[Spice_discussion] spkezr vs Geocentric Solar Ecliptic (GSE) Frame
William Thompson
William.T.Thompson at nasa.gov
Fri Jan 29 08:51:49 PST 2016
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/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
>>>
>>
>
--
William Thompson
NASA Goddard Space Flight Center
Code 671
Greenbelt, MD 20771
USA
301-286-2040
William.T.Thompson at nasa.gov
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