We’ve seen them so often they no longer have any impact: Earth-rise taken by Apollo 8, the lift-off of Apollo 11, Aldrin on the Moon, anything taken by the Hubble Space Telescope. Well, I want to argue that the picture below is in the same class.
What’s so special about this picture? It’s a partial eclipse of the Sun. Big deal. But that’s not our Moon, that’s Mars’s moon Phobos, and the picture was taken by a spacecraft called Opportunity sitting on the surface of Mars. And so here’s just a few reasons why this is a very cool picture:
- Did you read that bit: “sitting on the surface of Mars”? That’s another planet. For most of our history, getting to the next hill was a major adventure.
- It shows we understand celestial mechanics. Eh? Well, that’s how the planets move: where they will be and when. For this picture we need to know where Mars, Phobos and the spacecraft are so we know when the shadow will cross the spacecraft. So that’s thanks to Newton, Kepler, Einstein and Co for getting the maths and physics sorted. In the Aztec empire if you could predict an eclipse you became a High Priest and could sacrifice virgins on demand – just think what power you’d get with predicting this shot!
- We’ve only had photography for less that two hundred years. The spacecraft has a digital camera to take the picture: Fox Talbot would blow a gasket. So we need to know about optics, materials, semiconductors and image processing.
- Developing the film. OK, so we’re not talking about taking a roll of 35mm film to the chemist 1 and picking up the pictures a week later. No, the spacecraft takes the picture and compresses it and sends it to an orbiting communications spacecraft that relays it to Earth where a big antenna hears the signal and sends it a big computer for processing. So we have advanced radio (bags of maths + physics), image compression (more maths), photo processing, and a shed-load of software in the spacecraft, antenna, network and control centres. I’m starting to drool, it’s so cool.
- Positioning the camera: we need to get the camera in place. It’s not just a matter of driving up a hill, setting up the tripod and clicking the camera on. Mars at its closest is 55 million km away so signals take at least 3 minutes to travel to Earth. So we need a big rocket, 6 months to get there, and a big brake to land softly on the surface. Not everyone lands softly: Beagle 2 made a nice crater. Yes, this is rocket science: lots of money, big brains and lots of luck are needed.
- Pressing the shutter. Since a 55 million km cable release is a little impractical we need something else to control the shutter. And yes, it’s a computer, running some software. But this is way cool software: designed to run when unexpected things happen. Software that allows a software engineer on another planet to update, debug, tweak and monitor it. Oh, and the computer has to survive a wide temperature range, handle nasty radiation, need almost no power, and be resilient. So forget the latest processors running Windows…
I rest my case.
- Younger readers can go back to playing with their mobile phones at this point. ↩