And I have to hustle. Dust storms move. Sitting still means I'll likely get overwhelmed. But which way do I go? It's no longer an issue of trying to be efficient. If I go the wrong way this time, I'll eat dust and die.

I don't have satellite imagery. I have no way of knowing the size or shape of the storm, or its heading. Man, I'd give anything for a 5-minute conversation with NASA. Now that I think of it, NASA must be shitting bricks watching this play out.

I'm on the clock. I have to figure out how to figure out what I need to know about the storm. And I have to do it now.

And right this second nothing comes to mind.

Mindy trudged to her computer. Today's shift began at 2:10pm. Her schedule matched Watney's every day. She slept when he slept. Watney simply slept at night on Mars, while Mindy had to drift 40 minutes forward every day, taping aluminum foil to her windows to get any sleep at all.

She brought up the most recent satellite images. She cocked an eyebrow. He had not broken camp yet. Usually he drove in the early morning, as soon as it was light enough to navigate. Then he capitalized on the midday sun to maximize recharging.

But today, he had not moved, and it was well past morning.

She checked around the rovers and bedroom for a message. She found it in the usual place (north of the campsite). Reading the Morse code, her eyes widened.

“DUST STORM. MAKING PLAN.”

Fumbling with her cell phone, she dialed Venkat's personal number.

Chapter 23

LOG ENTRY: SOL 476

I think I can work this out.

I'm on the very edge of a storm. I don't know its size or heading. But it's moving, and that's something I can take advantage of. I don't have to wander around exploring it. It'll come to me.

The storm is just dust in the air; it's not dangerous to the rovers. I can think of it as “Percent power loss.” I checked yesterdays power generation and it was 97% of optimal. So right now, it's a 3% storm.

I need to make progress and I need to regenerate oxygen. Those are my two main goals. I use 20% of my overall power to reclaim oxygen (when I stop for Air Days). If I end up in an 81% part of the storm, I'll be in real trouble. I'll run out of oxygen even if I dedicate all available power to it. That's the fatal scenario. But really, it's fatal much earlier than that. I need power to move or I'll be stranded until the storm passes or dissipates. That could be months. 

The more power I generate, the more I'll have for movement. With clear skies, I dedicate 80% of my total power toward movement. I get 90km per sol this way. So Right now, at 3% loss, I'm getting 3.3km less than I should.

It's ok to lose some driving distance per sol. I have plenty of time, but I can't let myself get too deep in the storm or I'll never be able to get out.

At the very least, I need to travel faster than the storm. If I can go faster, I can maneuver around it without being enveloped. I need to find out how fast it's moving.

I can do that by sitting here for a sol. I can compare tomorrow's wattage to today's. All I have to do is make sure to compare the same times of day. Then I'd know how fast the storm is moving, at least in terms of percent power loss. 

But I need to know the shape of the storm, too.

Dust storms are big. They can be thousands of kilometers across. So when I work my way around it, I'll need to know which way to go. I'll want to move perpendicular to the storm's movement, and in whatever direction has less storm.

So here's my plan:

Right now, I can go 86km (because I couldn't get a full battery yesterday). I'm going to leave a solar cell here and drive 40km due south. Then I'll drop off another solar cell and drive another 40km due south. I'll have three points of reference across 80km.

The next day, I'll go back to collect the cells and get the data. By comparing the wattage at the same time of day in those three locations, I'll learn the shape of the storm.  If the storm is thicker to the south, I'll go north to get around it. If it's thicker north, I'll go south.

I'm hoping to go south. Schiaparelli is southeast of me. Going north would add a lot of time to my total trip.

There's one slight problem with my plan: I don't have any way to “record” the wattage from an abandoned solar cell. I can easily track and log wattage with the rover computer, but I need something I can drop off and leave behind. I can't just take readings as I drive along. I need readings at the same time in different places.

So I'm going to spend today working on some mad science. I have to make something that can log wattage. Something I can leave behind with a single solar cell.

Since I'm stuck here for the day anyway, I'll leave the solar cells out. I may as well get a full battery out of it.

LOG ENTRY: SOL 477

It took all day yesterday and today, but I think I'm ready to measure this storm.

When I packed for this road trip, I made sure to bring all my kits and tools. Just in case I had to repair the rover en-route.

I made the bedroom in to a lab. I stacked my supply containers to form a rudimentary table, and used a sample box as a stool.

I needed a way to track the time of day and the wattage of the solar cell. The tricky part is logging it. And the solution is the extra EVA suit I brought along.

The cool thing about EVA suits is they have cameras recording everything they see. There's a camera on the right arm (or the left if the astronaut is left handed), and one above the faceplate. A time-stamp is burned in to the lower left corner of the image, just like the shaky home videos Dad used to take.

My electronics kit has several power meters. So I figure: why make my own logging system? I can just film the power meter all day long.

So that's what I set up.

First, I harvested the cameras from my spare EVA suit. I had to be careful; I didn't want to ruin the suit. It's my only spare. I had to get the cameras and the lines leading to their memory chips.

I put a power meter in to a small sample container, then glued a camera to the underside of the lid. When I sealed up the container, the camera was properly recording the readout of the power meter.

For testing, I used rover power. How will it get power once I abandon it on the surface? Well, it turns out it's going to be attached to a 2 square meter solar cell. That'll be plenty. And I put a small rechargeable battery in the container to tide it over during nighttime (again, harvested from the spare EVA suit).

The next problem is heat, or the lack thereof. As soon as I take this thing out of the rover, it'll start cooling down mighty fast. Once it gets too cold, the electronics will stop working entirely.

So I needed a heat source. And my electronics kit provided the answer. Resistors. Lots and lots of them. The camera and power meter only need a tiny fraction of what a solar cell can make. So I'm dumping the rest of the energy through resistors.