Celestia Forums

Hy.

I was playing with Celestia to see a Cassini getting closer to Saturn, and was just curious when will it end its way around it (2008 08 09), so I run time a little bit faster. When that date came, the name Cassini on screen didn't disapear. I found that THEY forgot to place a line

Ending 2454687.5

in original spacecraft.ssc in data directory, so when XYZ finish the object doesn't turn off. So YOU can do this

This is not a bug that could annoy everybody, but still it is strange to see it hanging in one place. I also think that when original mission ends, and if everything goes right, NASA guys will do same thing as they did with Galileo - continue mission. Real endind of mission is not clear so till then let's keep things as right as possible.

PS.: I also notised some strange movement of Huygens probe: it detaches, moves forwards, then very rapidly moves backwards and then again moves away. This must be a problem with XYZ.

JimBim wrote:I found that THEY forgot to place a line

Ending 2454687.5

in original spacecraft.ssc in data directory, so when XYZ finish the object doesn't turn off.

THEY didn't forget ... when we know when and how the mission ends, I'll put an ending date in.

JimBim wrote:PS.: I also notised some strange movement of Huygens probe: it detaches, moves forwards, then very rapidly moves backwards and then again moves away. This must be a problem with XYZ.

Must be a rounding error in there somewhere. I'll take a look.

Grant

When I ran Cassini forward to the end, I found it seemed to end up on a perpetual very long orbit around Saturn. Was I just not running it forward far enough?

Evil Dr Ganymede wrote:When I ran Cassini forward to the end, I found it seemed to end up on a perpetual very long orbit around Saturn. Was I just not running it forward far enough?

The last Julian date available from Horizons is 2454687.5 = 2008 Aug 9 00:00. so at that point in Celestia you should see Cassini freeze in place and Saturn shoot off into the distance, because Cassini's orbit comes to an abrupt end.

Grant

JimBim wrote:PS.: I also notised some strange movement of Huygens probe: it detaches, moves forwards, then very rapidly moves backwards and then again moves away. This must be a problem with XYZ.

I'm guessing that you're watching Huygens from Cassini? That's the only way I can reproduce the appearances you describe. What I think you're seeing is the effect of Cassini manoeuvring away from Huygens - if it didn't make a manoeuvre at this point, Cassini would slam into Titan, too. If you watch the pair of them from some distant viewpoint, you'll see Cassini put on burst of acceleration shortly after releasing the Huygens probe - so from Cassini's viewpoint Huygens falls away, then seems to accelerate backwards, then falls away again - but it's actually Cassini doing the manoeuvring.
I'm sure the xyz isn't perfect for this section, since the sampling isn't tight enough to reproduce the precise Cassini manoeuvre - but I think what you're seeing is a real-world event, not a mistake in the xyz.

Grant