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

[William T Bridgman]

I was just discussing this question of mean ecliptic vs ecliptic of date 
with Ernie Wright.  Might be a good idea to nail this down consistently.

Thanks,
Tom

On 1/29/16 11:17 AM, William Thompson wrote:
> 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
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Spice_discussion mailing list
>>> Spice_discussion at naif.jpl.nasa.gov
>>> https://naif.jpl.nasa.gov/mailman/listinfo/spice_discussion
>>>
>>
>

-- 
Dr. William T."Tom" Bridgman               Scientific Visualization Studio
Global Science & Technology, Inc.          NASA/Goddard Space Flight Center
Email: William.T.Bridgman at nasa.gov         Code 606.4
Phone: 301-286-1346                        Greenbelt, MD 20771
FAX:   301-286-1634                        http://svs.gsfc.nasa.gov/