Data Set Information
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| DATA_SET_NAME |
VO1/VO2 MARS ATMOSPHERIC WATER DETECTOR 4 V1.0
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| DATA_SET_ID |
VO1/VO2-M-MAWD-4-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 : This data set consists of the raster-averaged radiant intensities and associated data parameters produced from data acquired by the Mars Atmospheric Water Detectors (MAWD) onboard the Viking Orbiters. The basic observations give temporal coverage spanning just over two martian years and variable, but extensive, spatial coverage of the planet. MAWD was a five-channel grating spectrometer measuring solar radiation reflected from the surface and atmosphere of Mars in and out of water vapor bands in the 1.4 micrometer spectral interval. The data set described here contains the solar reflected radiant intensities (i.e., radiances) measured by MAWD, derived water vapor column abundances, a derived '1.4-micrometer brightness', and ancillary data (e.g., viewing geometry, surface elevation and air mass). Column water vapor abundances were derived by comparing the reflected radiant intensities in three water vapor absorption bands to radiant intensities in the two interspersed continua; the calculation was done for the observed air mass and then normalized by the air mass to obtain a vertical column abundance. A basic description of the instrument, its observational modes and its derived data products is given in [FARMER_ETAL_1977]. A description of the global and seasonal variation of water vapor on Mars, based on the complete MAWD observational record, is given in [JAKOSKY_FARMER_1982]. This data set was generated from the raster-level data base constructed during the Viking Mission on the original data processing system (IRPS: Infrared Processing System) by the MAWD Science Team, led by C. B. Farmer, JPL. Together with the instantaneous field of view (IFOV) radiances and geometry, the raster-level radiances, associated water column abundances and ancillary data have been archived at the NSSDC (NSSDC id 75-075A-03A, 75-083A-03A). Data from the final phase of the VO-1 mission were added, supervised by R. Zurek, JPL. Eventually, the data set was restructured, additional quality flags were introduced, and a second estimate of the water vapor column abundance (WFAPT, termed COLUMN_H2O_A in the data set) was added [by R. Zurek, JPL; see [JAKOSKY_ETAL_1988].]. The data base was restructured, while preserving key unique parameters, into a consistent format with the Viking Orbiter Infrared Thermal Mapper (IRTM) data [R. Mehlman, R. Zurek]. Both the MAWD and IRTM data sets were then accessible with the XXFUNC package. Further quality checking of the MAWD data was carried out by B. Jakosky, U. Colorado. The data set contains the following fields (listed as the field name followed by a description): SC_ID Spacecraft id ORBIT_NO Orbit number SEQUENCE_NO Numeric order of a given sequence within an orbit SEQUENCE_ID Sequence identifier SEQ_TITLE Sequence title IRKS_IN_SEQ Number of irks in the sequence FDS_AT_START The count on the spacecraft internal (Flight Data System) clock at the start of the sequence IRK Raster number within the sequence (represents a 4.48 second interval). SOL_DIST_PER Solar distance at spacecraft periapsis SOL_LON_PER Areocentric solar longitude at spacecraft periapsis SOL_CLAT_PER Areocentric solar colatitude at spacecraft periapsis LATITUDE Projected latitude of the center of the raster footprint on the planet LONGITUDE Projected longitude of the center of the raster footprint on the planet SLANT_RANGE Slant distance between the spacecraft and the center of the raster footprint on the planet INCID_ANGLE Incidence angle at the center of the raster footprint on the planet EMISS_ANGLE Emission angle at the center of the raster footprint on the planet PHASE_ANGLE Phase angle at the center of the raster footprint on the planet MARTIAN_DAY Martian day, referenced to 0 degrees longitude at midnight, with day 1 beginning at Viking Orbiter 1 orbit insertion. Day is incremented by 1 when the observations cross local midnight. LOCAL_TIME Local time of day (1/24 of a martian day) at the center of the raster footprint on the planet RADIANCE_1 Radiance, channel 1 (7223.13 cm**-1) RADIANCE_2 Radiance, channel 2 (7224.50 cm**-1) RADIANCE_3 Radiance, channel 3 (7232.20 cm**-1) RADIANCE_4 