Got questions about Curiosity? I've got answers for you
Posted by Emily Lakdawalla
19-07-2012 14:35 CDT
A few days ago, JPL and NASA released their media press kit for the landing of the Curiosity rover on Mars. (It's a PDF, 5.5 MB.) A press kit is a document designed to provide the media with answers to all of the basic -- and many not-so-basic -- questions they may have about what a spacecraft is, what it does, what it's made of, who made it, who runs it, why it's going to Mars, when major events can be expected to take place, what it might find, what it probably won't find, how it fits in with past and future Mars missions....hopefully you get the picture: it's packed with facts.
And while it's called a press kit, it's not just for the press; even if you're not a member of the media, you can read it, too. In fact, if you've ever asked yourself any question about the Curiosity mission -- and I hope that includes every single person reading this blog, whether you're a space fan or a scientist -- you should read the press kit. Googling for answers to specific questions is fine. You can ask me questions, too, which a lot of people do, but you'll answer your question faster by reading the press kit. What's more, you'll learn a lot of answers to questions you didn't know to ask. If you already know a lot about the mission, you'll learn how to talk about it in ways that make sense to people who don't know a lot about it.
I'm reading the press kit right now and am learning a lot of stuff I didn't know before, and being reminded of answers to frequently asked questions. For instance:
- When NASA says that the rover is landing at 10:31 p.m. August 5 PDT, they are talking about Earth Received Time -- that is, the time when a signal that landing has occurred will be received on Earth.
- The landing site is located at 4.6 degrees South latitude, 137.4 degrees East longitude.
- The call for proposals for instruments went out only three months after Spirit and Opportunity landed; the instruments were selected just eight months after that.
- The telephoto Mastcam 100 instrument could tell a football from a basketball at a distance of more than 600 meters.
- To take a full-color, 360-degree panorama with the medium-range Mastcam 34 instrument requires 150 images; their acquisition takes 25 minutes.
- Both of those can take 720p high-definition video at 4 to 7 frames per second.
- Magnets built in to the camera calibration target will repel martian dust, preventing it from accumulating on the color chips. (They're protected with a force field! Cool!)
- ChemCam can "quickly and unambiguously identify water if any is on the surface in the area Curiosity explores," presumably in the form of frost or bound into minerals.
- The Alpha Particle X-Ray Spectrometer depends upon a radioactive source, the synthetic element curium-244. It has a half-life of 18.1 years, more than twice as long as Opportunity (which, like Sojourner and Spirit, also had APXS instruments) has been on Mars.
- But Curiosity's APXS has, for the first time, a solid-state electronic cooler, so it can be used in the daytime, not just at night.
- Not only that, it has an autonomous placement mode: it can sweep along soil until it finds a good spot for measurement. This is unbelievably awesome.
- The MAHLI (hand-lens imager) is an enormous improvement over the previous microscopic imager. I'll write a lot more about this in a future post, but key features include adjustable focus and LED lighting. It's not just for imaging rocks and soils; it'll also take time-lapse video of moving parts of the rover like wheels and sample doors, and can do rover self-portraits.
- CheMin is an X-Ray Diffraction instrument for definitive identification of minerals making up more than 3% of any powdered sample. Its 32 sample cells include 5 reference samples and 27 reusable holders for Martian samples. One analysis takes up to 10 hours. Its detector is cooled to minus 60 degrees Celsius. Its X-ray fluorescence mode can identify elements with atomic number higher than 11 (sodium).
- CheMin's development began in 1989; spinoff technology is already in use in the form of portable X-ray chemical analyzers for screening for counterfeit pharmaceuticals in developing nations (I'll note editorially here that this is a very serious public health problem, especially for contagious incurable epidemic diseases like HIV that require lots of expensive pharmaceuticals). Who says space tech is of no use to the poor?
- The SAM instrument, occupying a box within the front end of the rover, contains 600 meters of wiring.
- SAM's tunable laser spectrometer can measure isotopic ratios in methane (if it's found), carbon dioxide, and water vapor.
- SAM has 74 0.78-cubic-centimeter sample cups. Of these, 59 are reusable quartz cups for high-temperature heating of samples; six hold calibration targets; nine contain liquids for a solvent-based method of organic chemical analysis. These nine cups are non-reusable.
- The weather station, REMS, can measure wind speed, wind direction, air pressure, relative humidity, air temperature, ground temperature, and ultraviolet radiation. Its detectors are located in places all over the rover mast and deck.
- The DAN instrument can detect the abundance of hydrogen within the ground to a depth of 50 centimeters beneath the rover. DAN will be used along traverses (in pauses between drives) and while the rover is parked.
- MARDI will take a video, yes, a video of Curiosity's descent to the surface at 4 frames per second. A few full-resolution frames will be among the first things transmitted to Earth, to allow JPL to pinpoint the landing location. A thumbnail version of this video will be available within a few days after landing. It might take some time for the entire full-resolution video to be transmitted to Earth. I'll write more about MARDI in a future post.
- Each of these science instruments has a principal investigator. Not a single one of them is a woman. Two of the three camera investigations -- Mastcam and MARDI -- are led by the same principal investigator (Mike Malin). The other P.I.'s are Ken Edgett (MAHLI), Roger Wiens (ChemCam), Ralf Gellert (APXS), David Blake (CheMin), Paul Mahaffy (SAM), Javier Gómez-Elvira (REMS), and Don Hassler (RAD). They are led by project scientist John Grotzinger.
- The rover's top speed is 4 centimeters per second, but that's only achieved while driving blind (that is, while executing commands from Earth like "drive forward for 17 wheel rotations"). When it's using autonomous control and hazard avoidance, the top speed is 2 centimeters per second.
- Curiosity has two complete main computers, an "A" side and a "B" side, for redundancy. Certain crucial tools, like the navcams, have redundancy within each side. There are also two pairs of Navcams. The top pair is connected to the A side computer, while the bottom pair (5 centimeters lower than the top pair) is connected to the B side computer.
- If one computer resets during landing, there is a software feature called "second chance" that allows the other side "to promptly take control, and in most cases, finish the landing with a bare-bones version of entry, descent, and landing instructions."
- The Hazcams have lens caps that will be removed using pyros after landing. The Navcams are protected during landing by being pressed against the deck with the mast in its stowed position.
And that's just a small selection of the information available in the press kit. So: I'm assigning it to you all as homework. If you're going to be watching Curiosity land, read this first! You never know when I might make you take a pop quiz!
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