Data Set Information
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| DATA_SET_NAME |
VG1/VG2 JUPITER IRIS DERIVED GREAT RED SPOT PARAMETERS V1.0
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| DATA_SET_ID |
VG1/VG2-J-IRIS-5-GRS-ATMOS-PARAMS-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : The data set contains Jovian atmospheric parameters derived from spectra obtained with the Voyager infrared interferometer spectrometer (IRIS). The data set is ordered by time as measured by the Flight Data System Count (FDSC). This represents the data frame number; the last two digits are modulo 60. Also included in the data set are information on pointing and associated geometry of the measurements and brightness temperatures obtained from measured radiances at selected wavenumbers. Parameters : The primary emphasis of this data set is on parameters derived from spectral measurements of Jupiter's Great Red Spot (GRS) and surrounding regions. The results included in the records between FDSC 1636631 and 1636729 are from a sequence known as the 'GRS Cross' acquired from Voyager 1. This consists of north-south and east-west scans through the GRS. In most cases, two measurements were made at each pointing location. The diameter of the IRIS field of view on the planet corresponds to about one-fifth of the east-west dimension of the spot. Data records with FDSCs between 2062839 and 2063011 contain derived parameters for a Voyager 2 GRS mosaic at somewhat higher resolution. The remaining records in the data set are from miscellaneous Voyager 1 observational sequences. The derived atmospheric parameters include retrieved atmospheric temperatures at the 143 mbar and 267 mbar levels, the fraction of the molecular hydrogen in the para state in a layer nominally centered near 300 mbar, cloud optical depths at 226 cm**-1 and 2050 cm**-1, and the ammonia mole fraction at 600 mbar relative to the equivalent solar value (0.000178). The methods used for retrieving the para hydrogen fraction and atmospheric temperatures are discussed in [CONRATH&GIERASCH1984], while the retrieval algorithms used to obtain the cloud optical depths and the ammonia abundance are described in [CONRATH&GIERASCH1986]. To obtain the para hydrogen fraction and the atmospheric temperature in the upper troposphere, measurements were used in the S(0) and S(1) collision-induced spectral lines of molecular hydrogen, which result from transitions between para and ortho states, respectively. If a measurement in the S(1) line is combined with a measurement in the S(0) line at a similar nominal optical depth, then because of the differing sensitivity to the ortho-para hydrogen ratio, it is possible to estimate both an atmospheric temperature and a para hydrogen fraction. This principle forms the basis of the algorithm used for the rapid estimation of para hydrogen and temperature from the measured spectra. Measurements near 520 and 600 cm**-1 in the S(1) line were first used to retrieve temperature in the upper troposphere, taking into account the emission angle appropriate to the measurements. The resulting atmospheric temperatures were then used to calculate theoretical brightness temperatures at 330 cm**-1 in the S(0) line for comparison with measured values to determine the para hydrogen fraction. In the interest of computational speed, the synthetic brightness temperatures were calculated for only two values of the para hydrogen fraction, and the final para hydrogen fraction estimate is obtained from the measured brightness temperature by linear interpolation. This retrieval pertains to an atmospheric layer that is nominally centered near 300 mbar and moves upward with increasing emission angle. Processing : The algorithms used for the retrieval of the cloud optical depths and the ammonia abundance are discussed in [CONRATH&GIERASCH1986]. The cloud optical depth near 5 micrometers is based on brightness temperature measurements in a spectral band 100 cm**-1 wide centered at 2050 cm**-1. In this spectral region it was found that scattering must be taken into account in the analysis. This was accomplished using a 2-stream radiative transfer approximation. The required value of the single scattering albedo was inferred to be approximately 0.75, based on IRIS measurements of spectral radiance as a function of emission angle. Next, the ammonia abundance was inferred from a measurement in an ammonia absorption line at 216 cm**-1. Finally, the cloud optical depth near 50 micrometers was inferred from a measurement at 225 cm**-1 in the continuum between ammonia lines. The residual ammonia gas absorption was taken into account, using the previously inferred ammonia abundance. In these retrievals, a single cloud layer was invoked with a base pressure of 680 mbar and a scale height equal to 0.14 times the gas scale height. The ammonia vertical distribution was modeled with a scale height equal to that of the cloud above 680 mbar and with a mole fraction independent of height at deeper levels. Results from these retrievals have been presented in [SADAETAL1996]. Ancillary Data : In addition to the retrieved atmospheric parameters, integrated measurements from the broad band visible radiometer are included, along with brightness temperatures associated with the radiances used in the retrievals. The emission angle and the solar zenith angle for the central point of the field of view projected onto the planet are provided along with the slant distance (in km) from the spacecraft to the central point. The latitude and longitude of the central point are given as are the coordinates of eight additional points equally spaced around the periphery of the field of view.
