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M. A. Janssen J. E. Oswald S. T. Brown S. Gulkis S. M. Levin S. J. Bolton M. D. Allison S. K. Atreya D. Gautier A. P. Ingersoll J. I. Lunine G. S. Orton T. C. Owen P. G. Steffes V. Adumitroaie A. Bellotti L. A. Jewell C. Li L. Li S. Misra F. A. Oyafuso D. Santos-Costa E. Sarkissian R. Williamson J. K. Arballo A. Kitiyakara A. Ulloa-Severino J. C. Chen F. W. Maiwald A. S. Sahakian P. J. Pingree K. A. Lee A. S. Mazer R. Redick R. E. Hodges R. C. Hughes G. Bedrosian D. E. Dawson W. A. Hatch D. S. Russell N. F. Chamberlain M. S. Zawadski B. Khayatian B. R. Franklin H. A. Conley J. G. Kempenaar M. S. Loo E. T. Sunada V. Vorperion C. C. Wang 《Space Science Reviews》2017,213(1-4):139-185
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A unique kinetic isotope effect has been found in the formation process of ozone molecules. Isotope enrichments of about 10%
above statistically expected values were first discovered in atmospheric isotopomers 49O3 and 50O3 and later in many other molecular combinations. Most recently the source of this effect was identified through measurement
of isotope-specific ozone formation rate coefficients which show a large variability of over 50%. Ozone molecule formation
is a complex process since different reaction channels contribute to a specific isotopomer. In addition, fast oxygen isotope
exchange reactions determine the abundance of atomic oxygen participating in ozone formation. The isotope enrichments observed
are both pressure and temperature-dependent and they decrease at pressures above 100 mbar and toward lower temperatures. Ozone
possesses not only one of the most unusual isotope anomalies, it also serves as a mediator by transferring heavy oxygen from
the O2 reservoir to other species. Stratospheric isotope composition of CO2 has been recently measured with high accuracy and a pronounced isotopic signature was found which shows that 17O is preferentially transferred from O3 into CO2.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Radar: The Cassini Titan Radar Mapper 总被引:1,自引:0,他引:1
C. Elachi M. D. Allison L. Borgarelli P. Encrenaz E. Im M. A. Janssen W. T. K. Johnson R. L. Kirk R. D. Lorenz J. I. Lunine D. O. Muhleman S. J. Ostro G. Picardi F. Posa C. G. Rapley L. E. Roth R. Seu L. A. Soderblom S. Vetrella S. D. Wall C. A. Wood H. A. Zebker 《Space Science Reviews》2004,115(1-4):71-110
The Cassini RADAR instrument is a multimode 13.8 GHz multiple-beam sensor that can operate as a synthetic-aperture radar (SAR) imager, altimeter, scatterometer, and radiometer. The principal objective of the RADAR is to map the surface of Titan. This will be done in the imaging, scatterometer, and radiometer modes. The RADAR altimeter data will provide information on relative elevations in selected areas. Surfaces of the Saturn’s icy satellites will be explored utilizing the RADAR radiometer and scatterometer modes. Saturn’s atmosphere and rings will be probed in the radiometer mode only. The instrument is a joint development by JPL/NASA and ASI. The RADAR design features significant autonomy and data compression capabilities. It is expected that the instrument will detect surfaces with backscatter coefficient as low as −40 dB.RADAR Team LeaderThis revised version was published online in July 2005 with a corrected cover date. 相似文献
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MIRO: Microwave Instrument for Rosetta Orbiter 总被引:1,自引:0,他引:1
S. Gulkis M. Frerking J. Crovisier G. Beaudin P. Hartogh P. Encrenaz T. Koch C. Kahn Y. Salinas R. Nowicki R. Irigoyen M. Janssen P. Stek M. Hofstadter M. Allen C. Backus L. Kamp C. Jarchow E. Steinmetz A. Deschamps J. Krieg M. Gheudin D. Bockelée-Morvan N. Biver T. Encrenaz D. Despois W. Ip E. Lellouch I. Mann D. Muhleman H. Rauer P. Schloerb T. Spilker 《Space Science Reviews》2007,128(1-4):561-597
The European Space Agency Rosetta Spacecraft, launched on March 2, 2004 toward Comet 67P/Churyumov-Gerasimenko, carries a
relatively small and lightweight millimeter-submillimeter spectrometer instrument, the first of its kind launched into deep
space. The instrument will be used to study the evolution of outgassing water and other molecules from the target comet as
a function of heliocentric distance. During flybys of the asteroids (2867) Steins and (21) Lutetia in 2008 and 2010 respectively,
the instrument will measure thermal emission and search for water vapor in the vicinity of these asteroids.
