NASA: 'Extreme programming' controls Mars Lander robot

Computerworld - Scooping up soil samples and searching for elements that could support life on Mars isn't just an adventure for the Mars Lander and the robotic arm doing the scooping.

It's also an adventure for the approximately 30 engineers and programmers at NASA who are tasked with writing and testing 1,000 to 1,500 lines of software code and then beaming it about 170 million miles away — every day.

Matthew Robinson, the robotic arm flight software engineer at the Jet Propulsion Laboratory, said the team has to write the code sequences to run different parts of the Phoenix spacecraft, including the robotic arm, the cameras and analysis equipment. One mistake and the Lander sits idle for a day, wasting precious time that could be used to discover if the planet can support life.

So far, all the code they've beamed up to Mars in the past week has worked.

"It's a challenge because we have a two- to three-day strategic plan, and then each day that plan is refined," Robinson told Computerworld. "They decide on the final plan that day. You have to build 20 to 30 sequences, and each can have 50 lines of code in it. And they have a lot of interplay between different instruments, so you have to make sure the sequences are not just working, but working together.

"Building the sequences is an extreme programming challenge every single day," he added.

And the developers, who used the C programming language to build their own software for a Linux operating system, are expected to be dealing with that challenge for about three months. The Mars Lander, which is on a one-way trip, is slated to gather and analyze samples throughout the summer months. After that, the planet's temperature will drop well below the current safe range of minus 170 degrees Fahrenheit to 32 degrees Fahrenheit, causing the Lander to freeze up and stop working.

The mission is focused on collecting ice and soil samples that can be analyzed in eight different ovens, four wet chemistry cells and a microscopic imager on the Lander. Robinson explained that they're not looking for life; they're looking for the elements that support life.

The robotic arm, which weighs between 20 and 30 pounds on Earth, is the key to the effort. The arm has a scoop attached at the end that is designed to dig up ice and soil, and then deliver it to the analysis tools. No soil, no analysis.

And keeping that robotic arm, along with other parts of the Lander, running every day is a huge chore.

Robinson said a 3-D digital elevation map was used last Sunday to write code to make the arm reach down and touch the ground. That gave the team an idea of how accurate the maps are, how easily the soil can be scooped up, and how well they can control the arm from so far away.