It may seem like it's taking years to get the Mars rovers off the ground, and it is. These spacecraft are complex. Their solar panels are small. Their batteries are small. The time they're expected to run is not too long. But, they'll be doing big science. Right now, the rovers will be launched around May of 2003 and arrive on Mars in January of 2004. That may seem like a long time. But to those working to get the rovers built and tested, it's not much time at all. There is so much work to be done; there's so much to be learned.
Landing on Mars is like going camping on another planet. The only things you're going to have are the things you brought with you. You don't want to take anything you don't need, because that extra weight may ruin your trip. If something breaks or stops working, well, there's almost no way to fix it. You're stuck two hundred million kilometers from the nearest town. On Mars, it's bitterly cold. The air, such as it is, is very thin. Our machine will have traveled through the cold vacuum of space for a several months. Then it will have bounced down to land on the rocky Martian surface. Designing a spacecraft is a challenge; it takes years.
Figuring out what you'll need on Mars is probably the first thing to do. We need cameras. Do we need one or two, or three? Do we need a magnetometer, a spectrometer, or even a speedometer? Then, we have to figure out where to mount these instruments on the rover. We need to figure out what the rover will look like. Will it have three wheels, or six, or nine? Or, will it have treads and skids with no wheels at all? Every shape on a spacecraft comes out of someone's head. Every part of the spacecraft starts with an idea. If you're working on it, you need to figure out how to design and develop your idea. After that, you have to build and test your idea. The spacecraft and its science instruments go from computer drawings to metal and plastic and to the software to drive them. About a year before launch, the whole spacecraft, the entire "flight system" is put to the test. Soon it's time for ATLO: Assembly, Test and Launch Operations.
At each phase of a spacecraft's construction, there is a seemingly endless list of meetings, reviews, documents and deadlines-- deadlines that must be met in order to keep the mission on schedule for launch. The pace can be grueling. If something goes wrong, the problem must be dealt with quickly. Something as small as wires that don't quite allow the Miniature Thermal Emission Spectrograph (Mini-TES) instrument to work properly can slow the design way down. If commonplace items like the resistors for the Pancam electronics won't fit on the circuit boards, well, you've got to fix it right away. If you're building a circuit at home, you might just go get a bigger box to put it in. On the way to Mars, you just don't have that option. Think fast.
Mini-TES wires and Pancam resistors are just a few components of a spacecraft that has thousands and thousands of parts and millions of lines of software code! Every subsystem must be tested and re-tested to make sure it can endure the vibration of liftoff, months of space travel, and then a drop, bounce, and roll landing on the Martian surface. Then the whole set-up has to still be able to operate properly for several months in the extremely harsh environment of another planet.
But preparation of the spacecraft and all its parts isn't a complete picture of what's going on. There are so many people involved that the picture is much bigger. Think of the spacecraft as being the hub of a wheel. The wheel is the entire mission. Its spokes are the many, many groups of people who have their own expertise to contribute. They include people who build the science instruments, people who select the landing sites, people who plan what will happen on the surface of Mars, and people who make sure the rover is mechanically sound. Scientists and engineers have to be trained to drive the rovers while they are on the Martian surface. They need to master complex computer software, and figure out how to handle all the data that the rovers will be collecting and sending back to Earth. But no matter how much expertise they have, there is still a great deal they don't know. There is so much to learn.
Months and years disappear very quickly, when there's so much going on. Before you know it, the Mars Exploration Rovers (MERs) will be on their launch pads ready to explore another world.
