Everyone’s talking about the $2.5 billion Curiosity rover‘s “terrifying” Hollywood-blockbuster-worthy landing: seven knuckle-in-teeth minutes in early August during which its aeroshell-armored bulk will plummet through Mars’ thin atmosphere at incredible speeds, snap apart to shed its back-shell, then fire rockets to slow its descent. It’ll be like Iron Man pulling out of a planetary dive, finally hovering dozens of feet above the designated Martian landing site — Gale Crater, near an 18,000-foot tall mound of debris — to gently lower the Mini-Cooper-sized rover itself from a nylon tether.
That’s the story you’ll see grabbing eyeballs as we roll toward touchdown on August 6, 2012 — and with good reason, given the landing’s almost mad-sounding chain of must-occur-exactly-so events.
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But what happens once the rover’s safely on the ground and NASA’s popping champagne corks? Assuming Curiosity — aka the Mars Science Laboratory, or MSL — survives the journey, what about the technology it’s hauled for over eight months through 354 million miles of vacuum at close to 48,000 miles per hour, and that it’ll deploy during its nearly two-year exploratory mission?
To understand the tech, you have to first understand Curiosity’s purpose.
“If you had to reduce the MSL’s scientific mission to one word, it would be habitability,” says MSL deputy project scientist Dr. Ashwin Vasavada. “For better than a decade, we’ve been doing what we call ‘following the water.’”
Water is one of the common factors for all known life on Earth, and therefore at the crux of any investigative journey to understand whether Mars could have contained — or ever harbored — life itself.
“So now we’re asking the next question, which is not just water, but what about the other ingredients that life would require,” says Vasavada, noting that Curiosity has a much broader mission than prior rovers: looking for life sources like carbon, water, sunlight and chemical energy, as well as hazards to life in the form of radiation.
“We do this broad survey of the environmental conditions at our landing site to see if we can call anything we find a habitable environment,” he says.
Radiation Assessment Detector (RAD)
Speaking of radiation, Curiosity’s RAD — the first of 10 instruments turned on — was designed to analyze radiation from the Martian surface, but also in the confines of the spacecraft carrying the rover to Mars during its eight month journey, to help assess the impact of radiation on astronauts who might someday participate in a manned mission to the Red Planet.
“The RAD instrument is unique in that we’re carrying it on behalf of the Human Exploration & Operations branch of NASA,” says Vasavada. “We have nine scientific instruments that come from the scientific community with the goal of addressing human habitability on Mars, and then we have this one instrument, RAD, trying to understand what astronauts would have to deal with on the surface. It also plays well into our habitability investigation, because it measures the same radiation that would harm humans or any other microbial life. So it has a dual purpose.”
But the key point, says Vasavada, is that with RAD, we’ll be able to acquire data we’ve never had before: radiation levels on the journey from Earth to Mars, and at the surface of the planet itself.
Radioisotope Thermoelectric Generator (RTG)
Like the Apollo spacecraft and deep space vessels deployed to Jupiter and Saturn, Curiosity will sip power during its two-year mission from electricity produced by the heat from 32 marble-sized pellets containing plutonium-238 dioxide (think “nuclear battery”). That adds up to about 10 pounds, which is pretty substantial, whether you’re a consumer laptop or a multibillions interplanetary mobile science lab.
“We’re a big rover, and because of the science we’re doing, we have to carry these big laboratories and a huge arm to take samples,” says Vasavada. “Once you have a big enough rover, you can afford to carry around this RTG. If you mounted this on smaller rovers, like Spirit or Opportunity, they’d keel over. We have a big spacecraft that needs to last a long time, and so we could afford to attach this power source that we’ve used on many missions before to a rover for the first time.”
How much power are we talking? “Only 100 watts, so about like a light bulb,” says Vasavada, noting that that’s still better than the power generated by solar panels averaged over the entire day.
“We generate 100 watts, 24-and-a-half hours a day, and we store that in a big battery,” he says. “And when we actually run the rover, we do so for five or six hours during the daytime on Mars. We run off the stored energy, so it’s sort of like charging a cellphone.”
Heat Rejection System (HRS)
Curiosity will have to withstand temperatures that can range from a balmy 86 F to nearly -200 F. By comparison, the lowest recorded non-laboratory surface temperature on Earth to date was about -130 F (in Antarctica, no surprise). To maintain a more stable temperature range, Curiosity employs a thermal regulation system not unlike the liquid-based ones sometimes found at the core of over-clocked do-it-yourself computers.
“We use a fluid loop system inside the rover to transfer heat in both directions,” says Vasavada. “The problem is that we have to endure these huge temperature changes. Mars is basically like a desert in having ground that changes temperature drastically between day and night. So we use the fluid loop system to pump heat from the RTG into the electronics at night, when it’s cold. And then in the daytime when it’s hot, especially with all the electronics running, it’ll draw heat from them and radiate it out into the Mars environment.”
And everything has to be designed perfectly, too, including the packaging, say the way one piece of material is glued to another — material which Vasavada says can expand and contract at different rates. Get this wrong, and pieces could eventually peel apart or break.
Rover Compute Element (RCE)
Curiosity employs two computers, one for daily operation and one for backup, each packing a 200 MHz IBM RAD750 (based on IBM’s late 1990s 32-bit PowerPC processors), 256 MB of RAM, 2GB of flash storage and running a multitasking operating system called VxWorks (used in multiple other spacecraft, including both Spirit and Opportunity rovers).
