twice the plasma frequency at the inner heliosphere shock is inadequate to fully account for the observations. Either an additional source region or an additional source mechanism is suggested.
Kurth, W. S.↗
Remote sensing - Potential interference problems and solutions
The paper discusses general radio frequency interference considerations associated with frequency and bandwidth allocations for satellite-borne microwave remote sensors. The interplay of frequency allocation and radio frequency interference is discussed for the cases of passive microwave sensors and active microwave sensors, the latter case involving shared band interference and out-of-band interference.
Freibaum, J.↗
Observing Solar Radio Bursts from the Lunar Surface
Locating low frequency radio observatories on the lunar surface has a number of advantages, including fixes locations for the antennas and no terrestrial interference on the far side of the moon. Here, we describe the Radio Observatory for Lunar Sortie Science (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff of the solar radio emissions and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays designed for faint sources.
MacDowall, R. J.↗
The spectral evolution of low-frequency variable radio sources
The dynamic spectra of several low frequency extragalactic radio sources are presented. The observations were made at 318, 430, 606, 880, and 1400 MHz at several different radio observatories around the U.S. Two outbursts were observed in AO 0235 + 16 at 1.4 GHz, followed by a diminished variation at the lower frequencies. The dynamic frequencies of NRAO 140, PKS 1117 + 14, DA 406, CTA 102, and 3C 454.3 do not fit the same pattern. These radio sources displayed the following characteristics: (1) departure from straight or curved spectra at the frequencies of variation; (2) no obvious frequency drifting; and (3) negligible variation at 1.4 GHz. Possible explanations for this behavior are briefly discussed.
Dennison, B.↗
Power spectrum of small-scale density irregularities in the interstellar medium
Observations of the interstellar scintillation of radiation from 17 pulsars are reported which are used to place limits on the power spectrum of small-scale electron density irregularities in the interstellar medium. Measurements made at 340, 408, and 450 MHz in the dispersion measure range 3-57/cu cm pc of the time-dependent radio frequency spectrum of interstellar scintillations were analyzed to determine the scintillation index and a scintillation frequency-correlation scale based on the autocorrelation function in radio frequency of the fluctuations in scintillation. The dispersion-measure dependence of the scintillation frequency correlation scale is found to be consistent with both Gaussian model interstellar medium spectra and power-law spectra with indices between 3.0 and 4, while the radio-frequency scaling of the frequency correlation scale is consistent with power law indices between 2.8 and 3.9. However comparison of the shape of the radio-frequency autocorrelation function with model calculations indicates power law models with indices greater than 3.6 are possible. Data are also consistent with a local three-dimensional density spectrum at a wave number of 10 to the -9th/m of 3 x 10 to the 28th to 3 x 10 to the 29th/cu m.
Armstrong, J. W.↗
Ground-level detection of low- and medium-frequency auroral radio emissions
Natural radio emissions in the frequency range of several hundred kHz were detected at ground level in the auroral region during a ground-level observing program conducted near Fairbanks, Alaska in the spring of 1986 in an attempt to detect auroral cyclotron-maser-generated whistler modes. Most of the strongest emissions were observed in a small time interval around midnight magnetic local time, suggesting a close tie-in with auroral processes. The results support earlier reports of radio noise from the aurora at frequencies of about 100 kHz and indicate the importance of extending the upper frequency of ground-based high-latitude VLF stations to the vicinity of 1 MHz.
Benson, Robert F.↗
Rectenna for high-voltage applications
An energy transfer system is disclosed. The system includes patch elements, shielding layers, and energy rectifying circuits. The patch elements receive and couple radio frequency energy. The shielding layer includes at least one opening that allows radio frequency energy to pass through. The openings are formed and positioned to receive the radio frequency energy and to minimize any re-radiating back toward the source of energy. The energy rectifying circuit includes a circuit for rectifying the radio frequency energy into dc energy. A plurality of energy rectifying circuits is arranged in an array to provide a sum of dc energy generated by the energy rectifying circuit.
Epp, Larry W.↗
Search for microarcsecond structure in low-frequency variable radio sources
A search for interstellar scintillation (ISS) of low-frequency variable radio sources is reported. Observations of 28 confirmed or suspected low-frequency variables, 21 nonvariable sources, and two pulsars were made at 408 MHz. As expected, the pulsars showed ISS, but scintillation was not detected in any other source. A typical upper limit to the rms modulation due to ISS is 150 mJy, giving lower limits to the apparent angular diameter of about 10 to the -6th arcsec. The possibilities that a true point source is broadened to an apparent angular diameter greater than or roughly equal to 10 to the -6th arcsec by scattering local to the source or in a general intergalactic medium are discussed.
Armstrong, J. W.↗
Apollo logistics support systems molab studies. ground wave propagation on the lunar surface for a lunar mobile laboratory
Vertically polarized medium frequency radio waves for over lunar horizon communication system for lunar mobile laboratory /Molab/ mission - Apollo project
LUNAR SURFACE↗
New observations of the low frequency interplanetary radio emissions
Recent Voyager 1 observations reveal reoccurrences of the low frequency interplanetary radio emissions. Three of the new events are weak transient events which rise in frequency from the range of 2-2.5 kHz to about 3 kHz with drift rates of about 1.5 kHz/year. The first of the transient events begins in mid-1989 and the more recent pair of events was first detected in late 1990. In addition, there is an apparent onset of a 2-kHz component of the emission beginning near day 70 of 1991. The new transient emissions are barely detectable on Voyager 1 and are below the threshold of detectability on Voyager 2. The new activity provides new opportunities to test various theories of the triggering, generation, and propagation of the outer heliospheric radio emissions and may signal a response of the source of the radio emissions to the increased solar activity associated with the recent peak in the solar cycle.
Kurth, W. S.↗
New observations of the low frequency interplanetary radio emissions
Recent Voyager 1 observations reveal reoccurrences of the low frequency interplanetary radio emissions. Three of the new events are weak transient events which rise in frequency from the range of 2-2.5 kHz to about 3 kHz with drift rates of approximately 1.5 kHz/year. The first of the transient events begins in mid-1989 and the more recent pair of events both were first detected in late 1991. In addition, there is an apparent onset of a 2-kHz component of the emission beginning near day 70 of 1991. The new transient emissions are barely detectable on Voyager 1 and are below the threshold of detectability on Voyager 2, which is less sensitive than Voyager 1. The new activity provides new opportunities to test various theories of the triggering, generation, and propagation of the outer heliospheric radio emissions and may signal a response of the source of the radio emissions to the increased solar activity associated with the recent peak in the solar cycle.
Kurth, W. S.↗
RF Environment Data Analysis for UAS Operations
As the usage of radio frequency spectrum and uncrewed aircraft systems continue to grow, the radio frequency environment and its implications to flight safety should be understood. This is important to ensure control and command links as well as data collection links maintain strong communications during flight. NASA System-Wide Safety (SWS) is currently developing standards of flight safety but lacks methods for establishing confidence in the availability of radio frequency space to make a go/no-go decision for drone flights. This study examines information about the radio modules used by SWS and how they interact with the RF environment though analysis of historical spectrum data. This review studies the potential effectiveness of observing the power spread and occupancy methods as they apply to the flight system radios. It has been determined that viewing the frequency and time when the environment is greater than a threshold which indicates potential interference levels may give insight into the patterns of spectrum usage.
Radio Frequency↗