New Venus Express addon

[jestr]

Hello everyone,I am currently working on a new Venus Express addon,since the real craft goes into orbit around Venus in a couple of weeks time.I have finished the model and made an xyz file from the orbit data available on JPL Horizons computer,and have made a basic EllipticalOrbit definition for the polar orbit of the craft from April 11 onwards.The orbit I have used is this

Code: Select all


EllipticalOrbit
 {
  Period  1
  SemiMajorAxis  6302
  Inclination 90
  MeanAnomaly  300
 }



If anyone has a better,more accurate orbit for the craft (or if I have forgotten something vital) can they let me know so I can correct it before uploading the whole addon to the Motherlode.

Here is a screenshot of the new model



Cheers,Jestr

[selden]

Accorcing to
http://sci.esa.int/science-e/www/object ... ctid=37357
the orbit will be highly eccentric, with a pericenter altitude of 250 km and apocenter altitude of 66000 km.

so
6502+250 = 6752
6502+66000 = 72502

Eccentricity = (72502-6752)/(72502+6752) = 0.8296

SemiMajorAxis = (72502+6752)/2 = 39627

[jestr]

Thanks Selden,I am trying to get the xyz orbit to match as close as possible with the elliptical one so its best I get the elliptical one right first.Would the pericenter be close to where the orbit insertion takes place?according to the xyz orbit the craft flies into Venus at around the time of orbit insertion (maybe a limitation of Vsop though),so 250km seems about right for this time.Jestr

[selden]

The orbit page doesn't say.
The initial orbit, however, is not the final orbit: there will be seven maneuvers over a period of three weeks or so that change the orbit significantly each time.

See http://sci.esa.int/science-e/www/object ... ctid=38947

[jestr]

Actually the xyz orbit from Horizons takes care of all these manoeuvres up until May 7th 2006 and the craft is in its final orbit,but Venus is in the wrong position throughout and the craft keeps ploughing through the north of Venus.Cheers for the help Selden,I tried changing the Venus orbit from VSOP to JPL but it didnt help,I guess I'll have to try to edit the xyz orbit a little,Jestr

[selden]

You could try using a SampledOrbit for Venus for that time interval. That may or may not help.

In the past, it turned out that many more samples were needed in a trajectory when it changed quickly near its pericenter. Celestia doesn't (or can't) interpolate properly when an xyz trajectory changes direction too quickly between sample points.

[jestr]

OK,people,I have uploaded my new models of Venus Express to the motherlode.You can find the DDS version here
http://celestiamotherlode.net/creators/jestr/venus_express_dds_v1.0.zip

and the JPG version here
http://celestiamotherlode.net/creators/jestr/venus_express_jpg_v1.0.zip

The models in both formats is cmod format,if you cant use these,there are 3ds versions (also JPG and DDS) available thanks to Psykotik.
dds version here
http://www.ikiru.ch/celestia/Archives/hors_site/venus_express_3ds_dds.zip

and jpg version here
http://www.ikiru.ch/celestia/Archives/hors_site/venus_express_3ds_jpg.zip

Just in time for orbit insertion,hope you like it,Jestr