[Spice_discussion] spkezr vs Geocentric Solar Ecliptic (GSE) Frame

[William Thompson]

The STEREO project has been using a different definition for GSE.  I'll have to 
take a look at how all these frames differ.  The definition below is in the file

http://sohowww.nascom.nasa.gov/solarsoft/stereo/gen/data/spice/gen/heliospheric.tf

Bill Thompson


\begindata

         FRAME_GSE                    =  1803311
         FRAME_1803311_NAME           = 'GSE'
         FRAME_1803311_CLASS          =  5
         FRAME_1803311_CLASS_ID       =  1803311
         FRAME_1803311_CENTER         =  399
         FRAME_1803311_RELATIVE       = 'J2000'
         FRAME_1803311_DEF_STYLE      = 'PARAMETERIZED'
         FRAME_1803311_FAMILY         = 'TWO-VECTOR'
         FRAME_1803311_PRI_AXIS       = 'X'
         FRAME_1803311_PRI_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
         FRAME_1803311_PRI_OBSERVER   = 'EARTH'
         FRAME_1803311_PRI_TARGET     = 'SUN'
         FRAME_1803311_PRI_ABCORR     = 'NONE'
         FRAME_1803311_SEC_AXIS       = 'Z'
         FRAME_1803311_SEC_VECTOR_DEF = 'CONSTANT'
         FRAME_1803311_SEC_FRAME      = 'ECLIPDATE'
         FRAME_1803311_SEC_SPEC       = 'RECTANGULAR'
         FRAME_1803311_SEC_VECTOR     = ( 0, 0, 1 )

\begintext


On 01/29/16 10:24, William T Bridgman wrote:
> A tf file for the Van Allen probes has a different definition to build GSE:
>
>        \begindata
>
>        FRAME_GSE                    = -362930
>        FRAME_-362930_NAME           = 'GSE'
>        FRAME_-362930_CLASS          = 5
>        FRAME_-362930_CLASS_ID       = -362930
>        FRAME_-362930_CENTER         = 399
>        FRAME_-362930_RELATIVE       = 'J2000'
>        FRAME_-362930_DEF_STYLE      = 'PARAMETERIZED'
>        FRAME_-362930_FAMILY         = 'TWO-VECTOR'
>        FRAME_-362930_PRI_AXIS       = 'X'
>        FRAME_-362930_PRI_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
>        FRAME_-362930_PRI_OBSERVER   = 'EARTH'
>        FRAME_-362930_PRI_TARGET     = 'SUN'
>        FRAME_-362930_PRI_ABCORR     = 'NONE'
>        FRAME_-362930_SEC_AXIS       = 'Z'
>        FRAME_-362930_SEC_VECTOR_DEF = 'CONSTANT'
>        FRAME_-362930_SEC_SPEC       = 'RECTANGULAR'
>        FRAME_-362930_SEC_FRAME      = 'MEAN_ECLIP'
>        FRAME_-362930_SEC_VECTOR     = (0, 0, 1)
>
>        \begintext
>
> It defines the secondary as z-axis rather than y-axis.  I suspect your y-axis is
> not quite perpendicular to your x-axis which might be projecting some velocity
> in the x-direction.
>
> Tom
>
> On 1/27/16 7:33 PM, Donald F. Linton wrote:
>> I implemented the Geocentric Solar Ecliptic (GSE) Frame in the Frames
>> <http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/frames.html#Specifying
>>
>> a New Frame> reference:
>>
>> \begindata
>>     FRAME_GSE                       =  314101
>>     FRAME_314101_NAME           = 'GSE'
>>     FRAME_314101_CLASS          =  5
>>     FRAME_314101_CLASS_ID       =  314101
>>     FRAME_314101_CENTER         =  399
>>     FRAME_314101_RELATIVE       = 'J2000'
>>     FRAME_314101_DEF_STYLE      = 'PARAMETERIZED'
>>     FRAME_314101_FAMILY         = 'TWO-VECTOR'
>>     FRAME_314101_PRI_AXIS       = 'X'
>>     FRAME_314101_PRI_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
>>     FRAME_314101_PRI_OBSERVER   = 'EARTH'
>>     FRAME_314101_PRI_TARGET     = 'SUN'
>>     FRAME_314101_PRI_ABCORR     = 'NONE'
>>     FRAME_314101_SEC_AXIS       = 'Y'
>>     FRAME_314101_SEC_VECTOR_DEF = 'OBSERVER_TARGET_VELOCITY'
>>     FRAME_314101_SEC_OBSERVER   = 'EARTH'
>>     FRAME_314101_SEC_TARGET     = 'SUN'
>>     FRAME_314101_SEC_ABCORR     = 'NONE'
>>     FRAME_314101_SEC_FRAME      = 'J2000'
>> \begintext
>>
>> Using the epoch: 2017-07-01T00:00:00
>> et = 5.521392681841135e8
>>
>> sv = spkezr( "SUN", et, "J2000", "NONE", "EARTH" )
>>
>>   -2.41323e7  1.37774e8  5.97261e7  -28.9257  -4.24521  -1.83927
>>
>> then
>>
>> M = sxform("J2000", "GSE", et )
>>
>>   -0.158671     0.905874      0.392703     0.0          0.0        0.0
>>   -0.987331    -0.145594     -0.0630798    0.0          0.0        0.0
>>    3.26993e-5  -0.397737      0.9175       0.0          0.0        0.0
>>   -1.90166e-7  -2.80422e-8   -1.21495e-8  -0.158671     0.905874   0.392703
>>    3.0561e-8   -1.7445e-7    -7.56986e-8  -0.987331    -0.145594  -0.0630798
>>   -6.6631e-11  -9.82553e-12  -4.257e-12    3.26993e-5  -0.397737   0.9175
>>
>> M*SV yields
>>
>>   1.5209e8
>>   2.79397e-9
>>   7.45058e-9
>>   0.0217735
>>   6.64746e-15
>>   2.22045e-16
>>
>> I don't understand why I see 21.77 m/s of sunward velocity
>>
>>
>>
>>
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>>
>

-- 
William Thompson
NASA Goddard Space Flight Center
Code 671
Greenbelt, MD  20771
USA

301-286-2040
William.T.Thompson at nasa.gov