Rollin’ rollin’ rollin’

Rollin’, rollin’, rollin,
Though the plains are dusty

Keep that rover movin’

Rocks and wind and cold nights
Crossing that ol’ crater
On your way to Glenelg now, in style.
All things you’re doin’,
Sampling, scraping, dating
Will help our understanding of Mars.

(With apologies to Ned Washington!)

Over the course of the last several days, NASA has completed initial calibration and characterisation of Curiosity’s robot arm and initial testing of several of the turret-mounted scientific instruments.

These tests have included discovering the arm’s range and accuracy of movement in the low Martian gravity and temperature environs, as well as commissioning the turret-mounted Mars Hand Lens Imager (MAHLI) camera and the Alpha Particle X-Ray Spectrometer (APXS) which is designed to determine the elemental composition of a target rock. Both are now all but cleared for science operations, although some further tests are planned.

On September 11th, Sol 36, the arm went through a series of “reach tests” using MAHLI to ensure that the arm can accurately position equipment over inlet ports on the rover’s body for the transfer of materials gathered from the surface of Mars.

Open wide! The CheMin sample inlet port, imaged by MAHLI on Sol 36. The 3.5cm (1.4 in) diameter  mesh-covered funnel will be used to supply Martian “fines” to the CheMin spectrometers for analysis

The Canadian-made APXS has previously been used to gather atmospheric readings, but the tests performed on September 10th, Sol 35, marked its first use on a solid target, using a calibration target mounted on the rover. The results showed APXS to be in excellent health. “The spectrum peaks are so narrow, we’re getting excellent resolution, just as good as we saw in tests on Earth under ideal conditions,” Ralf Gellert, the principal investigator for APXS reported. “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.” This latter point is important, as X-ray detectors best work cold, and so was thought that APXS might find the midday periods of a Martian Sol a little too warm to produce reliable results.

APXS imaged by the 34mm Navcam on Sol 32 (September 7th), during initial visual check-outs of the arm and turret systems. This image confirmed APXS was not caked with dust blown up by the Descent Stage motors during Curiosity’s arrival on Mars.

After its initial check-outs, MAHLI was further tested in its ability to produce 3D images of surface objects, again using the calibration target mounted on the front of the rover. MAHLI is the second imaging system Curiosity carries that is capable of producing colour 3D images, the other being the Mastcam system, which was tested prior to the rover departing Bradbury Landing. Both systems produce 3D images through accurate positioning of the cameras, either by manoeuvring the robot arm (for MAHLI) or the entire rover (for Mastcam).

Transit of Phobos

Earlier this year, I covered the Transit of Venus, an astronomical event only visible from Earth every 105 or 121 years. Mars has similar events, which include transits of the Earth across the face of the Sun and, more particularly, transits of its own small moons, Phobos and Deimos. Transits of Phobos occur twice every Martian year, and on Sol 37 (September 12th), Curiosity’s Mastcam was used to capture images of a Phobos transit. The full-resolution images from this are liable to take a few days to download and be processed, but the plan is to produce a movie of the transit from the images captured.

A raw (unprocessed) low-resolution image of the transit of Phobos – the 11km wide moon, some 6,000km above the surface of the planet can just be seen on the edge of the solar disk

Next Stop: Glenelg – or a rock

With the arm characterisation tests now all but complete, Curiosity was ordered to resume its drive towards Glenelg, an area of Gale Crater some 400 metres from Bradbury Landing. The drive commenced on Sol 38 (September 13th), when the rover completed a drive of 32 metres, a further increment in the daily distance covered as confidence is gained in Curiosity’s autonomous driving capabilities. Even so, it will still be another few weeks before the rover arrives at Glenelg, and the drive may again be interrupted if a suitable rock candidate is identified for direct in situ testing of APXS and MAHLI. If deemed suitable, the rock may also be used to test the rover’s turret-mounted drill, although testing of this may be held-over until Glenelg is reached towards the middle of October.

David Oh from the MSL team provides a superb summary for the week, and insight into working as a part of the Curiosity team.

Curiosity reports in this blog

Mission Trivia

Curiosity has now driven142 metres (466 feet) since its arrival on Mars.

Images courtesy of NASA / JPL.


4 thoughts on “Rollin’ rollin’ rollin’

  1. It should be pretty obvious. but they have that track visible to the cameras in orbit with that sharp turn in it. They have a visible mark with known dimensions on the surface of Mars, and a satellite taking photographs of it.

    We’re not just seeing the Curiosity instruments being tested and calibrated. There’s a calibration target for the orbiting cameras.


    1. HiRISE is already perfectly calibrated :).

      Its been in operation since 2006, and has had plenty of opportunities (including Opportunity, first captured on October 6th, 2006, and Spirit’s landing platform, which it also imaged) to be precisely calibrated against surface objects using visual means. Curiosity’s tracks are potentially of greater value in observing the effective of wind erosion on surface features over time, and the function of wind in general within the bowl of Gale Crater. Potentially very relevant given the debate as to how the mound NASA call “Mount Sharp” may have been formed.


      1. There’s a scale/resolution element. How many image pixels do those objects cover? We now have some marks visible covering over 100 metres. Compare that to something 5m across. There will be an error-bar for the on-ground measurement, but they have a lot more pixels to count. HiRise is usually quoted at 0.3 metres per pixel. Curiosity is 2.9 metres long by 2,7 metres wide, 9 or 10 pixels.
        OK, if the pixel count doesn’t match the movement info from the rover, there’s some explaining to do. But it’s a more precise measurement, and it doesn’t depend on analysing stereo pairs. The sources or error will be different.


        1. And NASA has had precisely the same ability since MRO arrived in orbit :). I’m not disputing what you say – rather that it’s nothing new. MRO has been tracking the movements of Spirit (up until the loss of that rover) and Opportunity (which resumed driving around Endeavour Crater in May) since it arrived in orbit. The MERs, while stationary, together with their landing platforms and the 2008 Mars Phoenix lander) have additionally formed static man-made targets of known size with which to assist in the characterisastion of HiRISE functionality.


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