this info was required by a pioneer in the field of studying anomalous Mars images who created a BBS even b4 the days of the internet - following is a general idea of what was available... - minimal editing was done to protect involved parties

Nasa 1976 Viking Mission to Mars

By: Stamps Commerce Twp, Michigan

Digital Images from NASA Viking Orbiter Missions

Digital image data from the Viking Mission to Mars have become increasingly valuable to the planetary science community since the last images were acquired in 1980. To help meet this need, NASA's Planetary Data System (PDS), through the Geosciences Discipline Node at Washington University and the Image Node at the U.S. Geological Survey, Flagstaff, Arizona and the Jet Propulsion Laboratory, has created a digital archive of images acquired by the Viking Orbiter 1 and 2 spacecraft. The archive is being placed on compact read-only optical disk media (CD-ROM) for distribution to interested scientific research organizations, universities, and libraries.

The Viking Mission consisted of four spacecraft: two identical orbiters and two identical landers. The major scientific objective of the mission was to search for life on Mars. Several experiments on the landers were designed to address this objective. One of the Orbiter experiments was the Visual Imaging Subsystem (VIS), which acquired the images that comprise this archive.

The Viking Orbiter spacecraft operated in orbit around Mars from 1976 until 1980. Each Viking Orbiter was equipped with two identical vidicon cameras, called the Visual Imaging Subsystem (VIS). Each VIS camera consisted of a telescope, a slow scan vidicon, a filter wheel, and associated electronics.

Each compressed Viking Orbiter image file has a unique name constructed from the image id of that image. The general form of a compressed image file name is Fnnnxss.IMQ. Browse image file names have the same format, but with an extension of '.IBG'. The character 'F' at the beginning of the file name designates that 'nnnxss' is an image_id. The 'nnn' is the orbit in which the image was acquired. The 'x' indicates the spacecraft that acquired the image. The values of 'x' are usually A or S for Viking Orbiter 1 and B for Viking Orbiter 2. The letters C and D indicate images acquired by Viking Orbiter 1 and 2, respectively, before orbit insertion. The letter X indicates a Viking Orbiter 1 image acquired in an orbit with more than 100 images. The 'ss' is a sequence number for images acquired within one orbit.

Image File Name ID = 'nnnxss' The image identifier is a six character string to identify a Viking Orbiter image. The first three characters represent the orbit number; the fourth character is either an A or S for Viking Orbiter 1 or a B for Viking Orbiter 2. (There are a few cases where the fourth character is different from these values, for example when there are more than 100 images acquired during an orbit.) The last two characters represent the sequence number of the image within an orbit.

Interestingly, the most intriguing images have been the most difficult to acquire, and those are the Viking Lander images from the surface of Mars. So far, we have not located many of this type, but those that we have found are included in the disk series that we have released, and on my landline BBS where users and their home computers can download what we have found to date, and can upload what they have located. The BBS contains much more than is on the disks, and is frequently updated as new images are found, images are processed, and software versions are upgraded. There is no time limit, or upload download ratios on this BBS. Like the Jpl BBS, it is full open to the public and will handle 14,400 baud and down 24 hours a day.