Mars

The Mars Global Surveyor project has resumed scientific observations of the surface of Mars and has scheduled opportunities to image four selected sites: the Viking 1 and 2 landing sites, the Mars Pathfinder landing site and the Cydonia region.

Three opportunities to image each of the four sites using the spacecraft's high-resolution camera will take place over the next month, beginning on April 3 at 1:58 a.m. Pacific time, when Global Surveyor passes over the Viking 1 landing site. The spacecraft will next pass over the Viking 2 landing site at 1:37 p.m. Pacific time on April 3. On April 4, Global Surveyor will try to image the now-silent Mars Pathfinder spacecraft at 1:16 a.m. Pacific time. It will then capture a portion of the Cydonia region of Mars, location of the so-called "Face on Mars," on April 5 at 12:33 a.m. Pacific time.

Attempts to rephotograph the sites will occur during two additional opportunities falling about nine days apart. A detailed schedule of the imaging attempts is listed below. Uncertainties in both the spacecraft's pointing and the knowledge of the spacecraft's ground track from its navigation data will provide only a 30- to- 50-percent chance of capturing the images of each site.

All of the selected targets are located south of Global Surveyor's periapsis, or point of closest approach to the Martian surface. Shortly before the spacecraft reaches this point, the Global Surveyor spacecraft will rotate slightly so that when it nears the selected target, the camera's field-of-view will sweep across the target as the spacecraft flies south and rises away.

The spacecraft will begin transmitting to Earth data stored on its onboard solid-state recorders about seven hours after the images are acquired, concluding about three hours later. Currently it takes radio signals from Mars Global Surveyor about 20 minutes to travel from the spacecraft to Earth.

Data will be received at one of NASA's Deep Space Network tracking stations at Goldstone, CA, near Madrid, Spain or near Canberra, Australia, and then sent by satellite to NASA's Jet Propulsion Laboratory, Pasadena, CA. There the images, along with all of the rest of Global Surveyor's science and engineering data, are placed in the project database for access by flight controllers. This process takes only seconds for each bit of data. Consequently, the image data will not be available be on the ground until about 10.5 hours after they are acquired. Data received overnight will not be retrieved until 9 a.m. Pacific time on the following workday.

When image data are retrieved by camera operators, the information is assembled into "raw" images. Raw images may contain data errors or drop-outs introduced by noise in the telecommunications channel between the spacecraft and the ground, as well as very slight picture element variations inherent in the camera. This data processing takes about 30 minutes.

Raw images will posted on three web sites: JPL's Mars news site at http://www.jpl.nasa.gov/marsnews , the Mars Global Surveyor project home page at http://mars.jpl.nasa.gov , and NASA's Planetary Photojournal site at http://photojournal.jpl.nasa.gov . Information identifying the acquisition time, predicted center latitude and longitude of the target location, and the local solar time will accompany these images. Contrast enhancement will be performed by JPL's Multimission Image Processing Laboratory and posted on World Wide Web a few hours later. The Global Surveyor project home page also contains spacecraft orbital velocity and distance to the planet in real time.

Images of the Viking and Mars Pathfinder landing sites will not be posted until image enhancement and identification of the vehicles have been completed, because the small spacecraft will be at the limits of the camera's resolution. This process will take about 24 hours.

Mars Global Surveyor is part of a sustained program of Mars exploration known as the Mars Surveyor Program. The mission is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. JPL's industrial partner is Lockheed Martin Astronautics, Denver, CO, which developed and operates the spacecraft. JPL is a division of the California Institute of Technology, Pasadena, CA.

Mars Global Surveyor Imaging Schedule

First opportunity

Date Time

(UTC/Pacific) Orbit

Number Target Approximate

Internet

Posting

4-3-98 09:58/1:58 a.m. 216 Viking Lander 1 April 6

4-3-98 21:37/1:37 p.m. 217 Viking Lander 2 April 7

4-4-98 09:16/1:16 a.m. 218 Mars Pathfinder April 7

4-5-98 08:33/12:33 a.m. 220 Cydonia April 6 (mid-a.m.)

Second opportunity

Date Time

(UTC/Pacific) Orbit

Number Target Approximate

Internet

Posting

4-12-98 15:23/ 8:23 a.m. 235 Viking Lander 1 April 14

4-13-98 03:01/ 8:01 p.m. 236 Viking Lander 2 April 15

4-13-98 14:40/ 7:40 a.m. 237 Mars Pathfinder April 15

4-14-98 13:57/ 6:57 a.m. 239 Cydonia April 14 (mid-p.m.)

Third opportunity

Date Time

(UTC/Pacific) Orbit

Number Target Approximate

Internet

Posting

4-21-98 20:45/1:45 p.m. 254 Viking Lander 1 April 23

4-22-98 08:23/1:23 a.m. 255 Viking Lander 2 April 24

4-22-98 20:02/1:02 p.m. 256 Mars Pathfinder April 24

4-23-98 19:18/12:18 p.m. 258 Cydonia April 24 (mid-a.m.)


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