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SOHO Spice
http://forum.celestialmatters.org/viewtopic.php?f=18&t=617
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Author:  chuft-captain [ Mon, 20-01-14, 5:00 GMT ]
Post subject:  SOHO Spice

Hi,

Thought I'd have a go at a Spice implementation for SOHO, but something's not quite right.
Please would someone try this out and see if you can spot the problem.
Attachment:
SOHO.zip [1.33 KiB]
Downloaded 139 times

The .bsp's are sourced from here: http://umbra.nascom.nasa.gov/sdb/soho/gen/spice/
(Download each spice file into the addon's "data" folder.)

Cheers
CC

Author:  John Van Vliet [ Mon, 20-01-14, 19:18 GMT ]
Post subject:  Re: SOHO Spice

i will have a look

the kernels can be VERY confusing sometimes

think of it as the effects of a "Pan_Galactic_Gargle_Blaster"
Quote:
"like having your brains smashed out by a slice of lemon, wrapped 'round a large gold brick."

http://en.wikibooks.org/wiki/Bartending ... le_Blaster

Author:  John Van Vliet [ Mon, 20-01-14, 23:22 GMT ]
Post subject:  Re: SOHO Spice

with only a quick look so far
that ssc file is not a real one
it is missing a lot of things

like the mesh for the spacecraft

it looks like you started by using Uranus's ssc
Code:
"SOHO" "Sol/Earth"
{
    Timeline
    [
    # # Before SPICE
   # {
        # Ending "1995 12 02 00:01:02.183"

        # CustomOrbit "vsop87-uranus"

        # BodyFrame { EquatorJ2000 { Center "Sol/Earth" } }
        # #CustomRotation "iau-uranus"
    # }
    # soho_1995
    {
        Beginning "1995 12 02 00:01:01.183"
        Ending    "1996 01 01 00:01:02.183"

it is commented out
but it is missing things
like ,there is NO mesh or rotation or anything else
Code:
"SOHO" "Sol/Earth"
{
 Class "spacecraft"
 Mesh " SOHO.cmod"
Orientation [ 0 1 0 0 ] # if you did not rotate x+90
 Radius 0.1
# timeline
[
--- code ----
--- and some more ----
]
UniformRotation
# or vector or any other rotation
{
   Period ?
   Inclination ?
   AscendingNode ?
   MeridianAngle ?
   Epoch ?
}
}

Author:  chuft-captain [ Tue, 21-01-14, 12:12 GMT ]
Post subject:  Re: SOHO Spice

John Van Vliet wrote:
with only a quick look so far
that ssc file is not a real one
it is missing a lot of things

like the mesh for the spacecraft

it looks like you started by using Uranus's ssc

it is commented out
but it is missing things
like ,there is NO mesh or rotation or anything else

I should have made it clear that I'm only working on the orbit first (which is why the models and textures folders are empty).
I plan of course to add a Mesh and it's rotation definition when it's required, however, none of that is required simply to get the orbit working correctly.

Note that if these .bsp definitions were working correctly then SOHO should orbit the L1 point between Sun and Earth (~ 1.5 million km from Earth), but it's not behaving in that way.

Maybe, you can answer this question John:
In SPICE implementation, is it necessary for every higher level object in the hierachy to be implemented in SPICE before subordinates will work?
If that's the case, then it's possible that I haven't yet got a working SPICE file for Earth (which SOHO's orbit is centered on), in which case that may be the cause of the problem.

I'll check this. EDIT: It turns out that I DO have a SPICE definition for Earth:
Code:
Modify "Earth" "Sol"
{

    Timeline
    [
    # Before Spice
   {
        Ending "1899 07 30 00:00"

        CustomOrbit "vsop87-earth"

        BodyFrame { EquatorJ2000 { Center "Sol" } }
        CustomRotation "iau-earth"
    }
    # de421
    {
        Ending    "2053 10 08 00:00"

        OrbitFrame { EclipticJ2000 { Center "Sol/Earth_bary"}}

        SpiceOrbit
        {
            Kernel "de421.bsp"
            Target "399"
            Origin "3"

            BoundingRadius 1e10
        }

        BodyFrame { EquatorJ2000 { Center "Sol" } }
        CustomRotation "iau-earth"
    }
       
    # After Spice
    {
        CustomOrbit "vsop87-earth"

        BodyFrame { EquatorJ2000 { Center "Sol" } }
        CustomRotation "iau-earth"
    }

    ]


}


Regards
CC

Author:  chuft-captain [ Tue, 21-01-14, 14:30 GMT ]
Post subject:  Re: SOHO Spice

OK,

So I made a few changes to the SSC and the SPICE orbit is now being drawn...
Attachment:
zSOHOSpice.zip [731 Bytes]
Downloaded 115 times


...BUT .... only up to the 1998a.bsp.

From 1998b.bsp --> 2014, there's no action!

The reason for the 2 (a and b) files for 1998 is that all communication was lost with the spacecraft in Aug 1998, and then it was re-acquired in Sep 1998, so there is a period between 1998a and 1998b where there is no SPK data.
This happens to also be the point at which the action stops in Celestia.
Is there some limitation in Celestia perhaps that requires the orbit data to be contiguous and continuous?

There seems to be a problem re-starting the orbit with the 1998b.bsp file (i.e. after the gap in the data).

CC

Author:  John Van Vliet [ Wed, 22-01-14, 7:33 GMT ]
Post subject:  Re: SOHO Spice

this below works
Code:
"SOHO" "Sol"
{
  Class "spacecraft"
  SemiAxes   [ 3 3 3 ]



  OrbitFrame { EclipticJ2000 { Center "Sol/Earth"}}


  Beginning   "1998 09 25 18:58:03.182 "
  Ending      "2014 02 01 00:01:07.183"

  SpiceOrbit
  {
    Kernel
    [

    "soho_1998b.bsp"
    "soho_1999.bsp"
    "soho_2000.bsp"
    "soho_2001.bsp"
    "soho_2002.bsp"
    "soho_2003.bsp"
    "soho_2004.bsp"
    "soho_2005.bsp"
    "soho_2006.bsp"
    "soho_2007.bsp"
    "soho_2008.bsp"
    "soho_2009.bsp"
    "soho_2010.bsp"
    "soho_2011.bsp"
    "soho_2012.bsp"
    "soho_2013.bsp"
    "soho_2014.bsp"
    ]
    Target "-21"
    Origin "399"
    Period  90
    BoundingRadius 1e10
  }

  PrecessingRotation
  {
    Inclination                5   
    AscendingNode       5   
    Period                      5     
    PrecessionPeriod    5
  }

}



a timeline is not needed for this because the orbit "Origin " never changes and no breaks in time

it works for AFTER 1998 -- the break in time

for say Cassini
it encountered Jupiter first and the kernels used Jupiter as the origin for that part

and Messenger , that one is a mess with Earth and two Venus flybys


from HORIZONS you can get the orbital element the start of the 1998 b and use that for something like i did with jupiters and saturns moons
Code:

the 1995.bsp
the 1996.bsp
the 1997.bsp
the 1998a.bsp
---- ending date

then beginning date in Aug.  using the Sep.1998 orbital elm.
and ending on a over lap of a day

 EllipticalOrbit
      {
        Epoch         
        Eccentricity           
        AscendingNode         
        SemiMajorAxis           
        ArgOfPericenter       
        MeanAnomaly           
        Inclination             
        Period               
      }

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