Curiosity: MAHLI put through its paces

September 7th through 9th saw the robot arm systems go through a range of “reach tests”  which also allowed Curiosity it complete another series of “firsts” from Mars as the Mars Hand Lens Imager (MAHLI) was used to capture a range of images of the rover to help with calibrating the system and to check-out Curiosity’s condition. All of these images were taken with the protective cover on MAHLI’s lens in the open position, and revealed the clarity with which the system can capture images.

There was a slight delay in progress on Sol 31 (Sept 6th), after a temperature reading from the arm caused Earthside concerns and the cancellation of planned activities while the matter was investigated and successfully resolved. Sol 32 (Sept 7th) saw the tests planned for the 6th Sept successfully completed, which included the capture of the images of the rover’s mast and the turret on the end of the robot arm I’ve previously reproduced here. A series of vibration tests were also carried out, designed to characterise the function of the sample processing device in the turret (the vibrations will cause the system to act like a sieve, separating-out very fine Martian surface material out from the rougher samples prior to delivery to the on-board science systems, CheMin and SAM).

The reach tests for the robot arm are designed to test the arm based on a range of calibration motions carried out on Earth intended to approximate how the arm should work on Mars. The tests are important because the arm, with the mass of the turret on the end, has only been operated in Earth’s gravity and engineers need to confirm that the arm is actually functioning as anticipated in the lower Martian gravity environment and after both an 8-month cruise through interplanetary space and the rough dynamics of the EDL phase of the mission. Adjustments carried out as a result of the reach tests will allow the arm and turret to be operated with the degree of precision required for the forthcoming science elements of the mission.

The Trivia Report I Forgot

On some of these MSL reports, I’ve published a small piece of trivia about the mission. One that I had lined-up, but then missed Pressing, was that fact that among all the science hardware on Curiosity there is … a 1909 Lincoln VOB penny.

MAHLI calibration target, complete with the first coin on Mars, a 1909 Lincoln penny

The penny is part of the calibration target for MAHLI, which is mounted on the front of the rover’s body. The target also includes colour chips, a metric standardised bar graphic, and (just below the penny) a stair-step pattern for depth calibration.

The penny itself is a nod to geologists’ tradition of placing a coin or other object of known scale as a size reference in close-up photographs of rocks, and it gives the public a familiar object for perceiving size easily when it will be viewed by MAHLI on Mars. The coin  was supplied by MAHLI’s principal investigator, Ken Edgett, and was minted to mark the centennial of Abraham Lincoln’s birth.

The Lincoln penny seen on Mars by MAHLI; note the fine film of Martian dust on the coin. “Joe the Martian” can be seen above the penny & inset. The main image was captured with MAHLI some 5cm (2 inches) from the target, and on a low resolution setting

Also on the calibration target is an image of “Joe the Martian”. This is also from Ken Edgett, and is actually his own creation, first drawn when he was nine years old when the NASA Viking missions in the 1970s inspired him to want to become a planetary researcher. The character was later used in a children’s science periodical, Red Planet Connection when Edgett directed the Mars outreach program at Arizona State University in the 1990s.

Both the penny and the character are designed to engage public interest in the mission, and both will be imaged throughout Curiosity’s operations on Mars, allowing people to see how weathered they become over time due to exposure to the Martian environment.

Taking a Look Underneath

On Sol 34 (Sept 9) MAHLI was used to take a series of images looking underneath the rover’s belly, allowing engineers to take a first-hand look at the overall condition of the wheels and underside of the vehicle and confirm there is no hidden damage which might cause problems later.

Curiosity’s wheels – note the Morse code JPL cut-outs – with “Mount Sharp” as a backdrop

These images also help demonstrate the extreme flexibility of MAHLI, which can image objects from as close as 2.1 cm (just under an inch) right out to infinity, allowing it to be used for close-in precise work related to surface science, and for producing more general images which can be used in a range of activities from confirming the rover’s status through to helping to plan for the drive to “Mount Sharp”.

Taken together, the MAHLI images are remarkable because no other planetary or robotic mission has been able to image itself so comprehensively. Being able to do so not only assists engineers in assessing the rover’s condition throughout the mission, it helps to further engage public interest in what Curiosity is doing by “personalising” the images it can return from Mars.

MAHLI mosaic of Curiosity’s underside. The four “eyes” at the top centre are the rover’s forward Hazcams, used in vehicle navigation, looking to the front and to the left / right of the rover’s path

Curiosity reports in this blog

Images courtesy of NASA / JPL.


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