SPICE

[chris]

You do have to be careful to write the SSC files so all the appropriate barycenters are used. It isn't quite as obvious as one might like.

Is it actually necessary to include all the barycenters? I thought SPICE could also provide positions relative to the parent body.

It can, and Celestia's implementation of SPICE orbits is flexible enough to take advantage of this. For example, this here's a definition of Cassini relative to Saturn:

Code: Select all

"Cassini" "Sol/Saturn"
{
    OrbitReferencePlane "ecliptic"
    SpiceOrbit
    {
        Kernel "cassini.spk"
        Target "Cassini"
        Origin "Saturn"
    }
}


And here's one relative to the Sun:

Code: Select all

"Cassini" "Sol"
{
    SpiceOrbit
    {
        Kernel "cassini.spk"
        Target "Cassini"
        Origin "Sun"
    }
}


(The target and origin names in the SpiceOrbit are NAIF object names (or numeric IDs), not Celestia object names.)

There's no need to define barycenters, though you certainly could specify Cassini relative to the solar system barycenter or Saturn system barycenter. For whole mission interplanetary trajectories, either a heliocentric or solar system barycentric definition probably makes the most sense.

--Chris

[chris]

I don't know what causes the 2 km discrepancy for the February flyby. It could be that the kernel I used isn't the final one. I got it from the NAIF ftp site. In contrast, the kernel used for the other test came from the official Cassini data set 6 available from the PDS repository. I'll look again for a PDS kernel for the February flyby.

I'd just like to mention that I'm very pleased Celestia has evolved to the point where we're fussing over a 2 km discrepancy

--Chris

[t00fri]

I don't know what causes the 2 km discrepancy for the February flyby. It could be that the kernel I used isn't the final one. I got it from the NAIF ftp site. In contrast, the kernel used for the other test came from the official Cassini data set 6 available from the PDS repository. I'll look again for a PDS kernel for the February flyby.

I'd just like to mention that I'm very pleased Celestia has evolved to the point where we're fussing over a 2 km discrepancy

--Chris

Chris,

could you perhaps explain what distinguishes this host of different SPICE kernels and how a user is supposed to pick the right one without reading a fat manual??

I checked closest approaches of Cassini to Titan with one kernel for Feb 2005 and recently in 2006. In both cases the discrepancies with the mission logs were considerable (~30%). I figure that the kernel date should be close to the respective mission configuration. But I can't even read uniquely what e.g.

50825R_SCPSE_05186_05205.bsp

is going to mean...

Bye Fridger

[chris]

[
Chris,

could you perhaps explain what distinguishes this host of different SPICE kernels and how a user is supposed to pick the right one without reading a fat manual??

I checked closest approaches of Cassini to Titan with one kernel for Feb 2005 and recently in 2006. In both cases the discrepancies with the mission logs were considerable (~30%). I figure that the kernel date should be close to the respective mission configuration. But I can't even read uniquely what e.g.

50825R_SCPSE_05186_05205.bsp

is going to mean...

I'm still trying to sort that out myself . . . But, a 30% discrepancy is very surprising. What does your ssc file look like?

--Chris

[t00fri]

[
Chris,

could you perhaps explain what distinguishes this host of different SPICE kernels and how a user is supposed to pick the right one without reading a fat manual??

I checked closest approaches of Cassini to Titan with one kernel for Feb 2005 and recently in 2006. In both cases the discrepancies with the mission logs were considerable (~30%). I figure that the kernel date should be close to the respective mission configuration. But I can't even read uniquely what e.g.

50825R_SCPSE_05186_05205.bsp

is going to mean...

I'm still trying to sort that out myself . . . But, a 30% discrepancy is very surprising. What does your ssc file look like?

--Chris

I was lazy and just used Selden's add-on from the Dev list.

