OK, *one* more Curiosity descent video

By Phil Plait | August 28, 2012 11:25 am

I know, I’ve posted a few of these, but a new video came out showing the descent of Curiosity to the surface of Mars that’s worth a look.

YouTube user "hahahaspam" did a clever thing. The Mars Descent Imager (MARDI) is a camera that points straight down, past the rover, so engineers on Earth could later see the exact path Curiosity took on its way down to the Martian surface and also get an overview of the area. It took a series of images that were later put together to make various animations (see Related Posts below). The motion appears jerky because the camera only took about four pictures per second.

What hahahaspam did was interpolate between the frames, making the motion appear much more smooth. The animation he made is really quite wonderful:

Nice, huh? Interpolation is a math term that involves estimating the value of something between two measurements. A simple example involves someone running. You measure their progress: after one second they’ve traveled 2 meters, and after two seconds they’ve run 4 meters. How far did they get in 1.5 seconds?

Obviously, the answer is 3 meters. It may not be exact – a person’s running speed might change – but it’s probably close. There is a precise mathematical way to do interpolations like this, and that’s what hahahaspam did. Digital pictures are really just long strings of numbers, and video is the same thing except each pixel value changes with time. All you need to do is take two frames taken some time apart, then interpolate the value at each pixel for what it would be halfway between the time of the first frame and the second, and boom! You’ve made a video with twice the frame rate and the motion looks smoother.

It’s actually a lot harder than this in practice (rapid brightness or color changes makes this more difficult and less accurate, for example), but I hope this gives you the idea of how it works. The result in this case is pretty cool. Hahahaspam also created a side-by-side comparison of the original and interpolated videos, too, so you can see how they look together.

Very nice! And well done. I think it’s great that so many folks are so inspired by this that they want to play with the data. It really shows how much this has affected people.

Related Posts:

Two amazing Curiosity descent videos
Watch as Curiosity touches down gently *and* its heat shield slams into Mars
Video of Curiosity saying bye bye to its heat shield
VIDEO of Curiosity’s descent… from the rover cam itself!

CATEGORIZED UNDER: Cool stuff, NASA, Pretty pictures

Comments (19)

  1. dirk

    Where can I find a similar video of one of the moon landings? Maybe a computer sim showing how the orbiter & eagle interacted in landing and launch. I know something like that must exist, but Google let me down.

  2. Grimoire

    I didn’t see the side by side version before. Very nice indeed!

  3. Nice.

    And I just had the opportunity to explain “extrapolate” to my daughter yesterday, with this picture from George Takei:


  4. Very clever! And a great result.
    Thanks hahahaspam.

  5. That’s a wonderful enhancement of the original, but *heh* the viewpoint rotates about 270 degrees during the descent – I wonder how hard it would be to de-rotate the viewpoint so ‘up’ is constant…

  6. What was done here is (apparently) a lot fancier than interpolating the pixel values; that would mean simply fading from one frame to the next, and you’d see double images most of the time. This interpolation first had to compare the viewing angles of adjacent frames and transform both views to an intermediate view before blending.

    By the way — Near the beginning there’s a bright spot near the top of frame. I wonder, is that simply a very pale patch of sand, or a reflection of the sun?

  7. That bright spot is the point opposite the Sun where light is scattered back towards the observer – I forget the proper name, it’s related to the ‘brockengeist’ halo you see looking down from a mountaintop onto mist below

  8. The music is also interpolated, from various sounds…

    Oh, wait. This isn’t Fake Science. This is Bad Astronomy.

  9. Gustav

    I don’t mind one bit Phil, not one bit.

  10. AndresMinas

    I wish they’d put the altitude, time and speed of the descent below or at any side bar of the video. In the last 3 seconds (before the dusting), I thought I am still at 1000 meter above the ground looking at some of those Mars valley craters!

  11. Buzz Parsec

    Dirk @ 1,

    I doubt the raw material for that exists or ever existed. There was no such thing as digital video in 1969; you would have to digitize film or analog TV. There was no TV camera in the LM the one they used during the moon walks was deployed from the side of the descent stage as Neil Armstrong climbed down the ladder. (It was upside down, and NASA had to flip the image over. For the first few seconds, it went out over the TV networks upside down, but then someone flipped a switch to invert it. Once one of the astronauts retrieved it, they had to turn the image back upside-up. ) And it was all in black & white.

    The footage you see out the window of the dust kicking up as they landed was taken with a film camera (16mm, I think) and there was only a few minutes of film at most.

    Later landings had color video cameras, and I think they used them to record the launch from the moon, from both the outside (under remote control) and at least a few times from inside the cabin. People have produced cleaned-up versions of these videos, but they are intrinsically much lower resolution than Curiosity’s cameras.

  12. Felix

    That’s really fantastic – so much easier to watch and notice details.
    For example is the dark land at the start the mountain range that Curiosity will be exploring?

    Great music too!

  13. Anthony

    Unless he was working from someone else’s video, there’s also a fair amount of color and contrast enhancement going on there..

  14. VinceRN

    Wow, nice. So far I can’t get enough of these, so keep it up if you find more.

  15. I like the way it’s easier to spot the moments when the parachute detaches, the back protective whatchamacallit is blasted off, and the skycrane’s motors kick in. Everything suddenly gets very stable. And then when the skycrane itself starts to lower the lander, the rotation suddenly stops and you go straight down.

    Nifty nifty nifty.

  16. Peter B

    Dirk @ #1: This video might go some of the way: http://www.youtube.com/watch?v=G9Nh5qWzqMY&hd=1 It compares the Apollo 11 descent video with an image of the Apollo 11 landing site by the Lunar Reconaissance Orbiter.

    Otherwise, I don’t think what you’re after exists. Perhaps you could develop it yourself?

  17. Matt B.

    Dang, I keep reading it as hahahaspasm.

    Anyway, It occurs to me that maybe they should have put the camera on the bottom of the sky crane. Then we could have seen the rover dangling there, and seen it rush away after the crane disconnected.


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