Data Set Information
DATA_SET_NAME VL1/VL2 MARS LCS EXPERIMENT DATA RECORD V1.0
DATA_SET_ID VL1/VL2-M-LCS-2-EDR-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Dataset Overview : The imaging system on the Viking Landers consisted of two identical cameras. These cameras operated throughout the mission and returned nearly 6600 images. This dataset includes the Experiment Data Record (EDR) version of all available images acquired on Mars by the Viking Lander imaging systems. This EDR dataset is the primary record of lander image data as it was received on Earth. EDR images were originally distributed to lander imaging team members and to NSSDC as photoproducts and digitally on 9-track magnetic tapes. The images in this dataset have not been processed in any form other then generating and attaching PDS labels and histograms to the original EDR data. This dataset also includes documentation about the imaging system and radiometric and geometric calibration of the image data; browse versions of the EDR images; and metadata about the images in a format suitable for loading into spreadsheet or DBMS programs. Full quantitative use of Viking Lander image data requires an understanding the radiometric and geometric properties of the Viking Lander cameras. EDR pixel values can be converted to radiance or reflectance at the sensor using the calibration data available with this dataset. Since a Viking Lander image was acquired by a single diode with a linear response, the radiometric calibration is basically a linear scaling of pixel values that is dependent on the diode, gain and offset, and time (i.e., Mars-Sun distance). Additional corrections can be made for atmospheric effects. The radiometric calibration data available with this dataset are based on pre-flight testing. In-flight calibration measurements (internal calibration images) are included in this dataset since they are part of the original EDR dataset. Stereo imaging (viewing the same spot with both cameras) can be used to extract the 3-dimensional location of objects. Three-dimensional measurements can be used to construct topographic maps of the landing sites[Liebes, 1982]. Science Objectives : This section outlines the scientific objectives of the imaging experiment and describes the imaging sequences used to investigate these objectives. The specific intent for acquiring each image is given by the NOTE keyword of the PDS label. The major scientific objectives of the Viking Lander imaging investigation were to analyze the geology, cartography, meteorology, and biology of the landing sites [Mutch et al., 1972]. Geologic studies included characterizing the morphology of rocks, soils, and other features from texture and color, determining the size distribution of rocks, and understanding sediment transport. Cartographic studies involved mapping features at the landing sites, measuring surface topography, and determining lander location by comparing features seen in both lander and orbiter images. Meteorological investigations with Viking Lander images determined atmospheric aerosol properties (abundance, size, composition, and distribution) and searched for evidence of dust and condensate clouds. Biological studies with Viking Lander image data consisted of searching for evidence of living things [Levinthal et al., 1977b]. Arvidson et al. [1989] review the major results of the lander imaging investigations. Imaging sequences during the Primary Mission focused on: A) characterizing the surface and atmosphere at the landing sites; B) monitoring the sites for change; and C) supporting other experiments and sampling activities. Both landing sites were imaged with high resolution diodes during both the morning and afternoon. At VL2, a noon-time high resolution set of images were also acquired because of the longer Primary Mission. These high resolution images have been assembled into a set of mosaics [Levinthal and Jones, 1980]. The high resolution mosaics were the primary images used to generated systematic topographic analyses. The scene at both sites was also imaged in color at noon-time, and selected areas were imaged with the three infrared diodes. Furthermore, a portion of the scene was imaged in the high resolution color mode (low resolution color diodes with high resolution stepping). Several types of image sequences were acquired for atmospheric studies. The sun diode was used to determine atmospheric optical depth [Colburn et al., 1988]. Aerosol distribution was analyzed from twilight rescan images were the sky was imaged in a color rescan mode at dawn and dusk. In another atmospheric sequence, known as a sky brightness sequence, images of the sky were taken at different azimuths from the Sun. Scan verification and internal calibration images were periodically acquired to monitor the health of the cameras. Several sequences were acquired to search for variable features using rescan images and by repeatedly imaging the same areas. A series of images were collected to study the photometry of the surface. Image sequences supported several other lander experiments. Magnets on the lander and surface sampler backhoe were imaged periodically for the magnetic properties investigation. Images of spacecraft parts, trenches, and surface sampling activities were taken for the physical properties team. Images of sampling sites before and after sampling, including color and stereo images, were taken to support the planning and collection of samples. Images were also taken of the entry ports of the sampling experiments to check whether the ports opened after landing and to support sample collection. Problems with the surface sampling system were also analyzed with special images. During the Extended Mission and beyond, the emphasis of imaging shifted to: A) monitoring the surface and atmosphere through the Mars seasons; B) supporting other lander investigations; and C) performing special experiments. Camera health was monitored throughout the Extended Mission. Surface monitoring included periodically looking at disturbed areas (trenches and soil piles) and undisturbed areas (e.g., drifts) for movement and change. Images were also acquired to search for evidence of sediment deposition. During the winter season, the spacecraft and surface at VL2 were monitored for frost formation. Images, known as repro images, were acquired to match the lighting conditions of Primary Mission images so that subtle changes could be detected without complications from lighting differences. Jones et al. [1981] and Wall and Ashmore [1985] have image lists sorted by sun position to identify such repro images. Atmospheric studies during the Extended Mission continued with optical depth, twilight rescan, and sky brightness sequences. Some of the special imaging sequences of the Extended Mission included images to search for fog and ozone, images for photometric studies, and rescan images to detect the passage of the shadow of Phobos over VL1.