The instrument, named MIRO (Microwave Instrument for the Rosetta Orbiter), consists of a 30-cm diameter, offset parabolic
reflector telescope followed by two heterodyne receivers. Center-band operating frequencies of the receivers are near 190
GHz (1.6 mm) and 562 GHz (0.5 mm). Broadband continuum channels are implemented in both frequency bands for the measurement
of near surface temperatures and temperature gradients in Comet 67P/Churyumov-Gerasimenko and the asteroids (2867) Steins
and (21) Lutetia. A 4096 channel CTS (Chirp Transform Spectrometer) spectrometer having 180 MHz total bandwidth and 44 kHz
resolution is, in addition to the continuum channel, connected to the submillimeter receiver. The submillimeter radiometer/spectrometer
is fixed tuned to measure four volatile species – CO, CH3OH, NH3 and three, oxygen-related isotopologues of water, H2
16O, H2
17O and H2
18O. The basic quantities measured with the MIRO instrument are surface temperature, gas production rates and relative abundances,
and velocity and excitation temperature of each species, along with their spatial and temporal variability. This paper provides
a short discussion of the scientific objectives of the investigation, and a detailed discussion of the MIRO instrument system. 相似文献
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Paul G. Steffes Thomas R. Hanley Bryan M. Karpowicz Kiruthika Devaraj Sahand Noorizadeh Danny Duong Garrett Chinsomboon Amadeo Bellotti Michael A. Janssen Scott J. Bolton 《Space Science Reviews》2017,213(1-4):187-204
The NASA Juno mission includes a six-channel microwave radiometer system (MWR) operating in the 1.3–50 cm wavelength range in order to retrieve abundances of ammonia and water vapor from the microwave signature of Jupiter (see Janssen et al. 2016). In order to plan observations and accurately interpret data from such observations, over 6000 laboratory measurements of the microwave absorption properties of gaseous ammonia, water vapor, and aqueous ammonia solution have been conducted under simulated Jovian conditions using new laboratory systems capable of high-precision measurement under the extreme conditions of the deep atmosphere of Jupiter (up to 100 bars pressure and 505 K temperature). This is one of the most extensive laboratory measurement campaigns ever conducted in support of a microwave remote sensing instrument. New, more precise models for the microwave absorption from these constituents have and are being developed from these measurements. Application of these absorption properties to radiative transfer models for the six wavelengths involved will provide a valuable planning tool for observations, and will also make possible accurate retrievals of the abundance of these constituents during and after observations are conducted. 相似文献
6.
Janssen L.H. Van Der Spek G.A. 《IEEE transactions on aerospace and electronic systems》1985,(2):208-219
From October 1982 through May 1983 an extensive weather clutter registration program was executed near the Dutch coast. Coherent echo series of 2 s were obtained from a cluster of adjacent antenna pencil beams every 10 or 15 min., mainly between 16:00 and 08:30 h and on the weekends. The beam cluster was pointed toward the intensity maximum of the clutter volume. The radar operated at 5650 MHz. Spectra with 10 Hz Doppler resolution have been computed by averaging over 19 discrete Fourier transforms of overlapping and tapered subseries of 200 echo vectors. To quantify the deviation from a Gaussian shape a spectral variability is defined which is computed for every estimated spectrum. It is found that the deviation from Gaussian is considerable in about one-fourth of the spectra. A selection of "typical worst case" spectra is presented. 相似文献
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