20-APR-98 11:00 AM PDT
The Mars Surveyor Operations Project is proceeding with the implementation of its third and final cluster of targeted imaging at Mars. This cluster will again target the two Viking Lander sites, a refined Mars Pathfinder landing site, and a new area in Cydonia.
On Tuesday, April 21st, at 1:43 PM PDT and on Wednesday morning, April 22, at 1:22 AM PDT, MGS will again attempt to image the sites of the Viking Landers on two consecutive orbits. Recall that on the first attempt, Viking 1 was slightly outside the camera’s field of view. However, on the second attempt the site was in the image, but it was not possible to see the lander. The Viking 2 site has been covered with clouds on both previous attempts.
Then on Wednesday afternoon, April 22 at 1:00 PM PDT, MGS will again attempt to image the site of the Mars Pathfinder landing. This site was missed on the two previous attempts.
On Thursday afternoon at 12:17 PM PDT, MGS will again image a portion of the Cydonia region. Global Surveyor will again target to capture an image of the features known as "The City". This area contains features identified as "mounds", "city square", "pyramid" and the "fortress". The image will be targeted to capture portions of the "pyramid" and the "fortress", as well as "mounds".
As with the two previous images of the Cydonia region, the camera will be set to produce an image 1024 pixels wide so that the length of the image can be maximized to include as many features as possible. With a range from Cydonia to the spacecraft of 392 kilometers (244 miles), this will enable a resolution of 3.46 m/pixel (11.4 feet/pixel) and an image 3.5 km (2.2 miles) in width by 33 km (20.5 miles) in length.
The same probabilities of success of 30% to 50% will apply to each of these attempts based on navigation uncertainties and spacecraft attitude control performance. Experience with the first and second clusters of targeted images has shown that winter weather in the northern hemisphere of Mars at this time causes haze, dust storms, surface frost and heavy cloud cover to be significant factors in the success of seeing the targets clearly. The weather effects are not included in the probability of success estimates.
Results of the Cydonia imaging will be posted on the Internet, in the same manner as following the first and second observation attempts, at approximately mid-morning Pacific Time on Friday, April 24th. (When the playback of data from the spacecraft occurs overnight, as it does in this case, the image will be released shortly after the opening of business the following day.) If the landers are within the resulting images and can be identified, the image(s) containing it (them) will be released.