Iridium: Developing Satellite Software Using Simics


Iridium Satellite was founded in 2000 by a group of private investors that held the assets of the bankrupt satellite phone company, Iridium. Among those assets were the 66 cross-linked, low-orbit satellites and a few in-orbit spares that supported the company’s wireless communications service. However, the new company did not receive all of the basic hardware the old company used to develop and construct the flight software that operated the satellites.

Over time, portions of each satellite became outdated or damaged. The constellation was still working well, but Iridium Satellite needed a cost effective and efficient method to test and debug the flight software before it was uploaded to the satellite system.

Iridium Satellite’s unique problem was that it had no physical access to in-orbit hardware: Developing flight software to mitigate in-orbit issues from 485 miles away is, understandably, a very difficult task. Using a proxy of the actual satellite hardware created unreliable results, and the expensive alternative — using real hardware — was an unsupportable cost.

"It’s tough to go out and capture a satellite and bring it back to earth," said Don Rasure, director of gateway maintenance at Iridium Satellite. "So we had to come up with another solution."

Since Iridium Satellite is a smaller operation than its predecessor, budget and labor considerations offered another significant challenge in maintaining the constellation. The original constellation was built by hundreds of engineers; the new Iridium Satellite employs roughly 150 people.


At the suggestion of some Boeing engineers who work with the company, Rasure turned to Virtutech and its flagship full system simulation platform, Simics. After a thorough review of the possible software development options available on the market, Iridium chose Virtutech Simics because of the significant cost savings and unique value proposition that Virtutech offers.

By deploying Virtutech Simics, Iridium Satellite is able to debug software with the highest quality standards before it is uploaded to the spacecraft, without the need for actual hardware. Simics enables Iridium Satellite software developers to model hardware so accurately that the software cannot tell the difference. All code, from application code to real-time operating systems and device drivers, can run on Virtutech’s simulation model.

Iridium Satellite currently uses Virtutech Simics to model the space vehicle multi-processor system for unit testing, eliminating the need for hardware. The company is able to examine how both existing and new flight software operates on the satellite. Iridium Satellite software engineers now have a way to recreate performance issues for in-depth inspection and diagnosis, giving them the flexibility to isolate problems when running code.


By simulating the satellite hardware with Simics, Iridium Satellite greatly increases development speeds and validations of flight software modifications for the company’s satellite constellation.

"With Simics, we were able to locate defects in the flight software within hours, versus days of using traditional hardware in the loop testing," said Joe Pizzicaroli, Iridium Satellite vice president for satellite and launch operations. "Having no physical access to on-orbit Iridium hardware on the ground makes developing flight software to mitigate on-orbit issues very difficult. By simulating the satellite hardware with the Simics tool, development and validations of flight software modifications are accelerated."

While ground simulation has been a staple of satellite software development and upgrades for years, the approach of replacing the hardware with software that mimics its behavior enables relatively small operators like Iridium Satellite to save time and money.

"This way, we didn’t have to go out and spend a gazillion dollars replicating hardware," Rasure said. "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."

About Iridium

Iridium Satellite LLC is a provider of global wireless satellite communications services with complete coverage of the earth. The company delivers essential communications services to and from remote areas where no other form of communication is available: ships at sea, airborne aircraft and, recently, hurricane-ravaged regions around the Gulf.

Iridium Satellite makes this communication possible through its constellation of 66 low-earth orbiting (LEO), cross-linked satellites and 11 in-orbit spares — the world’s largest commercial satellite network. Iridium Satellite serves a variety of industries, including maritime, aviation, government/ military, emergency/ humanitarian services and the U.S. Department of Defense.

Iridium Satellite LLC
Arizona, USA
Industry: Communications
Products: Simics Developer, Simics Model Builder, Power PC and other models
Users: Payload software development team, Payload software unit test team
Benefits: Robust unit test, Inaccessible flight hardware available on desktop, "Test as you fly, fly as you test"


Phone: +1 408-392-9150
Fax: +1 408-608-0430

Asia Pacific
Phone: +65 9780-1295

Europe, Middle East, and Africa
Phone: +46 8-690-0720
Fax: +46 8-690-0729

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