Celestia Forums

Ephemeris Type [change] : VECTORS
Target Body [change] : Mars [499]
Coordinate Origin [change] : Sun (body center) [500@10]
Time Span [change] : Start=2007-02-25 01:00, Stop=2007-02-25 02:00, Step=1 m
Table Settings [change] : output units=KM-S; quantities code=2
Display/Output [change] : default (formatted HTML)

rosetta [-226]
Rosetta.xyzv 25/05/2007 01:00 ? 25/02/2007 02:00 1 min

mars [499]
mars.xyzv 25/05/2007 01:00 ? 25/02/2007 02:00 1 min

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solarsys.ssc



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# Flybys:
# Earth : 2005-Mar-04 22:10 UTC (8340 km from center, ~1962 km altitude)
# Mars : 2007-Feb-25 (250 km altitude)
# Earth : 2007-Nov-13 20:57 UTC (11,678 km (center), alt=0.83 Earth-radii)
# 2867 Steins : 2008-Sep-05 (1700 km, 9 km/s)
# Earth : 2009-Nov-13 07:35 UTC (alt=2491 km, lat=-6.6 deg, long.=112.7 deg)
# 21 Lutetia : 2010-Jul-10 (3000 km, 15 km/s)


25/02/2007 01:44:17
Rosetta (YES xyzv) <= 260km => MARS (YES xyzv) Radius = 3389.9 km

25/02/2007 01:44:17
Rosetta (YES xyzv) <= 254km => MARS (YES xyzv) Radius = 3396 km

25/02/2007 01:44:02
Rosetta (YES xyzv) <= -56km => MARS (NO xyzv) Radius = 3389.9km "vsop87-mars"

25/02/2007 01:44:02
Rosetta (YES xyzv) <= -62km => MARS (NO xyzv) Radius = 3396 km "vsop87-mars"

I found this too, when using spice kernels.
I was wondering whicht position isn't correct: Mars or Rosetta.
Same thing for the Earth flyby of Rosetta.

CAP-Team wrote:I found this too, when using spice kernels.
I was wondering whicht position isn't correct: Mars or Rosetta.
Same thing for the Earth flyby of Rosetta.

ftp://naif.jpl.nasa.gov/pub/naif/ROSETTA/kernels/

help SSC

celestia 1.6.0.xxxx

The VSOP87 theory isn't as accurate as the table-based calculations of planet positions like the JPL's DE 405 ephemeris and SPICE kernels. Also, Celestia isn't using the complete VSOP-87 series--terms below a certain threshold are dropped in order avoid extra calculation. But even these extra terms aren't adequate for space mission simulation: if you need more accuracy, use SPICE kernels or JPL ephemerides.

--Chris

ok

Hmm well ALL my solar system bodies use SPICE kernels for ephemeris, so this should be accurate, and still Rosetta flies through Mars and Earth

CAP-Team wrote:Hmm well ALL my solar system bodies use SPICE kernels for ephemeris, so this should be accurate, and still Rosetta flies through Mars and Earth

I guarantee you that this is not a Celestia bug. There's either something wrong in the Rosetta kernel, the solar system body kernels, or your configuration. What SPICE kernel are you using for planet positions?

--Chris

I use the latest DE421 kernels

CAP-Team wrote:I use the latest DE421 kernels

1900 ? 2050 DE421

http://naif.jpl.nasa.gov/naif/lunar_kernels.txt

non, ftp://naif.jpl.nasa.gov/pub/naif/generi ... /de421.bsp

25/02/2007 01:44:17
Rosetta (YES xyzv) <= 260km => MARS (SPICE DE405) Radius = 3389.9 km

25/02/2007 01:44:17
Rosetta (YES xyzv) <= 254km => MARS (SPICE DE405) Radius = 3396 km

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25/02/2007 01:44:17
Rosetta (YES xyzv) <= 261km => MARS (SPICE DE421) Radius = 3389.9 km

25/02/2007 01:44:17
Rosetta (YES xyzv) <= 255km => MARS (SPICE DE421) Radius = 3396 km