Radiance, channel 4 (7238.50 cm**-1) RADIANCE_5 Radiance, channel 5 (7242.74 cm**-1) BRIGHTNESS The 1.4 micrometer brightness, range and incidence angle corrected, defined as: B:0.5 * (R2 + R4) * (DSM/1.5237)**2 / COS(I), where: B : 1.4 micrometer brightness R2 : channel 2 radiance R4 : channel 4 radiance DSM : Mars-Sun distance (AU) COS(I) : cosine of the incidence angle at the center of the raster footprint SURFACE_ELEV Surface elevation at the center of the raster footprint (derived from the 1976 USGS topographic maps) COLUMN_H2O_A The column water abundance computed using seasonally and topographically varying surface pressure and a Curtis-Godson pressure set to 1/2 the surface pressure COLUMN_H2O_B The column water abundance computed using constant effective pressure and temperature AIR_MASS The air mass through which the observation was obtained MISSING_IFOV Count of the number of instantaneous fields of view missing from the raster QUALITY The quality of geometry and calibration. For general use, constraining QUALITY <: 5 is recommended. 1 - Good data, as processed 2 - Lat/lon corrected by interpolation; surface elevation recomputed 3 - Surface elevation recomputed using database lat/lon 5 - Lat/lon updated with some uncertainty; still thought to be useful 6 - Lat/lon updated, but estimates are questionable 7 - Out-of-bounds (upper or lower) water amounts, set arbitrarily to 150.1 pm in original processing 9 to 13 - Various geometry problems: incorrect lat, lon, emission, or incidence 18 - Rasters with bad radiances or many data defects Processing Level Id : 4 Software Flag : Y Processing Start Time : 1976 Processing Stop Time : 1981 Native Start Time : 415147628 (FLIGHT DATA SYSTEM CLOCK CNT) Native Stop Time : 964563436 (FLIGHT DATA SYSTEM CLOCK CNT) Parameters : Data Set Parameter 'BRIGHTNESS TEMPERATURE' ------------------------------------------- The kinetic temperature of an ideal blackbody which, if observed with the spectral response of the instrument spectral channel in question would yield the observed radiance. Data Set Parameter Name : BRIGHTNESS TEMPERATURE Data Set Parameter Unit : KELVIN Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1.12 Sampling Parameter Interval : 1.12 Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'DERIVATIVE OF MODEL WITH ALBEDO' ---------------------------------------------------- The differential dependence of model temperature upon the assumed surface bolometric bond albedo, at the nominal value of model thermal inertia. Data Set Parameter Name : DERIVATIVE OF MODEL WITH ALBEDO Data Set Parameter Unit : DEGREES Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'DERIVATIVE OF MODEL WITH INERTIA' ----------------------------------------------------- The differential dependence of model temperature upon the assumed surface thermal inertia, at the nominal value of model bolometric bond albedo. Data Set Parameter Name : DERIVATIVE OF MODEL WITH INERTIA Data Set Parameter Unit : KELVIN / (10**(-3)*CAL*CM**(-2)*S**(-1/2)*K**(-1)) Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'LAMBERT ALBEDO' ----------------------------------- The reflectance of a grey Lambert (ideal diffuse) smooth surface parallel to the target body geoid which would yield the observed reflected radiation in the absence of any atmosphere. Data Set Parameter Name : LAMBERT ALBEDO Data Set Parameter Unit : N/A Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1.12 Sampling Parameter Interval : 1.12 Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'MINNAERT ALBEDO' ------------------------------------ Albedo computed presuming a Minnaert behavior, with the Minnaert exponent k equal to 0.95. A_m : Visual_Brightness * cos(incidence angle)**-k * cos(emission angle)**(1.-k). Data Set Parameter Name : MINNAERT ALBEDO Data Set Parameter Unit : N/A Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1.12 Sampling Parameter Interval : 1.12 Minimum Available Sampling Int : 1.12 Noise Level : N/A Data Set Parameter 'MODEL TEMPERATURE' -------------------------------------- The surface kinetic temperature calculated using a nominal set of parametric values for a smooth planet of uniform physical properties and for the latitude, time of day, and season of the observation. The model used for the Viking IRTM is described in the appendix of [KIEFFER_ETAL_1977]. Data Set Parameter Name : MODEL TEMPERATURE Data Set Parameter Unit : KELVIN Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'PHASE CORRECTED ALBEDO' ------------------------------------------- Albedo computed using a phase dependence derived from IRTM observations (See [KIEFFER_ETAL_1977]). A_g : A_l * (1.