Bye Fridger

[cartrite]

I don't know if this would help but one of my ISIS3 data folders, /odyssey/kernels/spk/ contains a file called makedb that looks like this

Code: Select all

#!/bin/csh
#
#  Generate kernel database from existing kernels
kerneldbgen to='kernels.????.db' type=SPK \
            recondir='$odyssey/kernels/spk' reconfilter='m01_*.bsp' \
            lsk='$base/kernels/lsk/naif0008.tls'


This generates a file that looks like this

Code: Select all

Object = SpacecraftPosition
  RunTime = 2006-07-26T11:57:35

  Group = Dependencies
    Leapsecond Kernel = $base/kernels/lsk/naif0008.tls
  End_Group

  Group = Selection
    Time = ("2002 APR 01 00:00:00.000 TDB", "2002 JUL 01 01:00:00.000 TDB")
    File = $odyssey/kernels/spk/m01_map2.bsp
    Type = Reconstructed
  End_Group

  Group = Selection
    Time = ("2002 JUL 01 00:00:00.000 TDB", "2002 OCT 01 01:00:00.000 TDB")
    File = $odyssey/kernels/spk/m01_map3.bsp
    Type = Reconstructed
  End_Group

...........................................
 
  Group = Selection
    Time = ("2005 OCT 01 00:00:00.000 TDB", "2006 JAN 01 01:00:00.000 TDB")
    File = $odyssey/kernels/spk/m01_ext5.bsp
    Type = Reconstructed
  End_Group

  Group = Selection
    Time = ("2006 JAN 01 00:00:00.000 TDB", "2006 APR 01 01:00:00.000 TDB")
    File = $odyssey/kernels/spk/m01_ext6.bsp
    Type = Reconstructed
  End_Group
End_Object
End

There are also files with a .lbl extension that coorespond to the .bsp files that contain a lot of info.

Code: Select all

MISSION_NAME                 = "CASSINI"
SPACECRAFT_NAME              = "CASSINI"
DATA_SET_ID                  = "SPICE_SPK_FILE"
KERNEL_TYPE_ID               = "SPK"
PRODUCT_ID                   = "050825R_SCPSE_05186_05205.xsp"
PRODUCT_CREATION_TIME        = 2005-08-25T11:22:26
PRODUCER_ID                  = "CASSINI_NAV_TEAM"
MISSION_PHASE_NAME           = "TOUR"
PRODUCT_VERSION_TYPE         = "RECONSTRUCTION"
PLATFORM_OR_MOUNTING_NAME    = "N/A"
START_TIME                   = 2005-07-05T11:58:56
STOP_TIME                    = 2005-07-24T11:58:56
SPACECRAFT_CLOCK_START_COUNT = "N/A"
SPACECRAFT_CLOCK_STOP_COUNT  = "N/A"
TARGET_NAME                  = {
                               "CASSINI",
                               "EARTH BARYCENTER",
                               "JUPITER BARYCENTER",
                               "SATURN BARYCENTER",
                               "SUN",
                               "MOON",
                               "EARTH",
                               "MIMAS",
                               "ENCELADUS",
                               "TETHYS",
                               "DIONE",
                               "RHEA",
                               "TITAN",
                               "HYPERION",
                               "IAPETUS",
                               "PHOEBE",
                               "SATURN"
                               }
INSTRUMENT_NAME              = "N/A"
INSTRUMENT_ID                = "N/A"
SOURCE_PRODUCT_ID            = "SEE COMMENTS"
NOTE                         = "SPICE transfer format SPK file."
 