“All of our electronics have to be built in a way that allows them to withstand the environmental conditions,” says Vasavada. “So in addition to the temperature, there’s the extremely dry Martian air, where we have to address concerns about electrical arcing, for instance.”
But the biggest thing separating computing equipment designed for use on Mars from its consumer-grade counterparts on Earth is its resistance to radiation.
“Within Earth’s atmosphere we’re protected from a lot of cosmic rays and solar particles that would cause problems with electronics,” says Vasavada. “But on Mars, as well as on the way to Mars, you’re constantly bombarded by cosmic rays.”
The problem, especially with modern computing equipment, is that a single cosmic ray can flip the bit of a particular circuit, explains Vasavada. That can introduce software errors, causing things to fault or execute incorrectly.
“All of Curiosity’s electronics are built with fault protection, so they’re always double- or even triple-checking themselves, sending multiple signals and ensuring they match,” he says. “And the computing equipment itself is commercial grade, but in a special radiation-hardened configuration.”
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The true color, high-definition cameras
What fun is trundling around another planet with cutting-edge rovers if they can’t grab lovely images of it? To that end, Curiosity wields a variety of cameras, including two capable of capturing images at 1600 x 1200 pixels as well as high-definition video at 720p and up to 10 frames per second — specs unprecedented for a rover mission.
“You can think about the Curiosity’s camera system in two ways,” says Vasavada. “In one sense, they’re all a generation or two behind what’s available at Best Buy, because of how we go about qualifying equipment to work in space, but on the other hand, from the Mars perspective, they’re the best cameras we’ve ever flown.”
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Take color, for instance, which all prior Mars cameras have lacked, instead snapping unflattering grayscale pictures and requiring RGB filters to build up a color image — a process that requires three times as many images.
“Now we employ what are called Bayer filters, which are exactly what’s now on all consumer cameras,” says Vasavada, referring to the micro-RGB filters located on a camera’s detection technology itself. “Every time you take a picture, you’re taking a color picture inherently.”
But where the original proposal for Curiosity’s camera system was very ambitious, one of the coolest-sounding features didn’t make the final cut.
“We were originally looking at 15-to-1 optical zoom cameras, both a left and right stereo pair,” says Vasavada, referring to the camera system that at one point had filmmaker James Cameron’s attention. Unfortunately it was a little too ambitious. For instance, Vasavada says the system would have had to fit inside something as small as a lipstick tube.
“About halfway through, we decided to cut our losses and keep all the other capabilities,” says Vasavada. “And we did something interesting, which is that we decided not to have matched left and right cameras.”
NASA loves its panoramic shots, like the latest head-turner recently assembled from a whopping 817 images snapped by the Opportunity rover. Zoom capability would have allowed NASA to zoom out and snap just four or five pictures to assemble a panorama, or, alternately, zoom in to take a high-res panorama of something like a rock in the distance.
“We decided, when we got rid of the zoom capability, to leave just one of the cameras as a kind of telephoto lens, and the other cameras as a medium angle lens. So we have one camera that takes about a three times higher resolution image than the other camera, and they’re both capable of color and high-definition resolution.”
The radio communications system
Curiosity has two ways to talk to us on Earth: a high-gain X-band receiver (Vasavada says it resembles a giant lollipop) that can chat direct with Earth with distance-related delay times of just under 14 minutes, and a UHF radio that can talk to the spacecraft currently orbiting Mars, operating as relay stations.
“Both have their advantages and disadvantages,” says Vasavada. “The upside of talking direct is that you don’t have to rely on an Orbiter, which since it’s orbiting the planet, isn’t available at all times. The downside is that you have to aim it at Earth, so you have to first find the sun in the sky and reorient the Rover. But once you get that going, the direct antenna is the one we’ll use to upload a day’s worth of commands.”
Vasavada says there’s even a third way to talk to Curiosity in a pinch: a low-gain antenna that doesn’t have to be aimed, allowing the rover to simply signal that it’s there or receive rudimentary commands like “reboot.”
CheMin and SAM
“The primary way we look at ancient rocks on Mars to determine if they represent a habitable environment is to acquire samples of the rock with this big power drill that’s on the end of Curiosity’s robotic arm,” says Vasavada. “So we actually jackhammer into rocks, acquire the powder we’ve created and then deliver that powder to two core instruments that we call our laboratory instruments.”
One of those instruments is dubbed CheMin (for “Chemistry and Mineralogy”) and the other is called SAM (for “Sample Analysis at Mars”). Vasavada says these comprise Curiosity’s “core” laboratory capabilities.
CheMin uses technology called X-ray diffraction to shine an x-ray beam through the powdered rock and create diffraction patterns (“Basically like rainbows,” says Vasavada) allowing scientists to discern the rock’s mineral composition, which in turn helps build a much more thorough picture of the environment.
“This is the gold standard technique that’s used on Earth to identify minerals in any sample, and we’re bringing it to Mars for the first time,” says Vasavada.
And then there’s SAM, which includes both a mass spectrometer and a gas chromatograph, giving it CSI-like capabilities, according to Vasavada. Vasavada says SAM is “the biggest, most complex instrument Curiosity carries,” adding, “You could say it’s the one the entire rover was built around.”
When you deposit samples for analysis in SAM, for instance, the mass spectrometer can determine, element by element, what the chemistry of the sample is, while the gas chromatograph is used to separate different chemical compounds from each other and detect organic compounds that contain carbon.
“Organic compounds are where things get really interesting if we find them on Mars, because they could be used as building blocks of life,” says Vasaveda. “Or, and I don’t know if we’ll be able to tell this for sure, they could even be the remnants of life.”