We compare water vapor measurements from the Naval Research Laboratory ground‐based Water Vapor Millimeter‐wave Spectrometer (WVMS) instruments with measurements taken by five space‐based instruments. For coincident measurements the retrievals from all of the instruments show qualitatively similar altitude profiles. The retrieved mixing ratios from most instruments generally differ from an average calculated using retrievals from all of the instruments by <1 ppmv at most altitudes from 40 km to 80 km. Comparisons with the Microwave Limb Sounder (MLS) and the Halogen Occultation Experiment (HALOE) allow for the validation of observed temporal variations. The observed variations show similar annual and semiannual cycles. A comparison of several years of data from HALOE and WVMS also shows that the instruments are detecting similar interannual variations. A regression analysis of the WVMS and HALOE data sets shows that the observed variability is consistent within the estimated errors in the mesosphere and that in the upper stratosphere, where the natural variability is small, there is a positive correlation between the WVMS and the HALOE data.

The Millimeter-Wave Atmospheric Sounder (MAS) is a shuttle-based limb-sounding instrument designed for global spectroscopic studies of O-3, and constituents important in O-3 photochemistry, in the middle atmosphere. It is part of the NASA's Atmospheric Laboratory for Applications and Science (ATLAS) spacelab shuttle mission. This paper presents an overview of the instrument, operation, and data analysis. In addition, as an example of the results, we present zonal average retrievals for O-3, H2O, and ClO obtained in ATLAS 1. The MAS O-3 and H2O measurements are shown to agree well with simultaneous observations made with the UARS MLS instrument.

We present data obtained during more than 3 years of nearly continuous measurements of middle atmospheric water vapor. The data are obtained from ground‐based measurements at 22 GHz taken at two sites, one in each hemisphere, using the Naval Research Laboratory water vapor millimeter‐wave spectrometer (WVMS). With the construction of a second instrument, it has been possible to maintain continuous monitoring from both sites since January 1994. The measurements from both instruments show significant seasonal variability. There is a clear annual cycle, with the water vapor above ∼60 km increasing in summer and decreasing in winter. The observed amplitude of the annual oscillation is larger at 45.0°S than at 34.4°N, a result which is qualitatively consistent with the higher latitude of the southern hemisphere site. There is also an indication of a semiannual cycle, particularly at altitudes near 80 km. The annual cycle is consistent with transport due primarily to advection, while the weaker semiannual cycle may be indicative of the effect of gravity waves on diffusive transport.

We present measurements of the middle atmospheric water vapor mixing ratio profile obtained using the ground‐based Naval Research Laboratory water vapor millimeter‐wave spectrometer (WVMS) instrument at the Jet Propulsion Laboratory Table Mountain Observatory. The measurements cover a period of 262 days from January 23, 1992, to October 13, 1992. During this campaign it was possible to retrieve useful daily mixing ratio profiles for 186 days. We thus have a nearly continuous record of water vapor mixing ratios for altitudes from ≈35 to 75 km. The retrievals are obtained using the optimal estimation method. Details of the error analysis are presented, and a technique is introduced that reduces baseline effects and helps to estimate the baseline error. The high‐altitude (≳65 km) data show a sharp rise prior to the expected maximum near the summer solstice and a gradual decline in the following months. The mixing ratios generally peak between 55 and 65 km, at which point the mixing ratios are 6–7 parts per million by volume. The highest peaks occur in January, May, and October.

The results of observations of Jupiter's synchrotron radiation during the period surrounding the impacts of comet Shoemaker‐Levy/9 are reported. The observations were made at the Naval Research Laboratory's Maryland Point Observatory 85 foot radio antenna operating at 1665 MHz (18 cm). The data indicate that an increase in the intensity of the synchrotron emission of 23% took place over the full duration of the impact period. The increase was accompanied by two characteristic changes in the beaming curve: a flattening and the creation of brightness temperature variations on hourly timescales. We interpret the latter as longitudinal variations in the beaming curve which suggests a localized mechanism resulting in a redistribution of the radiating electrons in the Jovian radiation belts.

We report on new developments of the WVMS instrument that provide extended altitude coverage (25-75 km) and precision that have not been achieved before with ground based microwave remote sensing of water vapor. This paper emphasizes the technical details of the instrument, experimental techniques, and especially accuracy and calibration issues.