; 050825R_SCPSE_05186_05205.BSP LOG FILE
;
; Created 2005-08-25/11:22:25.00.
;
; BEGIN NIOSPK COMMANDS
 
LEAPSECONDS_FILE    = /cnav/software/internal/leapseconds.dat
SPK_FILE            = 050825R_SCPSE_05186_05205.BSP
  SPK_LOG_FILE      = 050825R_SCPSE_05186_05205.log
  INCLUDE_TEXT_FILE = 050825R_COMMENT_05186_05205.TXT
  SOURCE_NIO_FILE   = 050825R_SK_05186_05205.NIO
    BODIES          = -82
    BEGIN_TIME      = CAL-ET 2005 JUL 05 12:00:00.000
    END_TIME        = CAL-ET 2005 JUL 24 12:00:00.000
SOURCE_NIO_FILE = /cnav/OD/deliveries/reconstruction/050802_012Sa/odstuff/pe_941124-161222_050802.nio
    BODIES          = 3 5 6 10 301 399
    BEGIN_TIME      = CAL-ET 2005 JUL 05 12:00:00.000
    END_TIME        = CAL-ET 2005 JUL 24 12:00:00.000
SOURCE_NIO_FILE = /cnav/OD/deliveries/reconstruction/050802_012Sa/odstuff/se_040102-150116_050802.nio
    BEGIN_TIME      = CAL-ET 2005 JUL 05 12:00:00.000
    END_TIME        = CAL-ET 2005 JUL 24 12:00:00.000
 
; END NIOSPK COMMANDS
 
FILENAME:  050825R_SCPSE_05186_05205.XSP

................................
 

 
 

A couple of questions.
Is Spice going to be supported in Linux verions of Celestia too? I have a data library for ISIS3 that is about 12 GB and it primarily contains Spice kernels.
How was the win32 include and lib folders created for Spice?
What would be needed for linux verions? "SpiceUsr.h"

cartrite

[t00fri]

Chris,

I now have compiled the latest CVS under windows VC.net 2003 with SPICE=enable (with spice-libs added, of course). I would appreciate if you could quote a concrete workable spacecraft.ssc entry for Cassini.

Is this about right?
Just give me a configuration that fits the mission log by +-2m

Code: Select all

"Cassini" "Sol"
{
   Class "spacecraft"
   Mesh "cassini.3ds"
   Radius 0.011

   InfoURL "http://saturn.jpl.nasa.gov/home/index.cfm"

   Beginning 2450736.893877314 # 1997 Oct 15 09:27:11

        SpiceOrbit
        {
              Kernel "cassini.spk"
              Target "Cassini"
              Origin "Sun"

              BoundingRadius 1e10
        }
 }


Anyway with this configuration 'cassini' is not known anymore in the command line. So something got to be wrong.

No idea what I am doing, really

Bye Fridger

[symaski62]

http://www.igpp.ucla.edu/cache1/COINMS_ ... L1A_05.LBL



http://www.google.com chercher " cassini.spk "

[cartrite]

I built the kde version on IA32 Suse 9.2 and a kde version on x86_64 Suse 10. The latter had problems. There was a communiation error when I tried to run it. After I rebuilt the cspice package the communication error was gone. So if you run on a 64 bit machine, you'll probally have to recompile the spice-libs.

Now, how is this supposed to work? I put Selden's spice-cassini addon in the extras folder and nothing happened. On 8/22/2005 at 8:44:43 utc the closest Cassini got to Titan was ( Win32 3797.6 km and both kde's 3797.1 km ). The same as without spice support.

cartrite

[chris]

Now, how is this supposed to work? I put Selden's spice-cassini addon in the extras folder and nothing happened. On 8/22/2005 at 8:44:43 utc the closest Cassini got to Titan was ( Win32 3797.6 km and both kde's 3797.1 km ). The same as without spice support.

In Selden's add-ons, the SPICE versions of all the objects are called Spice_<whatever> . . . Also, the time range of the add-on is only the middle of the month of July 2005.

--Chris

[cartrite]

Chris wrote:

In Selden's add-ons, the SPICE versions of all the objects are called Spice_<whatever> . . . Also, the time range of the add-on is only the middle of the month of July 2005.

