NASA makes another mistake?

[Hungry4info]

Sorry to bug you with another bug, but if it hasn't been addressed, I think it should.

On November 11, 2005 Cassini hits Dione. (sorry I can't give you more information) Not sure NASA planned for that.

I found this out while looking for the next passage of Titan by Cassini. I'm afraid I don't know much about the orbits of either Dione or Cassini... sorry.

Unless There's a giant cave through Dione that Celestia can't draw.

[jgrillo2002]

Where did you get this information from? from my research and viewing of the official Cassini website, there has been no report about this so this means that there is no proof that it will hit Dione.

[Malenfant]

I think he means that in Celestia it hits Dione on that date.

Chances are the Cassini xyz in Celestia that he is using is wrong, or the orbital positions aren't accurate.

I'm pretty sure that NASA would notice something like that if it was true - their trajectories are pretty spot on nowadays .

[Spaceman Spiff]

Hungry4info is correct in his observation of what Celestia shows, as I've seen the same thing. However, it's not the case that Cassini will hit Dione, it will pass very close, about 200km away, I think.

What's happened (I suspect) is that the XYZ for Cassini's path has two points that straddle Dione's position at the slight bend that Cassini will make (due to Dione's gravity). Celestia makes objects with XYZ trajectories move on straight lines between sample points, not a smooth, fitted curve. That 'short-cut' happens to go through Dione.

It's like the planets-not-on-their-orbit's problem (due to orbit sample points be too far apart), except that planets are always at the 'right' place on the orbit, but the orbit's line segments cut across the 'wrong' places.

Ideally, XYZ trajectory sampling should be optimised to increase sample points as the curvature of the trajectory gets sharper - but that's another one for the outstanding 'code todo list'.

Spiff.

[Hungry4info]

Thanks spiff.