by Michelle Evans for SpaceDaily.com
Los Angeles CA (SPX) Aug 02, 2012
"Ah, but a man's reach should exceed his grasp, or what's a heaven for?" Robert Browning asked in his 19th Century poem. This idea is what drives humankind to explore, to literally reach beyond and delve into what was once thought impossible. The very idea of people leaving the Earth, of walking on the Moon, and eventually Mars, is the literal essence of Browning's words. We must reach outward or we will grasp nothing.
The robotic arm on the Mars Science Laboratory definitely exceeds the grasp of a human. Curiosity's arm has a reach more than twice as far as a human's, registering nearly seven feet in length, not to mention being millions of miles away on another planet. All of the probes to successfully land on Mars have had some sort of robotic arm, all the way back to when the first Viking missions touched down in July and September 1976. Matthew Robinson is the Lead Robotic Arm Rover Planner and Systems Engineer for MSL. He explained how Curiosity's arm is literally the Swiss Army Knife of robotic arms.
"I was joking with my wife that I grew up in the 1980s watching MacGyver, and even MacGyver would be proud about [this arm]. The reason we've got so many tools is that when we get to Mars, we don't know quite what we're gonna find [so] we have to be flexible and creative with how we attack challenges."
Matt talked of the arm's capability, saying, "The robotic arm on MSL is by far the most complicated arm we have. It is about the same length as the Phoenix arm [which landed near the martian north pole in May 2008]. That arm had a soil temperature probe and a scoop, designed mostly like a backhoe to trench. This arm has a scoop, but it also has what we call CHIMRA [Collection and Handling for In-situ Martian Rock Analysis], which once we scoop up or drill a sample it has a number of internal sieves to separate a sample; we have a spectrometer; a camera which we call MAHLI [Mars Hand Lens Imager], which is a hand-held camera and is the nicest camera we've had on an arm before; and a Dust Removal Tool [with the appropriate acronym of DRT] so we can remove layers and years of sediment."
Another addition is the PADS, or Powder Acquisition Drill System. It is actually a miniature jack hammer which can power its way up to two inches inside a rock sample with a hole nearly 5/8ths-inch in diameter. I asked if this mechanism could actually break open Mars rocks.
Matt replied, "Possibly, depending on the hardness of the rock. We're not standing right there and we can't look at it. It's very easy for you or I to look at that and say, 'It looks like a a very hard, solid rock.' How does a robotic arm on our rover know? We have to have a bag of tricks for doing this and one would be a percussive test. We'll take the arm and push on the rock, apply a certain pre-load, then we'll do a kind of hardness test by tapping the rock a couple of times. It's possible, if it's not a very solid rock, it could fracture. That'll tell us that's not a rock we want to push on really hard... It's one of the challenges to train scientists and engineers to see through the eyes of a rover, and to use the robotic arm on the rover as an extension of [their] arm."
Without the arm, most of the science expected from Curiosity would be impossible. "To give you a sense of the scale of challenges," Matt said, "the rock arm has to be strong enough where you can lift a fifth-grader [more than 70 pounds] in order to apply the pre-load... But then it also has to be accurate enough where you can drop an aspirin into a thimble. Even though this arm is huge, the actual size of the sample we acquire is about the size of an aspirin... that's the level of powder we deliver to our science instruments. It's quite a complicated arm. In terms of mass, the cable alone for our robotic arm is more massive than the entire Phoenix arm, [even though] they're about the same length."
Interestingly, once on Mars, the two main tasks of MSL will be controlled by two Matts: Matt Robinson for the robotic arm and Matt Heverly in charge of driving the rover across the surface. Both of them, along with most of the science and engineering team, will literally be divorced from Earth as they are consumed by their job.
Matt Heverly explained what they will be going through. "The hard part about this is we work on the Mars day during the mission, so I come to work at 6:00 pm Mars Time, whatever time it happens to be on Earth. The Mars day is forty minutes longer than the Earth day so one day I show up to work at 9:00 am, and the next day I show up at 9:40, then 10:20. Every day we march along forty minutes later until I'm coming into work at 3:00 am. So our bodies and our lives have to adjust to Mars."
Neither Matt has a problem with "living" on Mars for the foreseeable future, since the basic mission is slated to hopefully last at least one martian year, equating to twenty-three months on Earth. Matt Robinson talked of what is ahead for them if everything goes as planned with the landing.
"The one thing we know is we've got to be flexible. We don't know exactly what kind of terrain we're going to land on. We have a decent idea, but we don't know if we'll be right up next to a target we'll be interested in scientifically, or if it's going to be hundreds of kilometers away. So it might be more of Matt [Heverly's] job to drive for a week or two before my job takes over, or be more for me to take over early, and we'll drive later... Once it lands on Mars, there's no 'on and off' switch for the rover. We're going to run this thing until the wheels fall off, so to speak. As far as my part in it, I'll be happy to do it as long as the rover is still alive and running.
Mike Watkins is the Mars Science Lab Mission Manager, meaning he oversees everything to do with design, navigation, and operations. He spoke of the primary difference between the way MSL is designed to function versus the landing missions which have preceded it. "I think one of the big things which differs from previous missions is that we're in for the long haul. We've designed a mission to take a couple of years to get the full science return.
"On this mission, landing's not good enough. We have to land, then we have to drive to the good stuff, and we have to sample the good stuff. And the notion this will take a couple of years, that we're in for a long expedition, not just a quick in and out, I think is something which is going to change planetary exploration. I think it's our realization that you really need to invest time, and we need to invest in significant missions to get new return. We need to have these longer-term missions, and I think that's what you're going to see."
Robinson agrees with Watkins, saying, "I think once this rover lands on Mars, and we see what its capabilities are, we're going to have to go back again... Working on a project like this, I think of it more as a lifestyle rather than as a profession. No one does this job just for a paycheck. It's a passion."
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