[Spice_discussion] spkezr vs Geocentric Solar Ecliptic (GSE) Frame
William T Bridgman
william.t.bridgman at nasa.gov
Fri Jan 29 11:22:03 PST 2016
I think the confusion is that MEAN_ECLIP (mean Ecliptic?) and ECLIPDATE
(Ecliptic of date?) can be interpreted as very slightly different systems.
Both frame definitions define the family as
MEAN_ECLIPTIC_AND_EQUINOX_OF_DATE but I'm not sure what that
significance might be.
https://en.wikipedia.org/wiki/Ecliptic_coordinate_system
Suggests the proper term might be Mean Equinox of date and that "mean
ecliptic" might not be meaningful.
Tom
On 1/29/16 1:58 PM, William Thompson wrote:
> Okay, so STEREO and Van Allen are using the exact same definition of
> GSE, that's good.
>
> On 01/29/16 12:06, Stephens, Grant K. wrote:
>> Bill,
>>
>> Van Allen Probes defines the MEAN_ECLIP frame as follows, which looks the
>> same as the ECLIPDATE frame.
>>
>>
>> \begindata
>>
>> FRAME_MEAN_ECLIP = -362913
>> FRAME_-362913_NAME = 'MEAN_ECLIP'
>> FRAME_-362913_CLASS = 5
>> FRAME_-362913_CLASS_ID = -362913
>> FRAME_-362913_CENTER = 399
>> FRAME_-362913_RELATIVE = 'J2000'
>> FRAME_-362913_DEF_STYLE = 'PARAMETERIZED'
>> FRAME_-362913_FAMILY =
>> 'MEAN_ECLIPTIC_AND_EQUINOX_OF_DATE'
>> FRAME_-362913_PREC_MODEL = 'EARTH_IAU_1976'
>> FRAME_-362913_OBLIQ_MODEL = 'EARTH_IAU_1980'
>> FRAME_-362913_ROTATION_STATE = 'ROTATING'
>>
>> \begintext
>>
>>
>>
>> Grant
>>
>> On 1/29/16 11:51 AM, "spice_discussion-bounces at naif.jpl.nasa.gov on
>> behalf
>> of William Thompson" <spice_discussion-bounces at naif.jpl.nasa.gov on
>> behalf
>> of William.T.Thompson at nasa.gov> wrote:
>>
>>> I tried using these three different definitions of GSE in SPKEZR.
>>> When I
>>> put
>>> Earth in for both the target and the observing body, I get all zeros for
>>> all
>>> three definitions, as you would expect. When I then try to put in a
>>> different
>>> body than Earth for the target, I get an error message for the Van Allen
>>> definition:
>>>
>>> % CSPICE_SPKEZR: SPICE(NOTRANSLATION):
>>> [spkezr_c->SPKEZR->SPKEZ->SPKGEO->FRMCHG->FRMGET->ZZDYNFRM->ZZDYNFID]
>>> The
>>> kernel
>>> variable FRAME_-362930_SEC_FRAME used to define frame
>>> BRIDGMAN is assigned the character value MEAN_ECLIP.
>>> This value was expected to be a reference frame
>>> name,
>>> but
>>> NAMFRM cannot translate this name to a frame ID
>>> code.
>>> % Execution halted at: $MAIN$
>>>
>>> (I renamed GSE to BRIDGMAN or LINTON to allow all three definitions
>>> to be
>>> loaded
>>> simultaneously.) The Van Allen definition must include a definition for
>>> MEAN_ECLIP frame. However, the same is true of the STEREO definition,
>>> which
>>> includes a reference to the ECLIPDATE frame defined below:
>>>
>>> \begindata
>>>
>>> FRAME_ECLIPDATE = 1803321
>>> FRAME_1803321_NAME = 'ECLIPDATE'
>>> FRAME_1803321_CLASS = 5
>>> FRAME_1803321_CLASS_ID = 1803321
>>> FRAME_1803321_CENTER = 399
>>> FRAME_1803321_RELATIVE = 'J2000'
>>> FRAME_1803321_DEF_STYLE = 'PARAMETERIZED'
>>> FRAME_1803321_FAMILY =
>>> 'MEAN_ECLIPTIC_AND_EQUINOX_OF_DATE'
>>> FRAME_1803321_PREC_MODEL = 'EARTH_IAU_1976'
>>> FRAME_1803321_OBLIQ_MODEL = 'EARTH_IAU_1980'
>>> FRAME_1803321_ROTATION_STATE = 'ROTATING'
>>>
>>> \begintext
>>>
>>> It's possible this is the same as MEAN_ECLIP in the Van Allen
>>> definition.
>>> I
>>> realize now that everything else in the STEREO and Van Allen definitions
>>> of GSE
>>> is the same.
>>>
>>> When I apply the Linton and STEREO definitions of GSE to Mars for the ET
>>> value
>>> in the original mail message, I get the following values:
>>>
>>> STEREO definition:
>>> 3.8803534e+08 54357681. 6945416.9 6.9416565
>>> -23.066438 0.37886396
>>>
>>> Linton definition:
>>> 3.8803534e+08 54357885. 6943816.8 6.9416565
>>> -23.066896 0.38321554
>>>
>>> Difference:
>>> 0.0000000 -204.42863 1600.1297 0.0000000
>>> 0.00045798140 -0.0043515797
>>>
>>> The light travel times are the same for both definitions.
>>>
>>> Bill Thompson
>>>
>>>
>>> On 01/29/16 11:17, 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/helios
>>>>
>>>> pheric.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
>>>>>>
>>>>>
>>>>
>>>
>>> --
>>> William Thompson
>>> NASA Goddard Space Flight Center
>>> Code 671
>>> Greenbelt, MD 20771
>>> USA
>>>
>>> 301-286-2040
>>> William.T.Thompson at nasa.gov
>>> _______________________________________________
>>> 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/
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