News

Iridium Simulates Space Software with Simics

• By John K. Waters
• October 31, 2005

The next time you feel like complaining about your software management challenges, consider Don Rasure's problem: Much of the software he looks after is in space.

Rasure is director of gateway maintenance at Iridium Satellite, the company that rose in 2000 from the ashes of the bankrupt satellite phone company Iridium. The new organization has no connection to the old; it was founded by a group of private investors formed to purchase the assets of the bankrupt company.

Among those assets were the 66 cross-linked, low-orbit satellites (and a few in-orbit spares) that support the company's wireless communications service. This "constellation" is the world's largest commercial satellite network. Iridium Satellite targets industrial, government and individual customers with a need for remote communications capabilities where no other form of communication is available--ships at sea, airborne aircraft and, recently, hurricane-ravaged regions around the Gulf.

But the new company did not receive all of the basic hardware the old company had used to develop and construct the flight software that operates the satellites. And without physical access to in-orbit Iridium hardware, developing flight software to mitigate in-orbit issues is very difficult, Rasure says.

"It's tough to go out and capture a satellite and bring it back to earth," Rasure says. "So we had to come up with another solution."

At the suggestion of some Boeing engineers who work with the company, Rasure turned to Virtutech and its flagship systems simulation platform, Simics.

Simics is designed to allow software developers to model hardware so accurately that the software can't tell the difference. Any code, from application code to real-time operating systems and device drivers can run on these simulations.

Iridium uses Simics to model the space vehicle multi-processor system for unit testing. It lets the company examine how both existing and new flight software operates on the satellite, and it provides developers with a means of recreating performance issues for in-depth inspection and diagnosis. By simulating the satellite hardware with the Simics tool, the company can accelerate development and validations of flight software modifications, he says.

Logistics was one factor in Iridium's decision to ramp up its virtualization capabilities with Simics; budget and labor considerations figured in, as well. The new Iridium is a smaller operation than its predecessor. The original constellation, which Rasure says is still working exceptionally well, was built by hundreds of engineers; Iridium Satellite employs roughly 150.

"This way, we didn't have to go out and spend a gazillion dollars replicating hardware," Rasure says. "Now, we simulate some of the hardware, and we're able to use the modeling tool to build models from those simulations that we can run in the lab. It has been one of the tools that have allowed us to move forward with our goal of improving the quality of the products and services we provide."

Virtutech's CEO John Lambert characterized the Iridium implementation of Simics as “...another example of the successful utilization of software-based simulation in a market where the end product is literally out of this world.”