During the morning hours of July 4, 1997, I experienced a strange sense of déjà vu as I sat glued to the television set watching live coverage of NASA’s first Mars landing attempt since the Viking missions. Almost 21 years before, in the early-morning hours of July 20, 1976 when I was 14 years old, I had watched live television coverage of the successful landing of Viking 1 and got to see the first images returned from the surface of Mars column by column (see “First Pictures: Viking 1 on Mars – July 20, 1976”). Now here I was at age 35 doing the same thing again, but for NASA’s Mars Pathfinder mission.
Diagram of the Mars Pathfinder lander as deployed on the surface. Click on image to enlarge. (NASA)
The second mission of NASA’s then-new Discovery program, the objective of the Mars Pathfinder mission was to prove that the development of “faster, better and cheaper” spacecraft was possible as well as provide a proof-of-concept for various enabling technologies such as an airbag-assisted landing on the Red Planet and rover technologies which were later employed by NASA’s highly successful Mars Exploration Rover missions launched six years later. In addition to the small 10.6-kilogram rover named Sojourner, the 360-kilogram Mars Pathfinder lander carried a modest science payload consisting of the Atmospheric Structure Instrument/Meteorology Package (ASI/MET) and a stereo camera called Imager for Mars Pathfinder (IMP).
The Imager for Mars Pathfinder (IMP) deployed on its mast. (NASA/JPL)
The Principal Investigator for the IMP was Peter H. Smith of the University of Arizona. The IMP consisted of a binocular camera mounted on top of a deployable, 80-centimeter tall open lattice mast mounted on top of the box at the heart of the lander which housed the instrument electronics assemblies. When deployed, the mast held the camer 1.5 meters above the ground. The camera head, which used a pair of stepper motors to point in azimuth and elevation, was roughly cylindrical in shape with a diameter of 10 centimeters and a length of 20 centimeters. The camera had a pair of apertures or “eyes” spaced 15 centimeters apart, to provide stereographic images, with each fitted with an f/18 lens with a focal length of 19 millimeters.
A diagram showing the components of the IMP. Click on image to enlarge. (NASA)
An internal set of folding mirrors focused the images from these pair of eyes onto a Loral 512×512 pixel CCD. Half of the array was covered by a metallic mask and was used as a readout zone for electronic shuttering. The active half of the array was split into two identical 248×256 pixel sub-arrays for each eye separated by a 12-pixel “dead zone” to minimize cross talk between the eyes. The data was digitized to 12-bits with the images taking about a minute to readout. The resulting field-of-view of each eye was 14.4°x14.0° with a pixel footprint of one millimeter at a range of a meter. Each eye had a 12-position filter wheel in the optical path of the lens. Four of the positions were fitted with filters for atmospheric investigations while another 7 held various color filters ranging from 440 to 1000 nanometers for multispectral imaging for geologic studies. The final filter wheel position held a diopter lens to allow the cameras to focus closeup on the camera tip plate to monitor a magnet mounted there.
Mosaic of Ares Vallis, created from high-resolution imagery from the Viking 1 orbiter, showing different landing ellipses based on various estimates, with a color inset of the Chryse Planitia region of Mars in the upper left (part of the Oxia Palus Quadrangle, MC 11, of Mars) showing the outflow channels. The blue “X” marks the location of the lander with respect to surface features identified in Viking orbiter images (located at 19.13°N, 33.22°W). Click on image to enlarge. (NASA/JPL)
Launched on December 4, 1996, Mars Pathfinder reached the Red Planet on July 4, 1997 landing at 16:56:55 UT (9:56:55 AM PDT). Renamed the Sagan Memorial Station after Carl Sagan who had passed away six month earlier, the lander had come down at 19.13°N, 33.22°W only 19 kilometers from its aim point where Ares Vallis empties into Chryse Planitia. Coincidentally, the landing site was only 45 kilometers away from (and well inside the landing ellipse for) the original landing site of Viking 1 – a site rejected after an initial survey from orbit in June 1976 as being too rough for this earlier lander. After coming to a complete stop, the Mars Pathfinder lander temporarily shut down its X-band transmitter (in order to conserve its battery) and three minutes later, started the process of retracting its airbags. A signal was received at mission control at the Jet Propulsion Laboratory at 11:34 AM PDT indicating that the procedure had been completed and the lander’s petals had opened 81 minutes after landing.
A panoramic mosaic of images of Mars Pathfinder and the surrounding terrain taken by the IMP between 4:00 and 4:30 PM PDT on July 4, 1997 (Sol 1 of the mission). Click on image to enlarge. (NASA/JPL)
After ground controllers received data via the low gain antenna at 2:22 PM PDT that the lander was healthy, commands were sent to unlatch the IMP and the high gain antenna. The IMP, with its mast still stowed, was then commanded to find the Sun to determine the lander’s orientation so that the high gain antenna could be properly pointed towards the Earth to start the transmission of images at 4:30 PM PDT. The first images included a panorama to determine how well the airbags had been retracted, stereo images of both sides of the petal holding the rover to verify it was safe to deploy the rover ramps, as well as a partial color panorama of the rover and the terrain beyond. The images showed a rock strewn rolling plain with distant landmarks visible allowing the position of the lander to be accurately tied to the high resolution Viking imagery of the region. The images also indicated that the airbag was still blocking the rover ramps so a procedure was started to retract them further. Images returned at 9:15 PM PDT showed that the airbags were now out of the way and the ramps were deployed 15 minutes later.
This 8-image color mosaic, which was part of the IMP’s “insurance panorama”, shows Sojourner after it was deployed on Sol 2. Click on image to enlarge. (NASA/JPL)
On Sol 2, the Sojourner rover drove onto the Martian surface and the IMP completed an “insurance panorama”, in case the camera ceased to function after the deployment of its mast. The IMP mast was successfully deployed on Sol 3 allowing the camera to image the surrounding terrain from a higher vantage point. Mars Pathfinder continued to operate far past its 30-Sol primary mission and was last heard from on September 27, 1997 during Sol 83. Attempts to recontact the lander continued for another five months with the mission officially declared over on March 10, 1998. In the end, the IMP returned over 16,500 images providing scientists with their first new, closeup look at the surface of Mars using new, state-of-the-art cameras. The 2.3 gigabits of data returned by Mars Pathfinder set the stage for the next round of surface exploration on the Red Planet which continues to this day.
This is a 360° color panorama was created using images returned by the IMP on Sols 8, 9 and 10. Different regions were imaged at different times over the three Martian days to acquire consistent lighting and shadow conditions for all areas of the panorama. Click on image to enlarge. (NASA/JPL)
Follow Drew Ex Machina on Facebook.
Related Video
Here is a media reel with video from key parts of the Mars Pathfinder mission:
Related Reading
“First Pictures: Viking 1 on Mars – July 20, 1976”, Drew Ex Machina, July 20, 2021 [Post]
General References
M. P. Golombek et al., “Overview of the Mars Pathfinder Mission: Launch through landing, surface operations, data sets, and science results”, Journal of Geophysical Research, Vol. 104, No. E4, pp 8523-8553, April 25, 1999
Paolo Ulivi with David Harland, Robotic Exploration of the Solar System Part 2: Hiatus and Renewal 1983-1996, Springer/Praxis, 2009
Mars Pathfinder Landing Press Kit July 1997, NASA Release 96-207, June 24, 1997