You Say Blue, I Say Cerulean (zocalopublicsquare.org)

Interesting this comes up now, there was a talk at my lab a couple of days ago by Jim Bell of ASU - he is/was responsible for the Pancam payload on MER, i.e. the main stereo cameras. The talk was about colour calibration used on these rovers.

Essentially as Spirit and Opportunity were only designed for a 90 day jaunt, the calibration target wasn't designed to be in use for very long. Over 3000 days later it's covered in dust. However, there's also a white/grey patch that has a ring magnet underneath it. The centre of the magnet is totally clear of dust (which is largely magnetic, lots of Iron on Mars), and is pretty much the cleanest part of the rover as a result. Turns out it's quite useful because as more dust accumulates, we can better simulate the Martian atmosphere. You can see the magnet in the top right, note the centre is still white!

http://www.hour25online.com/pix/Spirit_dust-comparison_feb05...

MSL Curiosity uses the flight spare from the MER project. It's the thing that looks a bit like a joystick.

https://planetary.s3.amazonaws.com/assets/images/z_changeove...

The six rings on the surface are where the new 'sweep' magnets are, you can see some small debris has gotten stuck to them. It looks like they upgraded it a bit and put them on all the colour targets.

This approach is also used for other sensors onboard (UV photodiodes in this case):

http://www.spaceflight101.com/uploads/6/4/0/6/6406961/977765...

A delightful article. I would also recomend this article:

http://www.wired.com/2012/06/the-crayola-fication-of-the-wor...

The crayola-fication of the world: How we gave colors names, and it messed with our brains, Aatish Bhatia, 6/5/12

It is a fascinating discussion of the origins of color words and how our perceptions are, well, colored by them. It also touches on the XKCD color map (search for "XCKD Color Survey Results"), another lovely insight into color names and perceptions.

The minute I've heard Cerulean all I can think of was Trillian instant messenger.

Perhaps a little off topic, but I wonder if the author knew that "Orchid" (alas, minus the subterranean) was indeed an obscure (and amazing) punk rock band?

I can't find the article but somewhere I read that a boy was intentionally never told what "color" the sky was. He could see color normally but when asked what color the sky was, he said "Clear."

I'm amused that the author chose a centuries old color name that's been in relatively frequent written use all that time for the title. The article centers on the history behind huge catalogs number of obscure color names, but he chose one that's not at all obscure. OTOH it's kind of a win because cerulean isn't the generic "blue" most people would think of, so it nicely illustrates the use of distinguishing color names.

Worth a mention of xkcd's color survey [1] results [2] with two different shades of cerulean.

[1] http://blog.xkcd.com/2010/05/03/color-survey-results/

[2]http://xkcd.com/color/rgb/