Cassini plasma spectrometer turns off

Jun 07, 2012 By Priscilla Vega and Jia-Rui Cook
Artist concept of Cassini spacecraft. Credit: NASA/JPL

(Phys.org) -- The Cassini plasma spectrometer instrument (CAPS) aboard NASA's Cassini spacecraft was turned off between Friday, June 1 and Saturday, June 2, when a circuit breaker tripped off after the instrument experienced some unexpected voltage shifts.

Engineers are currently investigating this issue, which they believe is due to short circuits in the instrument. In June 2011, the instrument was turned off because of similar problems, but was switched on again in March 2012 once investigators determined that tin plating on electronic components had grown "whiskers" large enough to contact another conducting surface and carry electrical current, resulting in a voltage shift. At that time, it was believed that these "whiskers" were not capable of carrying sufficient current to cause any damage, and the voltage shifts didn't have any effect on normal because the power subsystem is designed to operate in the presence of such shifts.

The cause is still under investigation, but engineers will be looking into this issue over the next few months.

Cassini launched in 1997 and has been exploring the Saturn system since 2004. The project completed its original prime mission in 2008 and has been extended twice. Cassini is now in its solstice mission, which will enable scientists to observe in the Saturn system through the northern .??

The Cassini-Huygens mission is a cooperative project of NASA, the and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.

Explore further: NASA: Engineer vital to 1969 moon landing dies

More information: More details about whiskers on the CAPS instrument can be found here: www.jpl.nasa.gov/news/news.cfm?release=2012-078 .

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User comments : 6

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gopher65
not rated yet Jun 07, 2012
I assume that this was yet another probe malfunction caused by lead-free solder? I understand the need to cut back on lead use in commercial products (like game consoles. I've read that the Red Ring of Death on the early Xbox 360 models was caused by Microsoft not accounting for the fact that lead-free solder disintegrates quickly ("whiskers") and causes shorts). But you'd think they'd make allowances for things that need to operate in a radiation filled vacuum for years or decades at a time with no servicing possible.

Given all the issues NASA has had with lead-free solder on the ISS and the shuttle I hope they consider the use of at least low-lead solder in space.

My understanding of the laws around lead-free solder was that some aerospace and space applications are excempt, but maybe they thought they could make the lead-free stuff work just as well?
HannesAlfven
2.6 / 5 (5) Jun 07, 2012
I honestly don't know if such an inference is actually a good one, but it's worth mentioning that double layers are sandwiches of plus and minus charges right next to each other in space which refuse to combine. The ionosphere is an example, and we could expect to see smaller examples of such structures surrounding heliospheric Birkeland Currents, which have already been observed to commonly connect the Earth and the Sun every few minutes. Considering that Enceladus' tiger stripes and dusty plasma outflows could be legitimately inferred to be the result of electrical machining, we should expect that our instruments might occasionally pass directly through such flows ...

http://www.thunde...03/6180/

The observation of hot poles and the movement of the hot plumes should raise alarm bells that charged particles are being funneled into the poles. On Io, the Galileo probe's camera saturated while viewing one of these discharges (not likely for lava ...).
Terriva
5 / 5 (1) Jun 07, 2012
The investigation led to the conclusion that tin plating on electronics components had grown "whiskers."
Tin is an enemy of all satellites. http://www.aciusa...5-04.htm I'm somewhat surprised, such a plating is still used in these spacecraft devices? Its risk is widely recognized. IMO it's promoted with radioactivity, which is quite intensive around Saturn.
tthb
not rated yet Jun 07, 2012
???. . . . yes, S.O.S.; but to Religion; all that's going to be too hard for people; how the rest of ALL THAT is going to fare-
Vendicar_Decarian
5 / 5 (1) Jun 08, 2012
If an engineer employee came to me and told me that his intent was to use solder that was known to degrade over time and cause shorts, that engineer would be downgraded in the company.

No doubt the usage was considered a non-problem for the projected lifetime of the mission. But given that the cost differential is zero between leaded solder and tin, it makes absolutely no sense not to use a lead/tin alloy.
gopher65
not rated yet Jun 08, 2012
Vendicar_Decarian: Lead based solder has been made illegal in many places. But, as I said above, there are exceptions for some aerospace applications. I haven't seen a list, but I assume that means commercial airliners, military uses, and manned spaceflights. No idea if unmanned probes are exempted or not.

Based on the fact that they're using a solder with a known high risk of failure (tin solder fails much faster in a vacuum), I'd hazard a guess that unmanned missions aren't exempted.

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