Macs making inroads on NASA's Cassini mission

Editor's note: This story was first published on Friday, April 15, but was removed to verify some facts. Thank you for your patience through this process.

The next time NASA launches a craft into space, it may receive many of its navigational instructions from programs run on the Mac. That's a possibility espoused by the Jet Propulsion Laboratory's (JPL) Nathan Strange and Troy Goodson, two Cassini mission navigators who perform their critical work on Dell machines running Linux but also keep Macs at their desks for other uses. Macs sit next to Linux boxes on most of the 14 navigators' desks.

Strange, who uses a Dual Processor 2GHz Power Mac G5 as his second computer, told MacCentral: "Macs can do everything Linux can, and a G5 performs as well as a Xeon, and better than a Pentium 4 on our software. The issue is that the Linux workstations have a very tightly controlled configuration and extra security, and they've been tested more thoroughly."

For example, Strange can fine-tune Cassini's trajectory on his G5 with CATO (Computer Algorithm for Trajectory Optimization), but he must replicate the work on the Linux box to ensure accuracy. "What if I install an upgrade like 10.3.9 and suddenly a subtle error creeps into a library and all of my results are wrong, but the error is too small to notice?" he asks. Clearly, the answer could be a mission-endangering catastrophe.

Macs for everything else

When it comes to non-critical tasks, however, Strange is more than happy to turn to his G5. For example, he uses it to run SOAP (Satellite Orbit Analysis Program), which generates 3D animations of spacecraft motion relative to the sun, moon and other celestial objects. In fact, JPL's control center is dominated by Sun computers, but when someone needs to show an animation of Cassini's trajectory on the large display screen, they hook up a PowerBook and run it with SOAP.

Strange also employs Quick, an orbital mechanics utility, on the G5 to generate results that help him set up applications on the Linux box. He uses the UNIX utility SSH to transfer files between computers.

And when he needs to write memos or create graphs, he's usually glad that he didn't choose a Windows machine as his other computer. He noted: "PDFs that are added to PowerPoint in Windows get rendered as bitmaps, which look awful. Meanwhile, I can use the accessibility option on the Mac to zoom in on graphs when I'm presenting them in a conference room. It saves a lot of time, because I don't have to create graphs with different levels of zoom."

Almost there

The navigation team almost moved completely to Macs in 2003, but not all of JPL's navigation tools had been ported to OS X yet. Apple also hadn't officially announced the G5, so hardware requirements led them to the Dell machines running Linux. However, many of the applications, such as CATO, were created with Fortran, leaving open the possibility of completing the porting process and using Macs for critical tasks during a future NASA mission.

According to Goodson, who Beta tested a lot of software during the porting process, the release of Mac OS X changed many minds at JPL because "it has a command line, which makes it much easier to develop tools. There was a lot more interest in the Mac with [the open source UNIX environment] Darwin under the operating system." He chose a PowerBook G4 as his second computer.

Strange noted that PowerBooks have become increasingly popular at JPL. "There's been a new thing the past few years with people bringing laptops to meetings so they could work during the parts that didn't apply to them," he explained. "Once it hit critical mass, everyone wanted one."

While Goodson and Strange would both prefer to have a single Mac on their desks, Strange said that the current two-computer configuration "is the bureaucracy side of space flight. I joke that this job combines a thirst for adventure with a healthy attention to detail. There are lots of small details that can cause you to lose a spacecraft if they are messed up."

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