[Spice_discussion]
Dynamic frames for heliospheric coordinate systems
William Thompson
William.T.Thompson.1 at gsfc.nasa.gov
Wed Feb 23 07:08:47 PST 2005
Folks:
With the introduction of dynamic frames in version N0058 of the SPICE toolkit,
I've been looking into how to use this to implement various standard
heliospheric coordinate systems for the upcoming STEREO mission. Since these
coordinate systems are applicable to any heliospheric mission, I decided to
share these definitions. The attached text frame kernel allows one to derive
coordinates in:
HAE_D Heliospheric Aries Ecliptic (of date)
GSE Geocentric Solar Ecliptic
HCI Heliocentric Inertial
HEE Heliocentric Earth Ecliptic
HEEQ Heliocentric Earth Equatorial
Note that the definition of GSE is somewhat different than the example given in
the SPICE documentation. In the example, Earth's velocity vector is used as a
proxy to determine the ecliptic plane, while here the ecliptic plane of date is
determined using an intermediate dynamic frame. This second approach should be
more accurate, with only a slightly higher (~20%) computational cost.
Many other standard heliospheric coordinate systems can be realized natively
within SPICE, such as HAE_J2000, Geocentric Equatorial Inertial (GEI),
Geographic (GEO), and Carrington Heliographic.
I'd like to end by thanking the SPICE team for introducing dynamic frames. It
makes implementation of these standard frames much easier.
--
William Thompson
NASA Goddard Space Flight Center
Code 612.1
Greenbelt, MD 20771
USA
301-286-2040
William.T.Thompson.1 at gsfc.nasa.gov
-------------- next part --------------
Dynamic Heliospheric Coordinate Frames developed for the NASA STEREO mission
The coordinate frames in this file all have ID values based on the pattern
18ccple, where
18 = Prefix to put in the allowed 1400000 to 2000000 range
cc = 03 for geocentric, 10 for heliocentric
p = Pole basis: 1=geographic, 2=geomagnetic, 3=ecliptic, 4=solar
l = Longitude basis: 1=Earth-Sun, 2=ecliptic
e = Ecliptic basis: 0=J2000, 1=mean, 2=true
Author: William Thompson
NASA Goddard Space Flight Center
Code 612.1
Greenbelt, MD 20771
William.T.Thompson.1 at gsfc.nasa.gov
History
Version 1, 18-Feb-2005, WTT, initial release
GSE and ECLIPDATE definitions from examples in frames.req by C.H. Acton
HEE definition is based on the GSE example
Version 2, 22-Feb-2005, WTT
Modified HCI definition to tie to IAU_SUN frame
Use RECTANGULAR specification in HEEQ frame
Version 3, 23-Feb-2005, WTT
Correct GSE and HEE definitions to use ECLIPDATE axis
Mean Ecliptic of Date (ECLIPDATE) Frame
Definition of the Mean Ecliptic of Date frame:
All vectors are geometric: no aberration corrections are
used.
The X axis is the first point in Aries for the mean ecliptic of
date, and the Z axis points along the ecliptic north pole.
The Y axis is Z cross X, completing the right-handed
reference frame.
This reference frame can be used to realize the HAE coordinate
system by using the sun as the observing body.
\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
Geocentric Solar Ecliptic (GSE) Frame
Definition of the Geocentric Solar Ecliptic frame:
All vectors are geometric: no aberration corrections are
used.
The position of the sun relative to the earth is the primary
vector: the X axis points from the earth to the sun.
The northern surface normal to the mean ecliptic of date is the
secondary vector: the Z axis is the component of this vector
orthogonal to the X axis.
The Y axis is Z cross X, completing the right-handed
reference frame.
\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
Heliocentric Inertial (HCI) Frame
Definition of the Heliocentric Inertial frame:
All vectors are geometric: no aberration corrections are
used.
The solar rotation axis is the primary vector: the Z axis points
in the solar north direction.
The solar ascending node on the ecliptic of J2000 forms the X
axis.
The Y axis is Z cross X, completing the right-handed
reference frame.