The water vapor monitoring system (WVMS) is a ground based broad band microwave (22.235 GHz) radiometer that analyzes emission spectra from the mesosphere to determine water vapor mixing ratios. This paper emphasizes the technical details of the instrument, experimental techniques, comparison of alternate techniques, and especially accuracy and calibration issues.<>

The Millimeter Wave Atmospheric Sounder (MAS) will be launched in the spring of 1992 as part of the ATLAS 1 (Atmospheric Laboratory for Application and Science) mission. Using passive limb-scanning millimeter-wave radiometry, it will sense the thermal emission produced by ozone at 184 GHz, water vapor at 183 GHz, chlorine monoxide at 204 GHz, and oxygen (for retrieval of temperature and pressure) at 60 GHz. From these observations, concentration profiles of these gases throughout the middle atmosphere will be made. The fundamentals of the measurements, the design of the radiometers, and the approaches used for the data analysis are described

view Abstract Citations (13) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Size of the Z = 0.437 H i Absorption Region toward the QSO 3C 196 Brown, R. L. ; Broderick, J. J. ; Johnston, K. J. ; Benson, J. M. ; Mitchell, K. J. ; Waltman, E. B. Abstract VLBI spectral line observations made at the frequency of the z = 0.437 H I absorption line toward the extended radio QSO 3C 196 demonstrate that the absorption does not occur against the more compact continuum structure in this object. Apparently the H I absorption line results from absorption of the lower brightness continuum emission by an intervening cloud with an angular diameter which must be greater than 0.63". For a standard cosmology (q_0_ = 0, H_0_ = 100 km s^-1^ Mpc^-1^), this corresponds to a linear extent greater than 2.25 kpc. For a spherical cloud, the mass of absorbing gas is near 7 x 10^7^ M_sun_. Thus this particular QSO absorbing cloud is surprisingly large and massive. Publication: The Astrophysical Journal Pub Date: June 1988 DOI: 10.1086/166364 Bibcode: 1988ApJ...329..138B Keywords: H I Regions; Intergalactic Media; Quasars; Very Long Base Interferometry; Absorption Spectra; Line Spectra; Molecular Clouds; Astrophysics; GALAXIES: INTERGALACTIC MEDIUM; QUASARS; RADIO SOURCES: 21 CM RADIATION full text sources ADS | data products SIMBAD (2) NED (2)

A method is derived for optimum estimation of doppler, doppler time derivative, and other parameters for doppler-type radar returns, using linear least-squares estimation procedures. It is used on radar returns from the Naval Space Surveillance System to obtain improvement of at least one order of magnitude in doppler measurement from previous practice; doppler derivative has been measured for the...

Observations were made of the radio noise background in the frequency range 150–180 kHz to provide reference data for the design of the ground wave emergency network system. These observations were undertaken at Nanjemoy, Maryland, during early summer 1983 and included 41 days of data recording. The noise environment was found to be dominated by impulsive thunderstorm noise. A typical nighttime mean noise power spectral density was 1×10−15 W m−2 Hz−1 (noise factor of 107 dB above kT0), while a typical daytime level was at least 14 dB quieter. However, the daytime level was at times significantly higher, especially during the presence of a local thunderstorm front. During local thunderstorm activity, impulses with peak power spectral density of 1×10−14 W m−2 Hz−1 were observed frequently, while the most energetic pulse detected during our monitoring period had a peak power spectral density of 6.8×10−14 W m−2 Hz−1 (Fa = 125 dB). Sample amplitude probability distributions and time probability distributions are presented for day/quiet, night, and thunderstorm conditions. Agreement with the mean noise level predictions of CCIR report 322 is satisfactory within the accuracy limits of the CCIR data.

It is well known that Very Long Baseline Interferometry (VLBI) is capable of precise time synchronization at subnanosecond levels. This paper deals with a demonstration of clock synchronization using the MKIII VBLI system. The results are compared with clock synchronization by traveling cesium clocks and GPS. The comparison agrees within the errors of the portable clocks (+ 5 ns) and GPS(+ or - 30 ns) systems. The MKIII technology appears to be capable of clock synchronization at subnanosecond levels and appears to be very good benchmark system against which future time synchronization systems can be evaluated.

: Observations were made of the radio noise background in the frequency range 150-180 kHz to provide reference data for the design of the Ground Wave Emergency Network (GWEN) system. These observations were undertaken at Nanjemoy, Maryland, during early summer 1983, and included forty-one days of data recording. The noise environment was found to be dominated by impulsive thunderstorm noise. Preliminary data analysis is presented; the recorded data is available on magnetic tape for authorized users to use for system design purposes.

A high‐precision, phase coherent link between remote interferometer stations has been developed and has been utilized in a transcontinental radio interferometer to assess the feasibility of improved astrometric and geodetic measurements. A dual‐tone transmission method effectively cancels most phase‐degrading effects. An experimental Allen variance curve indicates that stability of 1 × 10−13 was achieved over a 1‐hour period; the slope of the Allen variance curve was close to − 1 for all time intervals up to 24 hours, indicating that the link is truly phase stable at frequencies of less than 1 GHz. Changes in the link path were measured with an accuracy of 300 ps, corresponding to 10 cm, over periods of several hours.