I think that addon I used was the one Selden made to demonstrate a problem.
cartrite

[cartrite]

FYI,
I used the spice test addon. Win32 and Suse 9.2 versions worked but Suse 10 did not. Suse 10 is a 64 bit OS. I was able to build Celestia with spice enabled and the obj files were compiled but spice mercury and ........ were not loaded. I guess the spice libs are not compatable with a 64 bit OS.
I ran the 64 bit Celestia from the command line and this i what I got

Toolkit version: N0060

SPICE(BUG) --

This version of SPICELIB was originally packaged by NAIF for PC hardware using
LINUX with the GCC compiler. This environment has a binary file format of
LTL-IEEE; however the software is running on an environment that has a binary
file format of UNKNOWN. This is a severe problem and may be because the
software package was intended for use on a different computer system. It also
may be the result of an improper port; please contact NAIF.

A traceback follows. The name of the highest level module is first.
furnsh_c --> FURNSH --> ZZLDKER --> SPKLEF --> DAFOPR --> ZZDDHOPN --> ZZPLTCHK

[selden]

Chris just updated the cvs code with some more enhancements to Spice (orbit paths and error messages) and for depth sorting (some more flicker problems have been eliminated).

I was fascinated to see just how much the orbits of Saturn's moons vary. Here's a picture of the orbit of Mimas:



The white ball in the back represents "Spice_Mimas" (its diameter isn't right). The brown moon in front is Celestia's current version of Mimas.

p.s.
For those who want to play with it, you can use an Addon that I uploaded to display some of the earlier bugs in the display of spice objects. (They're fixed now.) It doesn't include a Titan flyby,though, sorry.

http://www.lepp.cornell.edu/~seb/celest ... assini.zip
(2MB)

[Cham]

I'm wondering how this spice thing is actually working in Celestia. Do you need an internet connection to use that feature live in Celestia ? Really, I don't understand what it is.

How is the frame rate ?

I have the feeling it's a slow process, and that it needs to be connected. Am I wrong ?

[selden]

Cham,

An active internet connection is not required. You do have to download appropriate "SPICE kernels" from NASA or ESA, or persuade Horizons to generate one for you (I haven't tried that yet). You can think of them as greatly enhanced xyz trajectories although the SSC declarations are quite different. One's included in the Addon mentioned above.

I'm seeing between 50 and 60 fps on my home system when viewing Mimas as in the picture above. Celestia's running at about 68MB, but that's just after starting Celestia by selecting a URL that goes directly to Spice_Mimas.

System:
1GB 3.4GHz P4-550, WinXP Pro SP2
128MB GF6600GT, ForceWare v91.47
Celestia from cvs

[chris]

I'm seeing between 50 and 60 fps on my home system when viewing Mimas as in the picture above. Celestia's running at about 68MB, but that's just after starting Celestia by selecting a URL that goes directly to Spice_Mimas.

Hopefully your SPICE add-on doesn't noticeably impact frame rates. Have you found that to be the case?

I'm also curious how it affects Celestia's memory footprint. If I'm doing things right, it should only grow by the size of SPICE kernel file.

--Chris

[selden]

Letting Celestia without Spice builtin run the standard start.cel and goto Earth; and then clicking on the Spice_Mimas url, Celestia on my system is 78036KB, running at 60fps.

Letting Celestia with Spice builtin run the standard start.cel and goto Earth; and then clicking on the Spice_Mimas url, Celestia on my system is 80512KB, running at 58.8 fps.

In other words, with vertical-sync enabled it's hard for me to determine just how much of a CPU hit it's taking, although it doesn't seem to be a lot.

This is with only my test Addon installed.

[chris]

Letting Celestia without Spice builtin run the standard start.cel and goto Earth; and then clicking on the Spice_Mimas url, Celestia on my system is 78036KB, running at 60fps.

Letting Celestia with Spice builtin run the standard start.cel and goto Earth; and then clicking on the Spice_Mimas url, Celestia on my system is 80512KB, running at 58.8 fps.

In other words, with vertical-sync enabled it's hard for me to determine just how much of a CPU hit it's taking, although it doesn't seem to be a lot.

