There is some level of shielding from any spacecraft. We at LBNL would make Al Gore proud, our satellite is designed to have an average of 5 cm of aluminum shielding the CCDs, even when they are taking an image. This shielding is made possible by a series of mirrors, the CCDs face the mirrors and not directly into space. However, this shielding is not enough to stop the offending protons. Even if we had a backup, or redundant CCD laying in wait, that device would still degrade.

You could make the shielding infinitely thick, that would stop the protons and introduce all of the obvious problems. We are constantly flirting with the weight and size limits in our design, right now blocking 99% of the solar protons with our shielding model. However, there is still a lot of energy left in the remaining 1%.

We've actually developed other ways to deal with that last 1%. Instead of building shielding past the point of diminishing returns, we work on the design of the CCDs. We now use a device with implants that are less likely to create the defects in the first place. There are several other tricks we can play, we can change the temperature, change the readout speed, change voltages-all different ways to minimize the effects of clumsy bucket brigade in the silicon.

Is it possible to have a redundant CCD system, whereby multiple back-up CCDs are kept shielded, and can be rotated into position to gaze at the stars when the primary CCD has been damaged?Certainly multiple back-up CCDs preloaded into a telescope would be cheaper than space missions to replace them after the fact.

I think it would be difficult to shield the actual CCD you are using for imaging purposes because you would effectively decrease its sensitivity for the radiation you are trying to detect.

My two cents,

Dave Winger

Hope that a trip to Colorado in March is in your future!
btw, you're looking a little green in your blog photo… Is everything OK with you? (I mean physically speaking, not emotionally, etc.)