FEBRUARY 15, 1965

       The areas on Mars that are expected to be photographed by the single television camera aboard Mariner IV have been determined by the National Aeronautics and Space Administration.

       Analysis of Mariner's flight path by engineers at the Jet Propulsion Laboratory, operated by the California Institute of Technology, pinpointed the areas.

       The target areas were outlined in a notice requesting amateur and professional astronomers to observe the areas with ground-based telescopes. The areas can be seen a number of times over the next several months before and after the closest approach of Mars to earth in early March.

       If the Mariner spacecraft is still operating normally when it flys by Mars, it will photograph the planet on July 14.

       Recording of the first picture will occur when the spacecraft is approximately 8400 miles above the Martian surface. The camera will sweep an area some 4000 miles long from the northern hemisphere, where it will be Fall, down through the southern hemisphere, where it will be Spring.

       When the first of up to 21 pictures is taken, Mariner's camera will be pointing at the northern Martian desert Amazonis. The camera's coverage will then sweep southeast below the Martian equator covering the Mare Sirenum, the southern desert Phaethontis, Aonius Sinus and into the terminator or shadow line. The spacecraft will be about 6300 miles above Mars for the final picture.

       The picture taking sequence will begin about 8:25 P. M. EST. Some 25 minutes later, the final picture will be taken and after another 21 minutes, Mariner will reach its point of closest approach to Mars at a distance of about 5,400 miles.

       The maximum ground resolution will occur near the middle of the photographic sequence when the camera is pointing nearly straight down toward the Martian surface in the area of the Mare Sirenum. At this point the photograph will cover an area approximately 150 miles on a side and the pictures should resolve prominent surface markings as small as two miles across.

       Not all of the 4000 mile strip to be photographed will be covered by pictures since only a limited number of pictures can be stored on the magnetic tape.

       The photographs will be stored in digital form on the tapes and played back to earth when Mariner has passed beyond Mars. Each picture will consist of about 250,000 bits of data and will be recorded at 10,700 bits per second.

       Transmission rate is 8 1/3 bits per second so, during the playback sequence, it will take about 8 hours and 20 minutes to transmit each picture to earth. Each picture transmission will be followed by 1 1/2 hours of engineering data on the condition of the spacecraft and then the next picture will be transmitted. It is planned to repeat the playback of the pictures at least twice.

       Mariner IV was launched November 28, 1964, and the general areas on Mars to be photographed were determined at the time of the mid-course correction to Mariner's flight path on Dec. 5. A requirement for the mid-course maneuver was to time Mariner's encounter period with Mars to coincide with the tracking period of the Goldstone Station of the Deep Space Net, in the Mojave Desert to insure maximum communication and command coverage.

       It has taken a period of detailed analysis of tracking data since the mid-course maneuver to determine precise target areas.

       The investigators for the TV experiment for NASA are Dr. R. B. Leighton, Professor B. C. Murray and Professor R. P. Sharp of the California Institute of Technology.