Good. That's about what I'd expect to see . . . SPICE shouldn't be slow. The speed of calculating positions depends on what type of data is in the kernel. I know that Chebyshev polynomials are often used, and they can be evaluated very quickly (see the code in jpleph.cpp) Anything would be fast compared to the 1000+ term VSOP87 series for the eight major planets . . .

--Chris

[ElChristou]

Well... fatal question... Spice on osX, how to?

If all is fine, next week I'll end the new Voyager so I was thinking it would cool to implement in the ssc the Spice data...

[symaski62]

ftp://naif.jpl.nasa.gov/pub/naif/CASSINI/kernels/spk/

060919BP_SCPSE_06262_06271.bsp
060919BP_SCPSE_06262_06271.bsp.lbl
||
||
\/

C:\Program Files\Celestia\extras\spice-cassini-2006-09\
--> spice-cassini.ssc

Code: Select all

Barycenter "Spice_Sun" "Sol"
{
   Color [ 1 1 1 ]

   Radius 100000


   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "0"
                Origin "10" 

      BoundingRadius 1e10
   }


}

Barycenter "Spice_Earth_Barycenter" "Sol/Spice_Sun"
{
   Color [1 1 1]
   Radius 100

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "3"
                Origin "0" 

      BoundingRadius 1e10
   }


}

"Spice_Earth" "Sol/Spice_Sun/Spice_Earth_Barycenter"
{
   Color [0 1 0]
   Radius 7000

   OrbitReferencePlane "ecliptic"
   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "399"
                Origin "3" 

      BoundingRadius 1e10
   }


}


"Spice_Moon" "Sol/Spice_Sun/Spice_Earth_Barycenter"
{
   Color [0 1 0]
   Radius 2000

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "301"
                Origin "3" 

      BoundingRadius 1e10
   }


}


"Spice_Saturn_Barycenter" "Sol/Spice_Sun"
{
   Color [1 1 1]
   Radius 100

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "6"
                Origin "0" 

      BoundingRadius 1e10
   }


}

"Spice_Saturn" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 0]

   Radius 80000

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "699"
                Origin "6" 

      BoundingRadius 1e10
   }
}



"Spice_Cassini" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "-82"
                Origin "6"

      BoundingRadius 1e10
   }


}



"Spice_Mimas" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "601"
                Origin "6" 

      BoundingRadius 1e10
   }


}



"Spice_Enceladus" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "602"
                Origin "6" 

      BoundingRadius 1e10
   }


}

"Spice_Tethys" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "603"
                Origin "6" 

      BoundingRadius 1e10
   }


}


"Spice_Dione" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "604"
                Origin "6" 

      BoundingRadius 1e10
   }


}


"Spice_Rhea" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "605"
                Origin "6" 

      BoundingRadius 1e10
   }


}

"Spice_Titan" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 0 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "606"
                Origin "6" 

      BoundingRadius 1e10
   }


}

"Spice_Hyperion" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "607"
                Origin "6" 

      BoundingRadius 1e10
   }


}



"Spice_Iapetus" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "608"
                Origin "6" 

      BoundingRadius 1e10
   }


}


"Spice_Phoebe" "Sol/Spice_Sun/Spice_Saturn_Barycenter"
{
   Color [1 1 1]
   Radius 100

   OrbitReferencePlane "ecliptic"

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "609"
                Origin "6" 

      BoundingRadius 1e10
   }


}


"Spice_Jupiter" "Sol/Spice_Sun"
{
   Color [0 1 1]
   Radius 100000

   SpiceOrbit
   {
      Kernel "060919BP_SCPSE_06262_06271.bsp"
               Target "5"
                Origin "0" 

      BoundingRadius 1e10
   }


}

C:\Program Files\Celestia\extras\spice-cassini-2006-09\data
--> 060919BP_SCPSE_06262_06271.bsp
--> 060919BP_SCPSE_06262_06271.bsp.lbl



voila