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Cassini Probe Has Camera Problems

Posted by chrisd on from the chris-knight-school-of-optics-clarity dept.

xX_sticky_Xx writes "The BBC is reporting that the last billion dollar NASA probe, Cassini, (enroute to Saturn) is suffering from an unknown source of contamination on its narrow field camera. NASA has attempted to alleviate the contamination, which is causing a haze to appear around images, by "defrosting" it, with so far limited success. Another attempt will be made in January. If this problem can't be resolved this will be extremely disappointing. Cassini is set to expand our knowledge of Saturn more than Galileo did for Jupiter."

1 of 142 comments (clear)

  1. Source of contamination by chazR · · Score: 5, Insightful

    The source of contamination *has* to be the spacecraft itself.

    If the contamination were external, it would have had a signifigant (measurable) effect on the momentum of the spacecraft. The space through which it is travelling is pretty much completely empty anyway.

    That leaves one plausible possibility: Cassini is leaking something that is condensing on the cold (*very* cold) bits. The most likely cause is a small propellant leak. As far as I know, the spacecraft has three propellants on board, N2O4, N2H4 an monomethyl hydrazine. I'm too lazy to look up the charecteristics of these, but their boiling points differ.

    A heating cycle of the lens seems to have helped. I would be *very* surprised if the data from the heating cycle didn't give them a good clue as to the exact contaminant by looking at the amount removed by a known heat input (latent heat of vapourisation)

    The big worry is that the leak will leave the spacecraft with insufficient fuel for orbital insertion (unlikely - it's almost entirely a gravity-assist trajectory) or for manoeuvering. That would be bad.

    I may, of course, be completely wrong.