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| DATA_SET_RELEASE_DATE |
1995-08-01T00:00:00.000Z
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| START_TIME |
1979-01-01T12:00:00.000Z
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| STOP_TIME |
1981-12-31T12:00:00.000Z
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| MISSION_NAME |
COMET SL9/JUPITER COLLISION
VOYAGER
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| MISSION_START_DATE |
1993-01-01T12:00:00.000Z
1972-07-01T12:00:00.000Z
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| MISSION_STOP_DATE |
1996-01-01T12:00:00.000Z
N/A (ongoing)
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| TARGET_NAME |
JUPITER
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
VG1
VG2
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| INSTRUMENT_NAME |
INFRARED INTERFEROMETER SPECTROMETER AND RADIOMETER
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| INSTRUMENT_ID |
IRIS
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| INSTRUMENT_TYPE |
INFRARED SPECTROMETER
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| NODE_NAME |
Planetary Atmospheres
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview : In evaluating the confidence level of a given data record, several factors should be taken into account. These include the propagation of measurement noise, the uncertainties introduced by modeling assumptions that are incorporated in the algorithms, and pointing uncertainties. An estimate of the error in the para hydrogen fraction from an individual measurement due to instrument noise propagation only is + or - 0.005 at low latitudes, increasing to + or - 0.010 at high latitudes. The formal error in the retrieved temperatures due to noise propagation is approximately + or - 0.5 kelvin, while the fractional error in the optical depths and the ammonia abundance is estimated at + or - 10%. The systematic errors due to modeling assumptions cannot be easily estimated. The user should become thoroughly familiar with these assumptions, as they may pertain to his or her particular application, by referring to [CONRATH&GIERASCH1984] and [CONRATH&GIERASCH1986]. The pointing information for each record is used both to locate the data on the planet and to calculate the emission angle required in the retrievals. The quoted 3-sigma uncertainty in the pointing data taken from the Supplementary Experimenter Data Records (SEDR) is 0.15 degrees (compared with the 0.25 degree diameter IRIS field of view). (A SEDR consists of a tape of spacecraft and instrument-specific geometric information supplied by the Voyager project.) In addition, there are sometimes systematic errors in the SEDR pointing values for entire data sequences or links that take the form of approximately constant offsets in the given field of view locations on the planet. Data Coverage and Quality : It is believed that the pointing for the records included here is reasonably accurate. The SEDRs used in the construction of this data set were generated in 1991, and C-smithing was employed. It should be noted that earlier versions of SEDRs were used for obtaining the pointing information that is included with the IRIS spectral data sets. As a consequence, the pointing given in the present data set may not be in exact agreement with that included with the spectral data sets. When attempting to correlate IRIS data with those from other Voyager instruments, it may be necessary to take into account the relative offsets of the centers of the fields of view of the various instruments. Offsets relative to the center of the ISS Narrow Angle camera field of view are given in the tables below. Elevation is positive to the right within the imaging field of view and cross elevation is positive downward. The offsets are expressed both in degrees and in Narrow Angle pixels. Voyager 1: Instrument Elevation Cross-Elevation IRIS +0.020 deg +0.024 deg (+37.7 pixels) (+45.3 pixels) ISS(WA) +0.0315 deg +0.0247 deg (+59.4 pixels) (+46.6 pixels) UVS +0.010 deg -0.030 deg (+18.9 pixels) (-56.6 pixels) Voyager 2: Instrument Elevation Cross-Elevation IRIS +0.016 deg -0.009 deg (+30.2 pixels) (-17.0 pixels) ISS(WA) -0.0308 deg -0.0068 deg (-58.1 pixels) (-12.8 pixels) UVS 0.0 deg +0.08 deg (0.0 pixels)(+150.9 pixels) PPS -0.06 deg +0.003 deg (-113.2 pixels) (+5.7 pixels)
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| CITATION_DESCRIPTION |
Citation TBD
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| ABSTRACT_TEXT |
The data set contains Jovian atmospheric parameters derived from spectra obtained with the Voyager infrared interferometer spectrometer (IRIS). The data set is ordered by time as measured by the Flight Data System Count (FDSC). This represents the data frame number modulo 60. Also included in the data set are information on pointing and associated geometry of the measurements and brightness temperatures obtained from measured radiances at selected wavenumbers.
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| PRODUCER_FULL_NAME |
BARNEY J. CONRATH
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| SEARCH/ACCESS DATA |
Atmospheres Online Archives
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