NSSDCA ID: PSPG-00786
Availability: Archived at NSSDC, accessible from elsewhere
This description was generated automatically using input from the Planetary Data System.
Dataset Overview ================ The imaging system on each Viking Lander consisted of two identical cameras. These cameras operated throughout the mission and, together, the VL1 and VL2 camera systems 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 way other than by 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 of 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[LIEBES1982]. 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 [MUTCHETAL1972]. 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 [LEVINTHALETAL1977B]. ARVIDSONETAL1989 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. These high resolution images have been assembled into a set of mosaics [LEVINTHAL&JONES1980]. The high resolution mosaics were the primary images used to generated systematic topographic maps [LIEBES1982]. 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 [COLBURNETAL1988]. Aerosol distribution was analyzed from sky images obtained in a color rescan mode at dawn and dusk (twilight rescan). 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. Images were also obtained to study the photometry of the surface. Image sequences supported several other lander investigations. Images were also taken of the sample delivery ports of the Biology, GCMS, and XRFS experiments to check whether the ports opened after landing and to support sample collection. Sampling sites were imaged before and after sampling, including color and stereo images, to support the planning and collection of samples. 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. 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. JONESETAL1981 and WALL&ASHMORE1985 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. These data are available on-line from the Planetary Data System (PDS) at: http://pds-geosciences.wustl.edu/GEO/vl1_vl2-m-lcs-2-edr-v1/vl_0001/
Questions and comments about this data collection can be directed to: Dr. David R. Williams
Name | Role | Original Affiliation | |
---|---|---|---|
Prof. Raymond E. Arvidson | Data Provider | Washington University | arvidson@wunder.wustl.edu |
Dr. Edward A. Guinness | General Contact | Washington University | guinness@wustl.edu |