\begindata
FRAME_HCI = 1810420
FRAME_1810420_NAME = 'HCI'
FRAME_1810420_CLASS = 5
FRAME_1810420_CLASS_ID = 1810420
FRAME_1810420_CENTER = 10
FRAME_1810420_RELATIVE = 'J2000'
FRAME_1810420_DEF_STYLE = 'PARAMETERIZED'
FRAME_1810420_FAMILY = 'TWO-VECTOR'
FRAME_1810420_PRI_AXIS = 'Z'
FRAME_1810420_PRI_VECTOR_DEF = 'CONSTANT'
FRAME_1810420_PRI_FRAME = 'IAU_SUN'
FRAME_1810420_PRI_SPEC = 'RECTANGULAR'
FRAME_1810420_PRI_VECTOR = ( 0, 0, 1 )
FRAME_1810420_SEC_AXIS = 'Y'
FRAME_1810420_SEC_VECTOR_DEF = 'CONSTANT'
FRAME_1810420_SEC_FRAME = 'ECLIPJ2000'
FRAME_1810420_SEC_SPEC = 'RECTANGULAR'
FRAME_1810420_SEC_VECTOR = ( 0, 0, 1 )
\begintext
Heliocentric Earth Ecliptic (HEE) Frame
Definition of the Heliocentric Earth Ecliptic frame:
All vectors are geometric: no aberration corrections are
used.
The position of the earth relative to the sun is the primary
vector: the X axis points from the sun to the earth.
The northern surface normal to the mean ecliptic of date is the
secondary vector: the Z axis is the component of this vector
orthogonal to the X axis.
The Y axis is Z cross X, completing the right-handed
reference frame.
\begindata
FRAME_HEE = 1810311
FRAME_1810311_NAME = 'HEE'
FRAME_1810311_CLASS = 5
FRAME_1810311_CLASS_ID = 1810311
FRAME_1810311_CENTER = 10
FRAME_1810311_RELATIVE = 'J2000'
FRAME_1810311_DEF_STYLE = 'PARAMETERIZED'
FRAME_1810311_FAMILY = 'TWO-VECTOR'
FRAME_1810311_PRI_AXIS = 'X'
FRAME_1810311_PRI_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
FRAME_1810311_PRI_OBSERVER = 'SUN'
FRAME_1810311_PRI_TARGET = 'EARTH'
FRAME_1810311_PRI_ABCORR = 'NONE'
FRAME_1810311_SEC_AXIS = 'Z'
FRAME_1810311_SEC_VECTOR_DEF = 'CONSTANT'
FRAME_1810311_SEC_FRAME = 'ECLIPDATE'
FRAME_1810311_SEC_SPEC = 'RECTANGULAR'
FRAME_1810311_SEC_VECTOR = ( 0, 0, 1 )
\begintext
Heliocentric Earth Equatorial (HEEQ) Frame
Definition of the Heliocentric Earth Equatorial frame:
All vectors are geometric: no aberration corrections are
used.
The solar rotation axis is the primary vector: the Z axis points
in the solar north direction.
The position of the sun relative to the earth is the secondary
vector: the X axis is the component of this position vector
orthogonal to the Z axis.
The Y axis is Z cross X, completing the right-handed
reference frame.
\begindata
FRAME_HEEQ = 1810411
FRAME_1810411_NAME = 'HEEQ'
FRAME_1810411_CLASS = 5
FRAME_1810411_CLASS_ID = 1810411
FRAME_1810411_CENTER = 10
FRAME_1810411_RELATIVE = 'J2000'
FRAME_1810411_DEF_STYLE = 'PARAMETERIZED'
FRAME_1810411_FAMILY = 'TWO-VECTOR'
FRAME_1810411_PRI_AXIS = 'Z'
FRAME_1810411_PRI_VECTOR_DEF = 'CONSTANT'
FRAME_1810411_PRI_FRAME = 'IAU_SUN'
FRAME_1810411_PRI_SPEC = 'RECTANGULAR'
FRAME_1810411_PRI_VECTOR = ( 0, 0, 1 )
FRAME_1810411_SEC_AXIS = 'X'
FRAME_1810411_SEC_VECTOR_DEF = 'OBSERVER_TARGET_POSITION'
FRAME_1810411_SEC_OBSERVER = 'SUN'
FRAME_1810411_SEC_TARGET = 'EARTH'
FRAME_1810411_SEC_ABCORR = 'NONE'
FRAME_1810411_SEC_FRAME = 'IAU_SUN'
\begintext
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