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Headshot of Emily Lakdawalla

Got questions about Curiosity? I've got answers for you

Posted by Emily Lakdawalla

19-07-2012 14:35 CDT

Topics: explaining technology, Curiosity (Mars Science Laboratory)

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!

Curiosity touchdown!


Curiosity touchdown!
In this scene, Curiosity has touched down onto the surface. The spacecraft has detected the touchdown, and pyrotechnic cutters have severed the connections between the rover and the spacecraft's descent stage.
See other posts from July 2012


Or read more blog entries about: explaining technology, Curiosity (Mars Science Laboratory)


Doppler: 07/19/2012 06:57 CDT

Are you giving odds on successful landing?

bware: 07/19/2012 10:06 CDT

Odds? Not calculated -- WAG -- I'll give 30% and that's because I want MSL to land safely. The SkyCrane is why I give it a 70% chance of failure. I do want MSL to succeed, I just fear it won't because of the SkyCrane. Then the partial flyaway ending in a CAB. Shrapanel and blast wave ...

planet4589: 07/19/2012 11:12 CDT

Hey Emily - well since you are offering, here's one Guy couldn't answer for me last year (and I see they still didn't fix the "3893 kg launch mass" typo I pointed out) - I still haven't seen a consistent mass breakdown for the descent vehicle - I have / Descent stage 829 kg dry, prop 387 kg, heat shield 385 kg, backshell 349 kg, 6 EMBD weights 150 kg, 2 CMBD weights 150 kg, which leaves 151 kg missing of 2401 kg total./ Just a heads up to be on the lookout for better numbers for these components as you come across other documents...

Doppler: 07/20/2012 05:51 CDT

I'm not a space pro, just a 57-year close observer of all things space... I'll see your 30% and raise you to even odds. Recent track record good, but lots of moving parts on lots of brand new tech. And as we are always reminded, Mars is a tough place.

fthurber: 07/20/2012 12:18 CDT

Does the rover have the ability to remove dust from its instruments, in particular the cameras? We all remember what happened to Mini-TES, alas?

fthurber: 07/20/2012 12:33 CDT

Hey Doppler, I would give odd of 70-80%. I say this since EDL is such a huge part of this project and they have an experienced, talented team. I would feel better if they did not use the sky crane and just powered down all the way (with proper protection of the instruments). Contrast this with the Beagle "landing". Before the landing, Colin Pillinger spent a lot of time discussing the capability of the lander, but EDL seemed like an afterthought to him. Ooops.

Zorbonian: 07/20/2012 03:39 CDT

If this is successful, it will definitely be a "moon landing" moment.

fthurber: 07/21/2012 07:25 CDT

The more I read about MSL the more my head spins. It has so many systems with so many options. It is inconceivable that all these systems will work exactly as planed and work perfectly in concert with each other. I just hope that the press does not focus on one tiny malfunction instead of the good stuff that does work. We are seeing this already with the whining about florocarbons on the drill bits. Huffington Post ran an article on all the Mars failures and how risky MLS is; it is almost as if they want it to fail.

ToSeek: 07/21/2012 09:52 CDT

Okay, so Curiosity has a death ray AND a force field. Now all it needs is a transporter beam!

bware: 07/21/2012 10:04 CDT

... and a name change to Enterprise. She'll need the reputation preceding her to ensure a safe landing!

fthurber: 07/22/2012 10:45 CDT

Is there a post landing schedule of events on MSL? What events of interest will happen in the hours after touchdown? I will watching at 1:31 A.M. here on the East Coast and was wondering how much longer we will have to wait to hear the status of the rover. How long until the first (MARDI?) images come down?

fthurber: 07/22/2012 11:06 CDT

I have been reading the 61 page press brief (I am pretty sure that Emily and I will be the only members of the press to do this!) and found a possible error about the APXS. Here it is: "... the specific isotope used in all Mars rovers’ APXS instruments is curium 244, which has a half-life of 18.1 years. this makes it ideal for long-duration missions, where even after more than seven years of the Opportunity mission, the loss in activity is hardly noticeable." I thought that Opportunity's APXS's required much longer integrations now....

fthurber: 07/22/2012 11:12 CDT

As we all know, Earth has received a small trickle of Mars samples via rocks blasted off Mars' surface by meteorite strikes and an subsequent SNC meteorite falls on Earth..... As of August 6, we can be assured that at least one Earth rock has reached Mars; the APXS instrument has a piece of terrestrial basaltic rock slab for calibration!

Dusty: 07/22/2012 09:27 CDT

The press briefing said Mars has 1/10th the mass of earth. Why is gravity on Mars 38% of earth rather than 10%?

Dave: 07/23/2012 08:19 CDT

Dusty, The reason is the diameter of Mars is less than earth. The equation for force from gravity is F = G*m1*m2/r2... where r is the distance between the centers of mass. Sitting on the surface of mars you are closer to the center of the planet.

Jaro: 07/25/2012 04:51 CDT

I see there is no Mossbauer gamma spectrometer on Curiosity: Is its function entirely replaced by the CheMin X-Ray Diffraction instrument ? According to the Press Kit, "Each CheMin analysis of a sample requires up to 10 hours of accumulating data while the X-rays are hitting the sample." ....that seems awfully long ! ....about the same as when the MER's Mossbauer Co-57 sources became depleted. What are the pros & cons of each type of instrument ? How are they complemented by the Alpha Particle X-Ray Spectrometer (APXS) ? PS. I agree with a previous post pointing out how unbelievably awkward it is to post a comment on here.... PLEASE do something about it !!!

fthurber: 07/31/2012 09:23 CDT

There are some other interesting MSL videos out there besides the viral 7 Minutes of Terror. Here is a more comprehensive video about the rover instruments. The fun thing is that the narrator sounds like Dr. Carol Marcus describing the Genesis project in Star Trek: The Wrath of Khan. I am not sure if this was done intentionally by JPL but it is very entertaining to watch: There is a really great video about the geology of the landing site by Matt Golombek. Golombek is fantastic:

fthurber: 07/31/2012 09:41 CDT

The big problem I see with MSL (and MER) is a design flaw in its mobility system. The problem is the wheels. I have done some driving on loose sand beaches on Cape Cod, and the important thing is to have huge, smooth, soft tires. Some drivers will actually let air out of their tires before driving on the beach. MSL and MER have the opposite or what you want: small, hard, knobby wheels. We already saw the disastrous results with Spirit and and almost disastrous results with Opportunity. And MSL will face a line of sand dunes between its landing site and the clay layers at the base of Mt. Sharp; yikes.

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