+0.000146*exp(0.075*phase_angle) where A_l : Visual_brightness / cos(incidence angle) Data Set Parameter Name : PHASE CORRECTED ALBEDO Data Set Parameter Unit : N/A Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1.12 Sampling Parameter Interval : 1.12 Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'SINGLE POINT THERMAL INERTIA' ------------------------------------------------- The thermal inertia which would yield the observed brightness temperature, based on the observed Lambert albedo, the model temperature and partial derivatives of model temperature with albedo and inertia, and an approximation of the non-linear dependence of model temperatures with respect to thermal inertia. If the observation was at night, so that no measure of albedo was made, the albedo is assumed to be the same as in the nominal thermal model. Data Set Parameter Name : SINGLE POINT THERMAL INERTIA Data Set Parameter Unit : 10**(-3)*CAL*CM**(-2)*S**(-1/2)*K**(-1) Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : N/A Sampling Parameter Interval : N/A Minimum Available Sampling Int : N/A Noise Level : N/A Data Set Parameter 'VISUAL BRIGHTNESS' -------------------------------------- The radiant energy measured in the IRTM solar band (0.3-3.0 microns), normalized to that expected for an ideal Lambert reflector observed under normal incidence at the current heliocentric range of the target body. Data Set Parameter Name : VISUAL BRIGHTNESS Data Set Parameter Unit : WATT/(METER*METER)/STERADIAN Sampling Parameter Name : TIME Sampling Parameter Unit : SECOND Minimum Sampling Parameter : N/A Maximum Sampling Parameter : N/A Sampling Parameter Resolution : 1.12 Sampling Parameter Interval : 1.12 Minimum Available Sampling Int : N/A Noise Level : N/A Source Instrument Parameters : Instrument Host ID : VO1 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 1 Important Instrument Parameters : 1 Instrument Host ID : VO2 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 1 Important Instrument Parameters : 1 Instrument Host ID : VO1 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 2 Important Instrument Parameters : 1 Instrument Host ID : VO2 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 2 Important Instrument Parameters : 1 Instrument Host ID : VO1 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 3 Important Instrument Parameters : 1 Instrument Host ID : VO2 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 3 Important Instrument Parameters : 1 Instrument Host ID : VO1 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 4 Important Instrument Parameters : 1 Instrument Host ID : VO2 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 4 Important Instrument Parameters : 1 Instrument Host ID : VO1 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 5 Important Instrument Parameters : 1 Instrument Host ID : VO2 Data Set Parameter Name : RADIANCE Instrument Parameter Name : RADIANCE CHANNEL 5 Important Instrument Parameters : 1 Instrument Host ID : VO1 Data Set Parameter Name : 1.4 MICROMETER BRIGHTNESS Instrument Parameter Name : RADIANCE CHANNEL 2 Important Instrument Parameters : 2 Instrument Host ID : VO2 Data Set Parameter Name : 1.4 MICROMETER BRIGHTNESS Instrument Parameter Name : RADIANCE CHANNEL 2 Important Instrument Parameters : 2 Instrument Host ID : VO1 Data Set Parameter Name : 1.4 MICROMETER BRIGHTNESS Instrument Parameter Name : RADIANCE CHANNEL 4 Important Instrument Parameters : 2 Instrument Host ID : VO2 Data Set Parameter Name : 1.4 MICROMETER BRIGHTNESS Instrument Parameter Name : RADIANCE CHANNEL 4 Important Instrument Parameters : 2 Instrument Host ID : VO1 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 1 Important Instrument Parameters : 5 Instrument Host ID : VO2 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 1 Important Instrument Parameters : 5 Instrument Host ID : VO1 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 2 Important Instrument Parameters : 5 Instrument Host ID : VO2 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 2 Important Instrument Parameters : 5 Instrument Host ID : VO1 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 3 Important Instrument