The left eye of the two-camera Mast Camera (Mastcam) instrument on NASA’s Mars rover Curiosity took the images combined into this mosaic of the rover’s upper deck. Image : NASA/JPL-Caltech/Malin Space Science Systems
Two digital color cameras riding high on the mast of NASA’s
next Mars rover will complement each other in showing the surface of Mars in
They are the left and right eyes of the Mast Camera, or
Mastcam, instrument on the Curiosity rover of NASA’s Mars Science Laboratory
mission, launching in late 2011.
The right-eye Mastcam looks through a telephoto lens,
revealing details near or far with about three-fold better resolution than any
previous landscape-viewing camera on the surface of Mars. The left-eye Mastcam
provides broader context through a medium-angle lens. Each can acquire
thousands of full-color images and store them in an eight-gigabyte flash
memory. Both cameras are also capable of recording high-definition video at
about eight frames per second. Combining information from the two eyes can
yield 3D views of the telephoto part of the scene.
Motivation to put telephoto capability in Curiosity’s main
science imaging instrument grew from experience with NASA’s Mars Exploration Rover
Opportunity and its studies of an arena-size crater in 2004. The science camera
on that rover’s mast, which can see details comparably to what a human eye can
see at the same distance, showed intriguing patterns in the layers of Burns
Cliff inside Endurance Crater.
“We tried to get over and study it, but the rover could
not negotiate the steep slope,” recalled Mastcam Principal Investigator
Michael Malin, of Malin Space Science Systems, San Diego. “We all desperately coveted a
telephoto lens.” NASA selected his Mastcam proposal later that year for
the Mars Science Laboratory rover.
The telephoto Mastcam, called “Mastcam 100” for
its 100-millimeter focal-length lens, provides enough resolution to distinguish
a basketball from a football at a distance of seven football fields, or to read
“ONE CENT” on a penny on the ground beside the rover. Its images
cover an area about six degrees wide by five degrees tall.
Its left-eye partner, called “Mastcam 34” for its
34-millimeter lens, catches a scene three times wider—about 18 degrees wide and
15 degrees tall—with each exposure.
Researchers will use the Mastcams and nine other science
instruments on Curiosity to study past and present environments in a carefully
chosen area of Mars. They will assess whether conditions have been favorable
for life and favorable for preserving evidence about whether life has existed
there. Mastcam imaging of the shapes and colors of landscapes, rocks and soils
will provide clues about the history of environmental processes that have
formed them and modified them over time. Images and videos of the sky will
document contemporary processes, such as movement of clouds and dust.
Previous color cameras on Mars have taken a sequence of
exposures through different color filters to be combined on Earth into color
views. The Mastcams record color the same way consumer digital cameras do: They
have a grid of tiny red, green and blue squares (a “Bayer pattern”
filter) fitted over the electronic light detector (the charge-coupled device,
or CCD). This allows the Mastcams to get the three color components over the
entire scene in a single exposure.
Mastcam’s color-calibration target on the rover deck
includes magnets to keep the highly magnetic Martian dust from accumulating on
portions of color chips and white-gray-balance reference chips. Natural
lighting on Mars tends to be redder than on Earth due to dust in Mars’
atmosphere. “True color” images can be produced that incorporate that
lighting effect—comparable to the greenish look of color-film images taken
under fluorescent lights on Earth without a white-balancing adjustment. A
white-balance calculation can yield a more natural look by adjusting for the
tint of the lighting, as the human eye tends to do and digital cameras can do.
The Mastcams are capable of producing both true-color and white-balanced
Besides the affixed red-green-blue filter grid, the Mastcams
have wheels of other filters that can be rotated into place between the lens
and the CCD. These include science spectral filters for examining the ground or
sky in narrow bands of visible-light or near-infrared wavelengths. One filter
on each camera allows it to look directly at the sun to measure the amount of
dust in the atmosphere, a key part of Mars’ weather.
“Something we’re likely to do frequently is to look at
rocks and features with the Mastcam 34 red-green-blue filter, and if we see
something of interest, follow that up with the Mastcam 34 and Mastcam 100
science spectral filters,” Malin said. “We can use the red-green-blue
data for quick reconnaissance and the science filters for target
When Curiosity drives to a new location, Mastcam 34 can
record a full-color, full-circle panorama about 60 degrees tall by taking 150
images in about 25 minutes. Using Mastcam 100, the team will be able to broaden
the swath of terrain evaluated on either side of the path Curiosity drives,
compared to what has been possible with earlier Mars rovers. That will help
with selection of the most interesting targets to approach for analysis by
Curiosity’s other instruments and will provide additional geological context
for interpreting data about the chosen targets.
The Mastcams will provide still images and video to study
motions of the rover—both for science, such as seeing how soils interact with
wheels, and for engineering, such as aiding in use of the robotic arm. In other
videos, the team may use cinematic techniques such as panning across a scene
and using the rover’s movement for “dolly” shots.
Each of the two-megapixel Mastcams can take and store
thousands of images, though the amount received on Earth each day will depend
on how the science team chooses priorities for the day’s available
data-transmission volume. Malin anticipates frequent use of Mastcam “thumbnail”
frames—compressed roughly 150-by-150-pixel versions of each image—as an index
of the full-scale images held in the onboard memory.
Malin Space Science Systems built the Mastcam instrument and
will operate it. The company’s founder, Michael Malin, participated in NASA’s
Viking missions to Mars in the 1970s, provided the Mars Orbiter Camera for
NASA’s Mars Global Surveyor mission, and is the principal investigator for both
the Context Camera and the Mars Color Imager on NASA’s Mars Reconnaissance
The science team for Mastcam and two other instruments the
same company provided for Curiosity includes the lead scientist for the
mast-mounted science cameras on Mars rovers Spirit and Opportunity (James Bell
of Arizona State Univ.); the lead scientist for the mast camera on NASA’s
Phoenix Mars Lander (Mark Lemmon of Texas A&M Univ.); James Cameron,
director of such popular movies as “Titanic” and “Avatar”;
and 17 others with expertise in geology, soils, frost, atmosphere, imaging, and
Mastcam 100 and Mastcam 34 were installed onto Curiosity in
2010. Until March 2011, a possibility remained open that they might be replaced
with a different design: two identical zoom cameras. A zoom camera has
adjustable focal length, to change from wider-angle to telephoto or vice-versa.
That design had been Malin’s original proposal. NASA changed the plan to two
different fixed-focal-length cameras in 2007 as a cost-cutting measure that
preserves the capability for meeting the science goals of the mission and the
instrument. The agency funded a renewed possibility for using the zoom-camera
design in 2010, but the zoom development presented challenges that could not be
fully overcome with enough time for required testing on the rover.
Mastcam 34 took images for a mosaic showing Curiosity’s
upper deck during tests in March 2011 inside a chamber simulating Mars surface
temperature and air pressure. Testing of the rover at NASA’s Jet Propulsion
Laboratory, Pasadena, Calif.,
will wrap up in time for shipping the rover to NASA Kennedy
in June. Testing and other launch preparations will continue there. The launch
period for the Mars Science Laboratory is Nov. 25 to Dec. 18, 2011, with
landing on Mars in August 2012.