Curiosity finishes self-inspection, photographs Phobos
By David Szondy
September 16, 2012
NASA’s Mars rover Curiosity has limbered up its robotic arm, taken a good look at itself and has been given a clean bill of health. It’s now on the move as it starts its two-year mission of discovery on the Red Planet. On Thursday, it traveled 105 feet (32 m) as it seeks out its first rock for serious investigation. Meanwhile, the nuclear-powered explorer sent back images of Mars’s moon Phobos as it passed in front of the Sun.
Curiosity has covered 466 feet (142 m) of ground since its touchdown at Bradbury Landing on August 6. Since September 5, the rover has remained in one spot running its 7-foot (2.1 m) arm through its paces and giving itself a close visual examination.
The Mars Hand Lens Imager (MAHLI) seen above was key to Curiosity’s self-examination. Unfortunately, the camera couldn’t examine itself, so that job fell to the rover’s mastcam, which took this image. Part of Curiosity’s “hand,” MAHLI is basically a super magnifying glass for close-up, high-resolution imaging. In this case, its job was to inspect Curiosity bit by bit for any signs of damage or dust kicked up on landing. It was also used to evaluate how well the arm positioned its tools and hit its “teach” points, such as over the sample inlets to Curiosity's internal Chemical and Mineral (ChemMin) and Sample Analysis at Mars (SAM) laboratories.
Another “finger” of Curiosity’s hand is the Canadian-made Alpha Particle X-ray Spectrometer (APXS). The above image has been enhanced to show it as it would appear under earth-level light. The brightest days on Mars are equivalent to our twilight. So far, it’s been used mainly for taking atmospheric readings.
The APXS uses a pinch of radioactive material to analyze rocks by illuminating them with a spray of alpha particles, protons, and X-rays and the spectrometer measures the backscatter of alpha particles and x-rays. In order to calibrate the instrument, Curiosity is equipped with a 1.4 inches (3.5 cm) calibration target made of basalt from a New Mexico lava flow. This was chosen because it was strong enough to survive landing and its lack of sulfur, nickel and chlorine in its makeup, which is common in Martian dust so any contamination of the target by dust is easily detected.
So far, the APXS is working beyond expectations. "The spectrum peaks are so narrow, we're getting excellent resolution, just as good as we saw in tests on Earth under ideal conditions," said APXS principal investigator Ralf Gellert of the University of Guelph in Guelph, Ontario, Canada. "The good news is that we can now make high-resolution measurements even at high noon to support quick decisions about whether a sample is worthwhile for further investigations."
Should Curiosity detect any organic chemicals, a sign of possible life, Curiosity is designed to make sure that the readings aren’t due to instrument error on the part of the the rover’s SAM laboratory or earthly contamination. The circular area in the above image is a 2.5 inches (6.5 cm) foil-covered brick of organic check material, which the robotic arm will open and deliver to SAM inside Curiosity’s hull. The check material is laced with fluorine markers and if SAM detects any organic chemicals during the test that are not marked by fluorine, then the laboratory will be known to be contaminated by terrestrial organics. Curiosity carries five of these bricks.
This 3D image of Curiosity’s image calibration target isn’t meant to show that the explorer can shoot Hollywood blockbusters. Curiosity’s arm camera takes 3D images in order to provide mission control back at the Jet Propulsion Laboratory (JPL) in Pasadena, California with detailed images of rock samples and also acts as a form of depth perception for the rover. The latter is is very important when you’re moving around an extremely expensive arm a hundred million miles from the nearest garage and can’t afford to bump into anything.
The calibration target seen above is vital to making sure that Curiosity’s arm camera is working properly. Attached near the base of the arm, it works like a television test pattern and is used to make sure that Curiosity is sending back true images of what it sees. There is a palette of colors and a set of bar patterns to check depth adjustment.
The calibration target also includes a human face. In this case, that of President Abraham Lincoln on a United States penny. This provides a sense of scale, which is why geologists traditionally use coins in photographs. Portraits are also very good for capturing very fine details and are widely used by Earthling television broadcasters to calibrate cameras. However, JPL didn’t use just any old penny. They went for a 1909 VDB penny from the first year Lincoln pennies were minted and marked the centennial of Lincoln’s birth.
The results of all this fiddling calibration work can be seen in this image taken by the robotic arm of the Martian moon Phobos in transit across the disc of the Sun. Though Curiosity's mission is mainly geological, it can carry out other tasks as well.
To protect their delicate lens on landing or during dust storms, Curiosity’s cameras are equipped with transparent covers. Here we can see a trio of images taken by the MAHLI camera with the dust cover closed, open and closed again.
This above shot of the Martian surface was the first taken by the MAHLI camera with the dust cover open and shows the level of detail that it’s capable of recording.
Of particular importance to JPL was making sure that the sample inlet covers for Curiosity’s ChemMin and SAM laboratories were intact, operating properly and relatively free from dust and debris. As you can see in the above image, this was not an idle concern. The black flecks spread across Curiosity’s top deck are pebbles, sand and dust thrown up by the rockets of the sky crane as it deposited Curiosity on the Martian surface.
This close up of the inlet to Curiosity’s ChemMin laboratory shows the high resolution of the robot arm’s MAHLI camera as well as the particles of dust, sand and pebbles that the 2.67 inches (6.77 cm) inlet cover prevents from falling into the lab.
The above image shows the ChemMin laboratory inlet open. Curiosity’s arm uses its drill to collect powdered geological samples, which are then deposited into this inlet. Inside, the ChemMin lab analyzes the sample by passing x-rays through it and measuring their diffraction. Curiosity is the first Mars mission to carry an x-ray diffractor.
Curiosity’s self-examination was very thorough indeed. Not only did it send back images of its instruments, it also took detailed pictures of its wheels and undercarriage. This was more than mere thoroughness at work. Curiosity’s wheels also acted a its landing gear and it was important to make sure that nothing was damaged during touchdown.
Curiosity has certainly had a busy schedule since it landed. During its three-week shakedown it fired its rock-vaporizing laser, streamed back the first human voice from another planet, gave itself a software update and even wrote a message in the sands of Mars. Now the 4X4 sized explorer is ready to begin its two-year mission to seek out areas in Gale crater where life may have once or still could exist on Mars.