Parameters : 5 Instrument Host ID : VO2 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 3 Important Instrument Parameters : 5 Instrument Host ID : VO1 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 4 Important Instrument Parameters : 5 Instrument Host ID : VO2 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 4 Important Instrument Parameters : 5 Instrument Host ID : VO1 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 5 Important Instrument Parameters : 5 Instrument Host ID : VO2 Data Set Parameter Name : COLUMN WATER ABUNDANCE Instrument Parameter Name : RADIANCE CHANNEL 5 Important Instrument Parameters : 5 Processing : Processing History ------------------ Source Data Set ID : IFOV LEVEL MAWD DATA Software : FAPT: H2O VAPOR PROD ALGORITHM Product Data Set ID : VO1/VO2-M-MAWD-4-V1.0 Source Data Set ID : IFOV LEVEL MAWD DATA Software : IRPS: INFRARED PROCESSING SYS Product Data Set ID : VO1/VO2-M-MAWD-4-V1.0 Software 'FAPT' --------------- Source Data Set ID : IFOV LEVEL MAWD DATA Software Name : FAPT: H2O VAPOR PROD ALGORITHM Product Data Set ID : VO1/VO2-M-MAWD-4-V1.0 Software Type : N/A Software Release Date : N/A Node ID : N/A Cognizant Engineer : N/A Software Access Description : N/A Software 'IRPS' --------------- Source Data Set ID : IFOV LEVEL MAWD DATA Software Name : IRPS: INFRARED PROCESSING SYS Product Data Set ID : VO1/VO2-M-MAWD-4-V1.0 Software Name : N/A Software Type : N/A Software Release Date : N/A Node ID : N/A Cognizant Engineer : N/A Software Access Description : N/A
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| DATA_SET_RELEASE_DATE |
1989-11-01T00:00:00.000Z
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| START_TIME |
1976-06-22T12:00:00.000Z
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| STOP_TIME |
1980-07-30T12:00:00.000Z
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| MISSION_NAME |
VIKING
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| MISSION_START_DATE |
1975-08-20T12:00:00.000Z
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| MISSION_STOP_DATE |
1983-02-01T12:00:00.000Z
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| TARGET_NAME |
MARS
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
VO1
VO2
|
| INSTRUMENT_NAME |
MARS ATMOSPHERIC WATER DETECTOR
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| INSTRUMENT_ID |
MAWD
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| INSTRUMENT_TYPE |
INFRARED SPECTROMETER
|
| NODE_NAME |
Planetary Atmospheres
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Overview : When taking data, MAWD acquired 15 successive instantaneous fields-of-view (IFOVs) every 4.48 seconds. Because of low signal-to-noise for any given IFOV, the 15 IFOV-level radiances were averaged to produce a 'raster-level' radiance associated with a roughly equi-dimensional 'footprint', which was the sum of the 15 IFOVs. Together with the IFOV radiances and geometry, the raster-level radiances, associated water column abundances and ancillary data have been archived at the NSSDC (NSSDC id 75-075A-03A, 75-083A-03A). The present data set differs from the NSSDC data in three ways: 1) Only the raster-level data, with their higher signal-to-noise values, are used; 2) more detailed quality flags have been assigned; and 3) a second calculation of the vertical column water abundance (WFAPT, termed COLUMN_H2O_A in the data set) has been added. Unlike the original calculation (WAPT, termed COLUMN_H2O_B in the data set), which assumed a constant pressure for spectral-line formation and absorption, WFAPT uses the end-of-mission water vapor software production algorithm (FAPT) and a Curtis-Godson pressure set to 1/2 the surface pressure, as computed based on the observed seasonal trend of surface pressure at Viking Lander 1 and scaled by the surface elevation of the center of the raster-level footprint. A standardized estimate of the formal error associated with WFAPT was made, and if this exceeded 100%, WFAPT was set to WFAPT:0. The formal error for the original (fixed pressure) water abundance estimate (WAPT) is stored on the data base. The formal error takes into account the number of missing IFOVs when constructing the raster-level averages. When dust is suspended in the atmosphere or clouds are in the field-of-view, the water column abundances derived here will underestimate the true water column abundance (see [DAVIES_1979]). The effects