MSL Picture of the Day:T-34 Days: instruments: MastCam

MSL Picture of the Day:T-34 Days: instruments: MastCam

The Mastcam principal investigator is Michael Malin, a geologist who founded Malin Space Science Systems (MSSS) in San Diego, California, and has participated in NASA Mars exploration since the Mariner 9 mission in 1971–72. James Cameron is Co-Investigator of the MastCam. On a later date we will dedicate a full blog to the imaging magic of Michael Malin and his team.

The MastCam is actually a pair of cameras, with fixed focal lengths, near the top of the remote sensing mast, having its ‘eyes’ towering 2 meters above the Martian plains:
- MastCam34: the shorter focal length eye with a focal length of 34 millimeters, also offering a wider angle of vision
- MastCam 100: the longer, telephoto eye with a focal length of 100 millimeters

Mastcam 34 is a duplicate of Mastcam 100 except for the lens. Each camera includes refractive optics, a focus mechanism, a filter wheel, a charge-coupled device (CCD) sensor and associated electronics. The only external indication of which camera is which is that the front baffle opening for the Mastcam 100 is smaller than the front baffle opening of the Mastcam 34. Each camera can provide color images and high-definition video, and they can be combined for stereo views.
The mast is on the right side of the rover

Prior to the MSL being delivered to Kennedy Space Center for integration in the fairing of the Atlas V rocket, Michael Malin and his team had worked on two zoom flight units, plus one life test unit (LTU) to replace the MastCam 100 and 34. Unfortunately their optical performance, while reasonable over most of their zoom range, was not as good at 100mm as the MastCam100 system already at hand for MSL. MSSS and MacDonald Dettweiler and Associates (MDA) engineers worked long hours over the last half of 2010 in an effort to complete the systems in time. Eventhough the zoom lenses worked, they did not work quite as well at the longer focal lengths as the fixed focal length cameras that were ready for flight. Therefore Curiosity ended up with her fixed focus lenses.
MSSS will continue to pursue the development of these zoom systems, both to prove out the design and to make the hardware available for possible use on future missions. Perhaps next rover will have a zoom lenses on it.

How many megapixels are those cameras?
Only two megapixels. Amazing if one considers what the MPs on an average cell phone are. Nevertheless they are state of the art, besides having a more than state of the art team to command them. It is a bit like driving a porche does not make you the best chauffeur, but the best chauffeur driving an old, beaten up car can still do amazing things with it. The same holds for the cameras that are viewing Mars for us at present: superb ‘chauffeurs’ are in the command centers and therefore we have great confidence that the images MSL will send us will be all what we could hope for.

The right-eye Mastcam 100 will be able to reveal 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 34 provides broader context through a medium-angle lens. Each camera can acquire and store thousands of full-color images. Each is also capable of recording high-definition video. Combining information from the two eyes can yield 3-D views where the images overlap. Both cameras can focus on features at any distance from about 2 meters (6 feet) to infinity.

MastCam 100 can take 1200 by 1200 pixels square images where each pixel represents 7.4 centimeters (2.9 inches) on real Mars if the distance on the photo is 1 kilometer (0.6 miles). When MastCam 100 is used for close up images (still 1200 by 1200 pixels) each pixel will represent 150 microns (about 0.006 inch) if the distance of the object being taken is 2 meter (6.6 feet) away.  In laymen’s terms the camera provides enough resolution to read “ONE CENT” on a penny on the ground beside the rover. (Not that we expect any pennies laying around on Mars.)

Mastcam 34 can take images which show a three times wider field of view. MastCam 34 can taken 1200 by 1200 pixels images where each pixel represents 22 centimeters (8.7 inches) if the distance on the photo is 1 kilometer (0.6 mile) and 450 microns per pixel (0.018 inch) if the distance of the object is 2 meters (6.6 feet).

Compared to the PanCam of the Mars Exploration Rovers Spirit and Opportunity the MastCam 34 gives us 3.4 times higher spatial resolution than PanCam. And the MastCam 100 gives us 1.25 times higher spatial resolution than MER PanCam.

The MastCam’s lenses sit about 2 meters (6.5 feet) above ground level.
The eyes are 25 centimeters apart (10 inches), which is farther apart than the stereo eyes on earlier Mars surface robots.

