The Martian by Andy Weir

(New York: Ballantine Books, 2014), 385

This time around, I needed a reliable way to fix my position on Mars.

Latitude and longitude. That's the key. The first is easy. Ancient sailors on Earth figured that one out right away. Earth's 23.5-degree axis points at Polaris. Mars has a tilt of just over 25 degrees, so it's pointed at Deneb.

Making a sextant isn't hard. All you need is a tube to look through, a string, a weight, and something with degree markings. I made mine in under an hour.
So I go out every night with a homemade sextant and sight Deneb. It's kind of silly if you think about it. I'm in my space suit on Mars and I'm navigating with sixteenth-century tools. But hey, they work.

Longitude is a different matter. On Earth, the earliest way to work out longitude required them to know the exact time, then compare it to the sun's position in the sky. The hard part for them back then was inventing a clock that would work on a boat (pendulums don't work on boats). All the top scientific minds of the age worked on the problem.

Fortunately, I have accurate clocks. There are four computers in my immediate line of sight right now. And I have Phobos.

Because Phobos is ridiculously close to Mars, it orbits the planet in less than one Martian day. It travels west to east (unlike the sun and Deimos) and sets every eleven hours. And naturally, it moves in a very predictable pattern.

I spend thirteen hours every sol just sitting around while the solar panels charge the batteries. Phobos is guaranteed to set at least once during that time. I note the time when it does. Then I plug it into a nasty formula I worked out and I know my longitude.

So working out longitude requires Phobos to set, and working out latitude requires it to be night so I can sight Deneb. It's not a very fast system. But I only need it once a day. I work out my location when I'm parked, and account for it in the next day's travel.

It's kind of a successive approximation thing. So far, I think it's been working. But who knows? I can see it now: me holding a map; scratching my head, trying to figure out how I ended up on Venus.

Morse Code (289)

To save time, Mindy had taught herself Morse code, so she wouldn't have to look each letter up every morning. She opened an e-mail and addressed it to the ever-growing list of people who wanted Watney's daily status message.

Topic: Science Fiction, Kid's Books

Source

SpaceX 2015

Created: 2025-10-11-Sat
Updated: 2025-11-14-Fri