of hazes can be minimized for most periods by using only those rasters whose air mass < 5 or equivalent restrictions on the incidence and emission angles for the observation. See [JAKOSKY_ETAL_1988] for further details. Initially in the mission, orbit updates were done daily; later on, they were done only once per week. Therefore, the precise position of the spacecraft could not be determined accurately at all times. Uncertainty in the spacecraft location in turn leads to uncertainty in the latitude and longitude, and hence derived geometry parameters, of each MAWD observation included in this data set. The user should be aware of possible discrepancies in the position and geometry data contained in the data set. The data set contains the following fields related to confidence level (listed as the field name followed by a description. MISSING_IFOV Count of the number of instantaneous fields of view missing from the raster QUALITY The quality of geometry and calibration. For general use, constraining QUALITY <: 5 is recommended. 1 - Good data, as processed 2 - Lat/lon corrected by interpolation; surface elevation recomputed 3 - Surface elevation recomputed using database lat/lon 5 - Lat/lon updated with some uncertainty; still thought to be useful 6 - Lat/lon updated, but estimates are questionable 7 - Out-of-bounds (upper or lower) water amounts, set arbitrarily to 150.1 pm in original processing 9 to 13 - Various geometry problems: incorrect lat, lon, emission, or incidence 18 - Rasters with bad radiances or many data defects
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| CITATION_DESCRIPTION |
Citation TBD
|
| ABSTRACT_TEXT |
This data set consists of the raster-averaged radiant intensities and associated data parameters produced from data acquired by the Mars Atmospheric Water Detectors (MAWD) onboard the Viking Orbiters. The basic observations give temporal coverage spanning just over two martian years and variable, but extensive, spatial coverage of the planet. MAWD was a five-channel grating spectrometer measuring solar radiation reflected from the surface and atmosphere of Mars in and out of water vapor bands in the 1.4 micrometer spectral interval. The data set described here contains the solar reflected radiant intensities (i.e., radiances) measured by MAWD, derived water vapor column abundances, a derived '1.4-micrometer brightness', and ancillary data (e.g., viewing geometry, surface elevation and air mass). Column water vapor abundances were derived by comparing the reflected radiant intensities in three water vapor absorption bands to radiant intensities in the two interspersed continua observed air mass and then normalized by the air mass to obtain a vertical column abundance. A basic description of the instrument, its observational modes and its derived data products is given in [FARMER_ETAL_1977]. A description of the global and seasonal variation of water vapor on Mars, based on the complete MAWD observational record, is given in [JAKOSKY_FARMER_1982]. This data set was generated from the raster-level data base constructed during the Viking Mission on the original data processing system (IRPS: Infrared Processing System) by the MAWD Science Team, led by C. B. Farmer, JPL. Together with the instantaneous field of view (IFOV) radiances and geometry, the raster-level radiances, associated water column abundances and ancillary data have been archived at the NSSDC (NSSDC id 75-075A-03A, 75-083A-03A). Data from the final phase of the VO-1 mission were added, supervised by R. Zurek, JPL. Eventually, the data set was restructured, additional quality flags were introduced, and a second estimate of the water vapor column abundance (WFAPT, termed COLUMN_H2O_A in the data set) was added [by R. Zurek, JPL [JAKOSKY_ETAL_1988].]. The data base was restructured, while preserving key unique parameters, into a consistent format with the Viking Orbiter Infrared Thermal Mapper (IRTM) data [R. Mehlman, R. Zurek]. Both the MAWD and IRTM data sets were then accessible with the XXFUNC package. Further quality checking of the MAWD data was carried out by B. Jakosky, U. Colorado.
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| PRODUCER_FULL_NAME |
C.B. FARMER
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| SEARCH/ACCESS DATA |
Atmospheres Online Archives
Atmospheres Online Archives
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