Data Set Information
DATA_SET_NAME MR9/VO1/VO2 MARS IMAGING SCIENCE SUBSYSTEM/VIS 5 CLOUD V1.0
DATA_SET_ID MR9/VO1/VO2-M-ISS/VIS-5-CLOUD-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set consists of a catalog of clouds observed in Mariner 9 and Viking Orbiter images. Seven 'cloud types' were defined according to easily observable objective morphologic criteria. The entire Mariner 9 and Viking Orbiter image data sets (approximately 7400 and over 50000 images, respectively) were examined at least twice, by two separate observers. Cloud occurrences were compiled by examining images for specific cloud morphologies, examining the same area at different times, utilizing limb images, and consulting photomosaics to determine the spatial relations of cloud obscurations. The data set contains details of the cloud occurrences and the images in which they were observed. There is a time gap of several years in the catalog -- the Mariner 9 data cover a time period from Ls (areocentric solar longitude) 293 degrees (Earth year 1972) through Ls 98 degrees (Earth year 1973), and the Viking Orbiter data cover a period from Ls 85 degrees (Earth year 1976) through Ls 140 degrees (Earth year 1980). These data have been used to infer near-surface wind directions, relative wind speed, static stability and humidity constraints, and qualitative atmospheric opacity conditions on a global basis over the martian year. Refer to [KAHN_1984] for further discussion of the data set derivation and analysis, and to [FRENCH_ETAL_1981; HUNT_ETAL_1981; KAHN_GIERASCH_1982; and KAHN_1983] for discussions of related analyses. This data set is composed of the following fields (listed as the field name followed by a description): SC_ID Spacecraft id IMAGE_ID Image id NORTH_AZ North azimuth in the image SUN_AZ Sun azimuth in the image SLANT_RANGE Slant range to image center PHASE_ANGLE Phase angle at image center SCALE_FACTOR Image scale factor (km/pixel) at image center FILTER_NO Filter through which the image was taken SOL_LON_PER Areocentric solar longitude at spacecraft periapsis CTR_PT_LAT Latitude on surface of image center point CTR_PT_LON Longitude on surface of image center point LOCAL_TIME Local time at image center point (expressed as 1/24 of a local day) CLOUD_TYPE 1 - Lee wave cloud 2 - Wave cloud 3 - Plume 4 - Streak cloud 5 - Cloud street 6 - Localized Fog 7 - Haze TYPE_CERTAIN Certainty of type identification: 1 - very certain 2 - Probable 3 - Not very certain WIND_DIR Apparent wind direction (measured counter-clockwise from a line between the center and right edge of the image) DIR_CERTAIN Certainty of determination of the wind direction 1 - Very certain 2 - Ambiguous by 180 degrees 3 - Ambiguous by less than 90 degrees 4 - Unknown HAZE_OPACITY For cloud type 7, indicates the haze opacity 1 - Thin (features clearly seen) 2 - Partial Obscuration 3 - Opaque HAZE_QUALITY For cloud type 7, indicates if haze was uniform to the edge of the image LIMB_POS For cloud type 7, indicates if the limb was in the image
DATA_SET_RELEASE_DATE 1989-11-01T00:00:00.000Z
START_TIME 1971-01-01T12:00:00.000Z
STOP_TIME 1980-01-01T12:00:00.000Z
MISSION_NAME MARINER71
VIKING
MISSION_START_DATE 1968-06-01T12:00:00.000Z
1975-08-20T12:00:00.000Z
MISSION_STOP_DATE 1973-06-01T12:00:00.000Z
1983-02-01T12:00:00.000Z
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MR9
VO1
VO2
INSTRUMENT_NAME IMAGING SCIENCE SUBSYSTEM
VISUAL IMAGING SUBSYSTEM - CAMERA A
VISUAL IMAGING SUBSYSTEM - CAMERA B
INSTRUMENT_ID ISS
VISA
VISB
INSTRUMENT_TYPE CAMERA
NODE_NAME Planetary Atmospheres
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Overview : There are about 16500 haze events (cloud type 7) and over 1400 occurrences of other cloud types. In 5-7% of the cases, the cloud morphology was sufficiently unclear for observers to disagree on the cloud type. In these instances a third observer helped to decide upon the designation. Errors exist in the identification of cloud streets (cloud type 5) at high northern latitudes, as the similar appearance of cloud streets and fields of sand dunes made identification difficult. Note that the few observed occurences of 'spiral clouds' (see [GIERASCH_ETAL_1979]) are catalogued as streak clouds (cloud type 4). The clouds in each image were counted independent of possible occurrence of parts of clouds in adjacent images. It should also be noted that spatial and temporal imaging coverage is very sparse, so to make a fair evaluation of the variation of cloud occurrence with season and/or location, spacecraft imaging coverage effects must considered. Refer to [KAHN_1984] for further discussion of the data set derivation and analysis.
CITATION_DESCRIPTION Citation TBD
ABSTRACT_TEXT This data set consists of a catalog of clouds observed in Mariner 9 and Viking Orbiter images. Seven 'cloud types' were defined according to easily observable objective morphologic criteria. The entire Mariner 9 and Viking Orbiter image data sets (approximately 7400 and over 50000 images, respectively) were examined at least twice, by two separate observers. Cloud occurrences were compiled by examining images for specific cloud morphologies, examining the same area at different times, utilizing limb images, and consulting photomosaics to determine the spatial relations of cloud obscurations.
PRODUCER_FULL_NAME RALPH KAHN
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