Know your rover: Curiosity

What are the instruments that adorn NASA's Curiosity rover?

An artist's depiction of the Curiosity rover, currently on Mars (Image from Wikimedia Commons)

During an interview on November 20 with NPR’s Joe Palca, the Curiosity mission’s chief investigator John Grotzinger mentioned something the rover has found that’s “one for the history books”.

Given this development: Here is a short breakdown of the instruments on the car-sized Martian rover, and what each accomplishes.

1. Sample Analysis at Mars (SAM) - SAM’s in place >to look for carbon dioxide and methane in the Martian soil and atmosphere. It uses three instruments, including the Tunable Laser Spectrometer (TLS), to distinguish between the sources of the compounds, i.e., if they’re of geochemical or biological origins.

2. Dynamic Albedo of Neutrons (DAN) – DAN does for hydrogen, water, and ice what SAM does for carbon dioxide and methane. It uses neutrons to “read” samples from the soil and a detector to analyse the results.

3. Chemistry & Mineralogy (CheMin) – The CheMin instrument is basically an X-ray diffraction installation. The rover drills into Martian rock, and the fine powder it gets is poured into a tube, at which a beam of X-rays is shot. The rays are deflected at different angles for different minerals in the sample, and measuring them gives an idea as to >the composition of Martian soil .

4. Radiation assessment detector (RAD) – If you know the RAD’s been turned on, you know Curiosity’s doing a check on the kinds of radiation in the Martian atmosphere. Interestingly RAD also kicked in during the rover’s cruise phase before landing, throwing light on the kinds of radiation shields humans would’ve to be equipped with if they wanted to visit the red planet.

5. Mars Hand Lens Imager (MAHLI) – A camera on the rover’s robotic arm, MAHLI is capable of snapping microscopic pictures of Martian soil. It’s equipped with visible-light, ultraviolet and fluorescence imaging modules, and comes with a resolution of 1600 x 1200 px (at 1.43 μm per pixel).

6. Alpha-particle X-ray spectrometer (APXS) – When a target is irradiated with alpha-particles – each basically two protons and two neutrons in a bundle – it emits X-rays at different frequencies (a process called >PIXE ). Each frequency corresponds to an element, and so the APXS works similarly to the CheMin.

7. Hazard Avoidance Cameras (Hazcams) – When you’re watching a movie in 3D, you’ve got special glasses on that are simply color-filters. The technique itself, which gives rise to a sensation of depth by filtering certain frequencies of light, is called stereoscopy. The four stereoscoping Hazcams on Curiosity are positioned like eyes on its head: two at the front and two at the back. They sweep a range of 120° and a distance of 3 m, and allow the Earthbound crew to help the rover avoid obstacles.

8. Navigation cameras (Navcams) – On Curiosity’s mast are four black-and-white cameras that sweep a 45° arc to assist with navigation. The Hazcams and the Navcams work in tandem with a local software that helps the rover make its own navigational choices. The images are stored in the ICER format, which is similar to the >JPEG2000 compression protocol.

9. Rover Environmental Monitoring System (REMS) – This is Curiosity’s in-built weather-station. It measures humidity, pressure, temperature, wind-speeds, and ultraviolet radiation in the rover’s vicinity.

10. Chemistry and Camera complex (ChemCam) – As the name indicates, this device is not one part but two. The Remote Micro Imager (RMI) provides high-resolution images of rocks and soil up to 7 m away to scientists at NASA. The laser-induced breakdown spectroscopy (LIBS) vaporizes small amounts of the imaged rock with 50-75 5-nanosecond pulses of infrared radiation (λ = 1067 nm), then sits back and observes the radiation emitted from the sample.

11. Mast Camera (MastCam) – Basically a camera module with a kickass resolution, the MastCam is composed of the Medium Angle Camera (MAC), which sweeps 15° and yields 22 cm/px at 1 km, and the Narrow Angle Camera (NAC), which sweeps 5.1° and yields 7.4 cm/px at 1 km.

12. Mars Descent Imager (MARDI) – As with all other cameras on Curiosity, the specifications are: 90° sweep, 1600 x 1200 px, 1.5 m/px at 2 km, 1.5 mm/px at 2 m, 8 GB internal buffer memory.

While these instruments execute the vision of terran scientists, what’s to execute their will? This is the task of the robotic arm, a 2.1-m long feat of engineering that comes with a cross-shaped turret with slots for five devices, and a sweep of 350°. It weights 30 kg when mounted with all tools, measures 60 cm in diameter, and has three joints to assist with its manoeuvres.

So, you’re now in a position to step wide of the influence of factual inaccuracies – the more carelessly made ones anyway – and know what the rover’s actually up to if you see names like MARDI, MAHLI, SAM, and DAN in the papers.