DATA_SET_RELEASE_DATE 1997-04-01T00:00:00.000Z
START_TIME 1976-01-01T12:00:00.000Z
STOP_TIME 1982-01-01T12:00:00.000Z
MISSION_NAME VIKING
MISSION_START_DATE 1975-08-20T12:00:00.000Z
MISSION_STOP_DATE 1983-02-01T12:00:00.000Z
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID VL1
VL2
INSTRUMENT_NAME CAMERA 1
CAMERA 2
INSTRUMENT_ID CAM1
CAM2
INSTRUMENT_TYPE CAMERA
NODE_NAME Imaging
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : The original EDR dataset was produced by the Viking Project and Lander Imaging Team. Levinthal et al. [1977a] explains the processing done to produce the original EDR images. Initial EDR processing included selecting and merging the best available data recorded at one or more DSN stations. After merging several playbacks, some imaging data were still not extracted from the telemetry stream because of noise in the data identification tags. Thus, special purpose software searched the telemetry stream to identify and extract imaging data with noisy tags. In some cases, this secondary processing greatly increased the amount of data recovered from the telemetry stream. Even with the secondary recovery, the EDR data contained random noise and missing lines. Random noise was usually due to transmission errors. Missing scan lines were filled with zero valued pixels. Missing data appear as black vertical lines in the image since the primary scan direction was vertical. As noted in the previous section, the camera voltage signal was digitized on the spacecraft to a 6-bit integer number (possible values between 0 and 63). However, the maximum brightness value output from the camera was 62 due to limitations of the system. As part of the standard EDR processing the original 6-bit value was converted to an 8-bit integer number by multiplying the 6-bit values by 4. These 8-bit values are the data archived in this dataset. Data Coverage and Quality : Several steps were taken to insure that the best available image data and label information were included in this dataset. The primary source of digital image data was the Viking Lander Imaging Team set of EDR 9-track magnetic tapes at Washington University. The data from these tapes were transferred to 8-mm tape and then to CD-WO before this archive was made. Since the original EDR files did not contain histogram or checksum values, automated data validation could not be done. Instead, each digital image was visually inspected and compared to a photoproduct version of the image. This check insured that the file contained the correct image data and that there were no obvious errors, such as missing or corrupted data. In a few cases errors were detected and a replacement image was obtained from the EDR set at JPL. The original EDR image files were stored in a VICAR format with metadata attached in a VICAR label. These metadata were used to populate the PDS label. Label parameters were checked for acceptable values and corrected if necessary. Catalogs [Tucker, 1981; Jones et al., 1981; Wall and Ashmore, 1985] and planning notes produced by the Lander Imaging Team were used to determine the purpose for acquiring a given image. This information was added to the PDS label as a NOTE field.
CITATION_DESCRIPTION Guinness, E. A., VL1/VL2 MARS LCS EXPERIMENT DATA RECORD V1.0, VL1/VL2-M-LCS-2-EDR-V1.0, NASA Planetary Data System, 1997
ABSTRACT_TEXT The imaging system on the Viking Landers consisted of two identical cameras. These cameras operated throughout the mission and returned nearly 6600 images. This dataset includes the Experiment Data Record (EDR) version of all available images acquired on Mars by the Viking Lander imaging systems. This EDR dataset is the primary record of lander image data as it was received on Earth. EDR images were originally distributed to lander imaging team members and to NSSDC as photoproducts and digitally on 9-track magnetic tapes. The images in this dataset have not been processed in any form other then generating and attaching PDS labels and histograms to the original EDR data. This dataset also includes documentation about the imaging system and radiometric and geometric calibration of the image data EDR images for loading into spreadsheet or DBMS programs.
PRODUCER_FULL_NAME EDWARD A. GUINNESS
SEARCH/ACCESS DATA
  • Geosciences Web Services
  • Atlas
  • Geosciences Web Services
  • Geosciences Online Archives
  • Imaging Online Data Volumes (JPL)
  • Imaging Online Archives (USGS)
    		•