Data Set Information
DATA_SET_NAME MAGELLAN V RSS 5 OCCULTATION PROFILE REF TEMP PRES DENS V1.0
DATA_SET_ID MGN-V-RSS-5-OCC-PROF-RTPD-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set includes vertical profiles of refractivity, temperature, pressure and density in the neutral Venus atmosphere. The data set is composed of the following parameter fields (listed as the field name followed by a description). Parameters : WAVELENGTH - radio carrier wavelength (X-band or S-band). ORBIT_NUMBER - orbit number (3212, 3213, or 3214). ERT - Earth received time of the observation (UT). ALTITUDE - altitude above 6052 km, km. (Note that this reference surface is one km higher than the 6051 km Venus radius adopted by the MGN project). REFRACTIVITY - refractivity, N-units [(index of refraction -1) * 10**6]. REFRACT_DEV - refractivity standard deviation, N-units [(index of refraction -1) * 10**6]. TEMPERATURE - temperature, K. TEMP_DEV - temperature standard deviation, K. PRESSURE - pressure, bar. PRESS_DEV - pressure standard deviation, bar. DENSITY - density, kg/m**3. DENS_DEV - density standard deviation, kg/m**3. LATITUDE - latitude at the proximate point (the deepest level of the atmosphere probed by the radio beam), deg (North is positive). See [DAVIESETAL1992] for a discussion of the Venus cartographic coordinate system. LONGITUDE - east longitude (Venus body-fixed) at the proximate point (the deepest level of the atmosphere probed by the radio beam), deg. See [DAVIESETAL1992] for a discussion of the Venus cartographic coordinate system. ZENITH_ANGLE - solar zenith angle at the proximate point (the deepest level of the atmosphere probed by the radio beam), deg. LOCAL_TIME - local time at the proximate point (the deepest level of the atmosphere probed by the radio beam), hours (1/24 local day). Data were obtained from dual-frequency ingress radio occultation experiments using the Magellan orbiter on three consecutive orbits (#3212 - #3214) on October 5 and 6, 1991. The radio signals probed a region of the atmosphere near 65 degrees N latitude, reaching as low as 35 km altitude at X-band (3.6 cm wavelength or 8.426 GHz frequency) and below 34 km altitude at S-band (13 cm wavelength or 2.298 GHz frequency) above a mean planetary radius of 6052 km. (Note that this reference surface is one km higher than the 6051 km Venus radius adopted by the MGN project). A full description of the spacecraft performance and the design of the experiment is discussed in [STEFFESETAL1994]. Data processing and results are discussed in [JENKINSETAL1994]. Processing : The raw data sets consisted of open-loop recordings of the 13-cm and 3.6-cm carrier signals received at DSN Station 43 at Tidbinbilla (near Canberra), Australia, along with spacecraft trajectory and planetary ephemerides information, supplied by JPL Navigation and the Magellan Project, and reconstructions of the actual limb-tracking maneuvers executed by the spacecraft, supplied by Martin Marietta Corporation. The open-loop recordings contained four channels digitized at 8-bits and sampled at 50 kHz: right hand and left hand circular polarization (RCP and LCP) at 13 cm and 3.6 cm. The receiver bandwidths were 20 kHz prior to sampling. Since Magellan transmits in linear polarization at 13 cm, the 13-cm RCP and LCP signals each contained half the power received at the ground station, but were not in phase with one another. At 3.6 cm, Magellan transmits in RCP, so that the 3.6-cm signal of primary interest was the RCP channel. Obtaining atmospheric profiles from the raw data sets required several steps. Most of these are routine and well-documented in the literature (e.g. [FJELDBO&ESHLEMAN1968]; [LIPA&TYLER1979]; [JENKINS&STEFFES1991]; and [JENKINS1992]). First, the open loop recordings were processed to obtain time-series of frequency and power (log intensity) for each channel. The frequency time-series were used to determine the 13-cm and 3.6-cm refractivity profiles, from which the temperature, pressure and density profiles were derived. These steps are described in more detail in [JENKINSETAL1994].
DATA_SET_RELEASE_DATE 1996-06-27T00:00:00.000Z
START_TIME 1991-10-05T12:00:00.000Z
STOP_TIME 1991-10-06T12:00:00.000Z
MISSION_NAME MAGELLAN
MISSION_START_DATE 1989-05-04T12:00:00.000Z
MISSION_STOP_DATE 1994-10-12T12:00:00.000Z
TARGET_NAME VENUS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MGN
INSTRUMENT_NAME RADIO SCIENCE SUBSYSTEM
INSTRUMENT_ID RSS
INSTRUMENT_TYPE RADIO SCIENCE
NODE_NAME Planetary Atmospheres
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Data Coverage and Quality : These experiments probed the neutral atmosphere at altitudes between 33 and 100 km. The experiment geometry was nearly identical for all three occultations. The angle between the spacecraft orbit plane and the direction to Earth at the time of the measurements was about 28 degrees, so that the occultations were nondiametric. Hence the ray paths sliced obliquely through the atmosphere. In traversing the range of altitudes given above, the proximate point (point of closest approach to Venus along the ray path) sampled latitudes from 68 to 56 degrees N, longitudes from 128 to 139 degrees E, and solar zenith angles from 109 to 114 degrees. See DAVIESETAL1992 for a discussion of the Venus cartographic coordinate system. The direction along the ray path near the proximate point nearly coincided with the local east-west direction on Venus (it varied between 280 and 290 degrees from North during each experiment). As the atmosphere of Venus rotates about 10 degrees during each 3.25 hour orbit of the spacecraft, these data made it possible to investigate short-term variations and to place constraints on the zonal variability in the Venus atmosphere. These signals probe deeper than any previous radio occultation profiles of Venus, and with lower uncertainties. Error bars were placed on all derived parameters using the standard propagation of errors. Numerical simulations with analytical models for the Venus atmosphere were conducted to validate the processing and to confirm the magnitude of the error bars placed on the profiles. PDS Peer Review : The peer review of these data began in December 1994 and was concluded on January 17, 1995. The data and accompanying documentation were accepted for archival and distribution by the PDS. The peer-review committee included: Jon Jenkins Ron Joyner Marc Kolodner Steve Lee Dick Simpson Paul Steffes
CITATION_DESCRIPTION Citation TBD
ABSTRACT_TEXT This data set includes vertical profiles of refractivity, temperature, pressure and density in the neutral Venus atmosphere. The data set is composed of the following parameter fields (listed as the field name followed by a description).
PRODUCER_FULL_NAME JON JENKINS
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