Cassini Controllers Overcome Software Glitch

NASA mission controllers said Friday that Cassini remains in "an excellent state of health and is operating normally" – although they did encounter a serious software problem last week that required a bit of jury-rigging with the Saturn spacecraft's software.

The problem arose during transmission of a complex command sequence. Controllers at Jet Propulsion Laboratory learned to their surprise that the sequence had used so much of Cassini's memory that it could accommodate only 720 more words of code – not enough to record the entire command. So controllers decided to send the sequence in pieces, and allow the spacecraft to reassemble them after it received the complete message.

That approach caused a second and potentially more serious problem, because when controllers attempted to send the transmission piecemeal, they discovered errors in the spacecraft's software prevented it from reconstituting the commands. Worse, controllers found that their additional transmissions would require up to 13,000 words of memory, so failure to solve the problem could have left Cassini crippled.

Controllers fixed the problem, however, and have since developed a new technique to send a single code sequence in as many pieces as necessary to accommodate the software limitations.

Further analysis showed the software error appeared because of an incompatibility between one of the sequence-transmission directives and the spacecraft's basic software package. Controllers said they definitely have worked around the problem and they do not expect a repeat.

Meanwhile, controllers said they have successfully recharged Cassini's hydrazine tank to bring the spacecraft's thrusters up to full capacity in advance of its planned lower-altitude Titan flybys, starting with the one scheduled for July 22. They said they do not expect another recharge will be necessary for at least 10 months.

So far in its mission, which reached Saturn on July 4, 2004, Cassini's cameras have recorded nearly 69,000 raw images – including the one above of the planet's horizon as its moons Dione and Janus glide past.

A few craters are visible on Dione (1,126 kilometers, or 700 miles across). Janus (181 kilometers, or 113 miles across) is slightly blurred due to its motion during the exposure.

The rings appear essentially edge-on in this view, as the Cassini spacecraft continues its recent activities close to the ring plane. Cassini took the image with its narrow-angle camera on March 10, using a filter sensitive to wavelengths of infrared light centered at 750 nanometers. The image was acquired at a distance of approximately 2.9 million kilometers (1.8 million miles) from Saturn. The image scale is 17 kilometers (11 miles) per pixel.

Copyright 2006 by Space Daily, Distributed United Press International

Related stories:

Shuttle gives space station a mile-high boost
(AP) -- Space shuttle Endeavour provided an orbital lift to the attached international space station on Friday as the astronauts encountered more problems with a new water recycling system.
Shuttle, astronauts prep for mid-mission reboost
(AP) -- Astronauts at the international space station prepared to work on a urine-recycling contraption and re-fire the space shuttle's thrusters Friday, before enjoying a half-day off to reboost their own energy.
Professor Finally Publishes Controversial Brain Theory
(PhysOrg.com) -- In the late '90s, Asim Roy, a professor of information systems at Arizona State University, began to write a paper on a new brain theory. Now, 10 years later and after several rejections and resubmissions, the paper “Connectionism, Controllers, and a Brain Theory” has finally been published in the November issue of IEEE Transactions on Systems, Man, and Cybernetics – Part A: Systems and Humans.
Family-friendly Wii out to win battle-loving gamers
Eric Nofsinger is betting that Nintendo's hot family-friendly Wii videogame consoles can win the hearts of "hardcore gamers" that lust for battle in action-packed virtual worlds.
Stanford's 'autonomous' helicopters teach themselves to fly
Stanford computer scientists have developed an artificial intelligence system that enables robotic helicopters to teach themselves to fly difficult stunts by watching other helicopters perform the same maneuvers. The result is an autonomous helicopter than can perform a complete airshow of complex tricks on its own.
Intel Unveils Extensible Host Controller Interface Draft Specification to Support USB 3.0 Architecture
Intel Corporation today announced the availability of the Extensible Host Controller Interface (xHCI) draft specification revision 0.9 in support of the USB 3.0 architecture, also known as SuperSpeed USB. The xHCI draft specification provides a standardized method for USB 3.0 host controllers to communicate with the USB 3.0 software stack.
Intel Outlines Plans for New Category of Smarter, Purpose-Built 'System on Chip' Designs
As Internet access continues to be added to all kinds of computers and devices, Intel executives outlined a plan to use its chip design expertise, factory capacity, advanced manufacturing techniques and the economics of Moore's Law to usher in a new category of highly integrated, purpose-built and Web-savvy System on Chip (SoC) designs and products. The company also unveiled its first eight such products under its Intel EP80579 Integrated Processor family for security, storage, communications, and industrial robotics.
Transforming buses into mobile sensing platforms
Public buses could be transformed into mobile sensing platforms, sending out information for traffic management, road safety and even hazard alerts thanks to the work of European researchers.

News discussion:

Space & Earth science news