The IRPS database, which was the original source for the image locations used in constructing the footprint pages and the camera parameters summarized graphically herein. (The closest WWW descendants are the PDS Catalog and the form search in the Mars Navigator.)

The database is accessed through a TELNET connection. The data ultimately used in this atlas was downloaded several years ago with a custom-written client that used a TELNET connection to the PDS node at Washington University St. Louis to request all the Viking Orbiter image data.

A complete list of the parameters contained for each image in the IRPS database (which also covers Voyager and other missions) follows. The descriptions were taken from their entries in the IRPS database itself.

Each element is linked to its entry in PDS's official Planetary Science Data Dictionary, which gives a more detailed and generally more general definition, including ranges and possible values. Keep in mind that the definitions and list of possible values, apply to all of PDS's datasets, not just Mars images.

Emission_angle: The angle between the local surface normal and the surface to spacecraft vector. The emission angle varies from 0 degrees when viewing the subspacecraft point to 90 degrees when viewing the limb of the target body.
Exposure_duration: The time between the opening and closing of the camera shutter.
Filter_name: The common name given to a particular filter. The name usually refers to the wavelength range covered by the filter.
Filter_number: A number that identifies a particular filter. It could be the position of the filter on a filter wheel.
Image_id: The image_id is usually a composite of several pieces of information about an image. The format is mission dependent.
Image_number: A value obtained from the spacecraft clock count. The image number is a another commonly used identifier for an image.
Image_time: The time when an image was acquired.
Incidence_angle: The angle between the local surface normal and the surface to Sun vector. The incidence angle varies from 0 degrees when viewing the subsolar point to 90 degrees when viewing a terminator.
Instrument_mode_id: An instrument dependent designation of an operating mode.
Instrument_id: An abbreviated name or acronym that identifies an instrument. The instrument id is not the unique identifier since the same id can be used for instruments on different spacecraft.
Latitude: The latitude at the center of an image. Latitude, measured in degrees, varies from -90 at the south pole to +90 at the north pole.
Local_time: The local time of day at the center of an image, measured in local hours. A local hour is one twenty-fourth of a local solar day.
Longitude: The longitude at the center of an image. Longitude varies from 0 to 360 degrees. Longitudes are measured in the direction opposite to the rotation. That is, longitude inceases to the west for prograde rotation and to the east for retrograde rotation.
North_azimuth: The angle between a line from the image center to the north pole of the target body and a reference line in the image plane. The reference line extends from the image center to the middle right edge of the image. The angle increases in a clockwise direction.
Orbit_number: The number of orbits around the target that a spacecraft has made since orbit insertion.
Phase_angle: The angle between the surface-Sun and surface-spacecraft vectors. Phase angle varies from 0 to 180 degrees.
Scaled_image_height: The distance on the target body surface between the upper middle and lower middle points of the image.
Scaled_image_width: The distance on the target body surface between the left middle and right middle points of the image.
Scaled_pixel_width: The size of a picture element (pixel) projected onto the surface of a target body.
Spacecraft_altitude: The distance from the spacecraft to the subspacecraft point.
Slant_distance: The distance from the spacecraft to the point on the target body surface at the center of an image.
Solar_longitude: The angle between the target body to Sun vector at the time of interest and the target body to Sun vector at vernal equinox.
Spacecraft_id: A synonym or mnemonic for the name of a spacecraft which is unique to a given spacecraft.
Subspacecraft_azimuth: The angle between a line from the image center to the subspacecraft point and a reference line in the image plane. The reference line extends from the image center to the middle right edge of the image. The angle increases in a clockwise direction.
Subspacecraft_latitude: The latitude of the subspacecraft point. The subspacecraft point is that point on the target body surface directly beneath the spacecraft.
Subspacecraft_longitude: The longitude of the subspacecraft point. The subspacecraft point is that point on the target body surface directly beneath the spacecraft.
Subsolar_azimuth: The angle between a line from the image center to the subsolar point and a reference line in the image plane. The reference line extends from the image center to the middle right edge of the image. The angle increases in a clockwise direction.
Subsolar_latitude: The latitude of the subsolar point. The subsolar point is that point on the target body surface directly beneath the Sun.
Subsolar_longitude: The longitude of the subsolar point. The subsolar point is that point on the target body surface directly beneath the Sun.
Target_name: The name of a planetary body (i.e., planet or satellite).
Time_from_closest_approach: The time before or after closest approach to a target body. Negative values are used for times before closest approach and positive values for times after closest approach.
Target_center_distance: The distance between the spacecraft and the center of the target body.
True_anomaly_angle: The angle between the radius vector of an orbiting body and its periapsis vector. It is measured counterclockwise from periapsis.