Lucky for us (and for the scientists and engineers) the Mastcam 34 can record the full-color, full-circle panoramas which we have gotten used to from the Mars Exploration Rovers Spirit and Opportunity. Mastcam 34 will take 150 images in about 25 minutes showing everything from the nearby ground around Curiosity to the horizon to produce one panoramic image. The PanCam images measure 1024 by 1024 pixels.

The Mastcams will provide still images and video to study motions of the rover. Not for our enjoyment, although I know we will enjoy these movieclips, but for science, e.g. seeing how soils interact with wheels, and for engineering, e.g. aiding in the 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.

Video from the cameras is 1280 by 720 pixels (high definition) at four to seven frames per second, depending on exposure time.
This means that videos from the Curiosity cameras that we will view will actually be shot 6 to 3.5 times slower than the speed on which we are viewing them. NASA speeds them up for our ‘enjoyment’..

Malin Space Science Systems built four cameras for Curiosity in total. The two Mastcams and two other cameras:
- the Mars Hand Lens Imager (MAHLI, see MSL Picture of the Day:T- 31 Days on 5 July)
- the Mars Descent Imager. (MARDI, see MSL Picture of the Day:T- 27 Days on 9 July)

The four cameras from Malin Space Science Systems share several design features.
* Each camera uses a Bayer pattern filter, as found in many commercial digital cameras, for color imaging.
* The charge-coupled device (CCD) that detects each pixel of the image is covered with a grid of green, red and blue filters so that the camera gets the three color components over the entire scene in a single exposure.
This is a different method from what was used for color images from the earliers Mars landers (Phoenix) and rovers (Spirit and Opportunity), where a  series of exposures would be taken through different filters, later to be combined on Earth into color composites.
With this new system of taking color images we finaly see pictures in which the color closely mimics the way the average human eye sees the world.
* The cameras use Kodak CCD with an array of 1,600 by 1,200 active pixels.  The camera’s square field of view covers 5.1° over 1200 by 1200 pixels on the instrument’s 1600 by 1200 CCD.
All cameras have an eight-gigabyte flash memory.

Besides the affixed red-green-blue filter grid, the Mastcams have wheels of other color filters that can be rotated into place between the lens and the CCD. Filters for the 34 mm Mastcam are (in nanometers): 440, 525, 550, 675, 750, 865, 1034.. Filters for the 100 mm Mastcam are (in nanometers): 440, 525, 550, 800, 905, 935, 1035.

These include science spectral filters for examining the ground or sky in narrow bands of visible-light or near-infrared wavelengths. These science filters can be used for follow-up observations to gain more information about rocks or other features of interest identified in red-green-blue images.

The cameras are also capable to look directly at the sun using special, neutral density filters rotated before the lens. a 440 neutral density filter for the MastCam 34 and a 880 neutral density filter for the MastCam 100. This is set up to measure the amount of dust in the atmosphere. Important to know as dust in the atmosphere is a key part of the weather on Mars.

To keep the dust from accumulating on the color chips and the white-grey-balance reference chips a clever way was thought up: magnets to catch the dust as Martian dust is highly magnetic.

If you have always wondered what the colors on Mars truly would look like to you, the cameras on Curiosity have been built to give you ‘true Mars’, incorporating the effect that the redder than on Earth natural Mars lighting tends to be. All red coloring due to the dust in the Mars’ atmosphere. On Earth this reddening effect in the natural light occurs at sunset, coloring everything warm, orange. However your eyes would correct for this effect and to show you what that would look like the cameras even have the capability to do a white-balance calculation to adjust for the tint of this reddish martian lighting.

Both MastCams are capable of producing both true-color and white-balanced images.
* The focusing mechanisms on the cameras were built by MDA Information Systems Space Division, formerly Alliance Spacesystems, Pasadena, California.

Requirements of the cameras to be build (2006 workshop) were a large internal storage: 256 MByte SRAM, 8 GByte flash. That seems enough for lots and lots of new Mars vistas and close ups.
I can’t wait for the first one.

In the clean room at JPL, engineers gather around the base of Curiosity’s “neck” (the Mast) as they slowly lower it into place for attachment to the rover’s “body” (the Wet Electronics Box, or “WEB”)

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