Galileo travelling through Jupiter and Callisto...

Report bugs, bug fixes and workarounds here.
Topic author
Evil Dr Ganymede
Posts: 1386
Joined: 06.06.2003
With us: 17 years 5 months

Galileo travelling through Jupiter and Callisto...

Post #1by Evil Dr Ganymede » 16.06.2003, 02:54

I'm just running through the Galileo orbiter tour of the Jovian system, starting in 1995. Right from the start, there's a problem - the orbiter seems to travel through Jupiter when it first arrives at the system! Also, it goes through the body of Callisto around 17:30 hours (PDT) on 1997 09 16 (the C10 flyby). And again at about 02:00 hours on 1999 08 14 (PDT) on the C22 flyby.

So the orbit of something - either the satellites or Galileo (more likely the latter, I think) seems to be in error here.

Topic author
Evil Dr Ganymede
Posts: 1386
Joined: 06.06.2003
With us: 17 years 5 months

Post #2by Evil Dr Ganymede » 16.06.2003, 16:07

Also, my Voyager 1 and 2 don't seem to actually fly past any planets.

Though now I'm thinking of it, I've forgotten whether these and Galileo actually come with Celestia, or if they were someone's add-ons that I incorporated later...

Posts: 1034
Joined: 16.12.2002
With us: 17 years 11 months
Location: People's Republic Of Cork, Ireland

Post #3by JackHiggins » 16.06.2003, 18:11

xyz files don't take any account of where objects are at the time of encounters, they only show the craft moving between point xyz1 and xyz2 between the julian dates on those lines.

I have a really accurate voyager 1 & 2 xyz on my site, but because galileo has so many flybys, an accurate xyz of the entire jovian orbital tour would be a really big download... I don't think anyone has made a full one yet!
- Jack Higgins
Jack's Celestia Add-ons
And visit my Celestia Gallery too!

Site Admin
Posts: 4211
Joined: 28.01.2002
With us: 18 years 10 months
Location: Seattle, Washington, USA

Post #4by chris » 16.06.2003, 18:23

There is also error in the positions of the planets, which while not significant to an Earth based observer makes a big difference if you're designing an orbiter mission! I could add more terms to the VSOP-87 series, but there are already over 1000 per major planet . . . I've been saying for some time that Celestia needs to be able to use JPL's DE-405 (or later) ephemerides for serious accuracy. The drawback is that the DE-405 data files are large enough that supplying a set for all the major planets over a thousand year timespan . . . well, it'd make a big download :) Using DE405 ephemerides from 1950-2050 and VSOP-87 elsewhere might be a reasonable compromise.



Flyby accuracy

Post #5by HankR » 16.06.2003, 23:29

Another possibility might be to allow XYZ files to specify planetocentric or satellite-ocentric coordinates (rather than heliocentric coordinates) for close approaches. Then inaccuracies in positioning the target body would not affect the position of the flyby spacecraft relative to the target.

- Hank

Return to “Bugs”

Who is online