Deep Impact probe uses Express Logic’s ThreadX RTOS, Green Hills Software’s MULTI IDE

Oct. 1, 2005
NASA’s Deep Impact spacecraft, which collided with a comet this past summer, used software technology from Express Logic in San Diego and Green Hills Software in Santa Barbara, Calif.

By John McHale

PASADENA, Calif. - NASA’s Deep Impact spacecraft, which collided with a comet this past summer, used software technology from Express Logic in San Diego and Green Hills Software in Santa Barbara, Calif.

Deep Impact, the spacecraft pair designed and built by Ball Aerospace & Technologies Corp. in Boulder, Colo., accomplished its goal of colliding with deep-space comet Tempel 1 and excavating material from the nucleus of the comet on July 4.

The mission’s Flyby spacecraft and the impactor spacecraft featured sophisticated technology, including three advanced instruments for imaging the comet. The NASA Jet Propulsion Laboratory in Pasadena, Calif., was in charge of the Deep Impact project.

The ThreadX real-time operating system (left) from Express Logic flew on NASA’s Deep Impact mission, which targeted the comet Tempel1, pictured here.
Click here to enlarge image

Deep Impact used a medium-resolution imager (MRI), a high-resolution imager (HRI), and an impactor targeting sensor (ITS). The HRI is the primary science instrument for the mission, composed of a telescope with a 30-centimeter (11.8 inch) aperture, an infrared (IR) spectrometer, and a multispectral CCD camera.

Express Logic’s ThreadX real-time operating system (RTOS) managed the operation of the CCD camera controllers in all three instruments used on the Deep Impact mission. ThreadX controlled the HRI, the MRI, and the ITS.

Each instrument guided the impactor onto a collision course with the comet and took the science data before, during, and after impact with the comet. In all three controllers, ThreadX managed the scheduling of application threads, performed interrupt servicing, and passed the messages needed to enable the cameras to perform their difficult mission, says John Carbone, vice president of marketing at ThreadX.

ThreadX was running on a ruggedized Sparc processor from Atmel in San Jose, Calif., Carbone says.

ThreadX is a small-footprint, highly responsive RTOS, ideal for applications in resource-constrained systems like those aboard the Deep Impact spacecraft, Carbone says. ThreadX is designed to be simple to learn and use, helping developers save time and money, Green Hills officials say.

The RTOS is specialized for embedded applications that do not require the use of a bulky complicated RTOS, Carbone says. ThreadX is “small in memory footprint, but fast with an easy-to-use application programming interface,” he explains. The system is also easier to certify for requirements such as FAA DO-178B because it does not have a lot of code, Carbone adds.

Most of the market for it is high-volume commercial handhelds, “but once in a while we get do projects like Deep Impact,” Carbone says.

ThreadX is integrated with Green Hills Software’s MULTI IDE and includes kernel-aware debugging, pre-configured project building, source code browsing and EventAnalyzer execution logging for system and application event monitoring.

All software for the project was developed using MULTI IDE. MULTI is a complete integrated development environment for embedded applications using C, C++, Embedded C++, and FORTRAN. MULTI runs on Windows, Linux, or UNIX hosts and supports remote debugging to a variety of target environments. MULTI provides a direct graphical interface with all Green Hills compilers, and supports multilanguage development and debugging.

Ball Aerospace was able to meet the project schedule and performance goals thanks to all the system software being developed with only MULTI IDE, says Dan O’Dowd, president of Green Hills Software.

For more on Green Hills Software visit For more on Express Logic visit

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