Table of contents
CSPICE_GFILUM determines the time intervals over which a specified
constraint on the observed phase, solar incidence, or emission angle
at a specified target body surface point is met.
Given:
method name specifying the computation method to use.
[1,c1] = size(method); char = class(method)
or
[1,1] = size(method); cell = class(method)
Parameters include, but are not limited to, the shape model
used to represent the surface of the target body.
The only choice currently supported is
'Ellipsoid' The illumination angle
computation uses a triaxial
ellipsoid to model the surface
of the target body. The
ellipsoid's radii must be
available in the kernel pool.
Neither case nor white space are significant in
`method'. For example, the string ' eLLipsoid ' is
valid.
angtyp name specifying the illumination angle for which a search
is to be performed.
[1,c2] = size(angtyp); char = class(angtyp)
or
[1,1] = size(angtyp); cell = class(angtyp)
The possible values of `angtyp' are:
'PHASE'
'INCIDENCE'
'EMISSION'
See the -Particulars section below for a detailed
description of these angles.
Neither case nor white space are significant in
`angtyp'. For example, the string ' Incidence ' is
valid.
target name of the target body.
[1,c3] = size(target); char = class(target)
or
[1,1] = size(target); cell = class(target)
The point at which the illumination angles are defined is
located on the surface of this body.
Optionally, you may supply the integer ID code for
the object as an integer string. For example both
'MOON' and '301' are legitimate strings that indicate
the moon is the target body.
illmn name of the illumination source.
[1,c4] = size(illmn); char = class(illmn)
or
[1,1] = size(illmn); cell = class(illmn)
This source may be any ephemeris object. Case, blanks, and
numeric values are treated in the same way as for the
input `target'.
fixref name of the body-fixed, body-centered reference frame
associated with the target body.
[1,c5] = size(fixref); char = class(fixref)
or
[1,1] = size(fixref); cell = class(fixref)
The input surface point `spoint' is expressed relative to
this reference frame, and this frame is used to
define the orientation of the target body as a
function of time.
The string `fixref' is case-insensitive, and leading
and trailing blanks in `fixref' are not significant.
abcorr describes the aberration corrections to apply to the state
evaluations to account for one-way light time and stellar
aberration.
[1,c6] = size(abcorr); char = class(abcorr)
or
[1,1] = size(abcorr); cell = class(abcorr)
Any 'reception' correction accepted by cspice_spkezr can be
used here. See the header of cspice_spkezr for a detailed
description of the aberration correction options.
For convenience, the options are listed below:
'NONE' Apply no correction.
'LT' 'Reception' case: correct for
one-way light time using a Newtonian
formulation.
'LT+S' 'Reception' case: correct for
one-way light time and stellar
aberration using a Newtonian
formulation.
'CN' 'Reception' case: converged
Newtonian light time correction.
'CN+S' 'Reception' case: converged
Newtonian light time and stellar
aberration corrections.
Case and blanks are not significant in the string
`abcorr'.
obsrvr name of the observing body.
[1,c7] = size(obsrvr); char = class(obsrvr)
or
[1,1] = size(obsrvr); cell = class(obsrvr)
Optionally, you may supply the ID code of the object as an
integer string. For example, both 'EARTH' and '399' are
legitimate strings to supply to indicate that the
observer is Earth.
spoint a surface point on the target body, expressed in
Cartesian coordinates, relative to the body-fixed
target frame designated by `fixref'.
[3,1] = size(spoint); double = class(spoint)
`spoint' need not be visible from the observer's
location in order for the constraint specified by
`relate' and `refval' (see descriptions below) to be
satisfied.
The components of `spoint' have units of km.
relate describes the constraint relational operator on a specified
illumination angle.
[1,c8] = size(relate); char = class(relate)
or
[1,1] = size(relate); cell = class(relate)
The result window found by this routine indicates the time
intervals where the constraint is satisfied.
Supported values of `relate' and corresponding meanings
are shown below:
'>' The angle is greater than the reference
value `refval'.
'=' The angle is equal to the reference
value `refval'.
'<' The angle is less than the reference
value `refval'.
'ABSMAX' The angle is at an absolute maximum.
'ABSMIN' The angle is at an absolute minimum.
'LOCMAX' The angle is at a local maximum.
'LOCMIN' The angle is at a local minimum.
The caller may indicate that the region of interest is
the set of time intervals where the angle is within a
specified separation from an absolute extremum. The
argument `adjust' (described below) is used to specify
this separation.
Local extrema are considered to exist only in the
interiors of the intervals comprising the confinement
window: a local extremum cannot exist at a boundary
point of the confinement window.
Case is not significant in the string `relate'.
refval reference value used together with the argument
`relate' to define an equality or inequality to be
satisfied by the specified illumination angle.
[1,1] = size(refval); double = class(refval)
See the discussion of `relate' above for further information.
The units of `refval' are radians.
adjust parameter used to modify searches for absolute extrema.
[1,1] = size(adjust); double = class(adjust)
When `relate' is set to 'ABSMAX' or 'ABSMIN' and `adjust'
is set to a positive value, cspice_gfilum will find times
when the observer-target distance is within `adjust' km of
the specified extreme value.
If `adjust' is non-zero and a search for an absolute
minimum `min' is performed, the result window contains
time intervals when the observer-target distance has
values between `min' and min+adjust.
If the search is for an absolute maximum `max', the
corresponding range is from max-adjust to `max'.
`adjust' is not used for searches for local extrema,
equality or inequality conditions.
step step size to use in the search.
[1,1] = size(step); double = class(step)
`step' must be short enough for a search using this step
size to locate the time intervals where the specified
illumination angle is monotone increasing or
decreasing. However, `step' must not be *too* short, or
the search will take an unreasonable amount of time.
The choice of `step' affects the completeness but not
the precision of solutions found by this routine; the
precision is controlled by the convergence tolerance.
See the discussion of the parameter SPICE_GF_CNVTOL for
details.
`step' has units of seconds.
nintvls a parameter specifying the number of intervals that
can be accommodated by each of the dynamically allocated
workspace windows used internally by this routine.
[1,1] = size(nintvls); int32 = class(nintvls)
In many cases, it's not necessary to compute an accurate
estimate of how many intervals are needed; rather, the
user can pick a size considerably larger than what's
really required.
However, since excessively large arrays can prevent
applications from compiling, linking, or running
properly, sometimes `nintvls' must be set according to
the actual workspace requirement. A rule of thumb for
the number of intervals needed is
nintvls = 2*n + ( m / step )
where
n is the number of intervals in the confinement
window
m is the measure of the confinement window, in
units of seconds
step is the search step size in seconds
cnfine a SPICE window that confines the time period over
which the specified search is conducted.
[2r,1] = size(cnfine); double = class(cnfine)
`cnfine' may consist of a single interval or a collection of
intervals.
The endpoints of the time intervals comprising `cnfine'
are interpreted as seconds past J2000 TDB.
See the -Examples section below for a code example that
shows how to create a confinement window.
In some cases the observer's state may be computed at
times outside of `cnfine' by as much as 2 seconds. See
-Particulars for details.
the call:
[result] = cspice_gfilum( method, angtyp, target, illmn, fixref, ...
abcorr, obsrvr, spoint, relate, refval, ...
adjust, step, nintvls, cnfine )
returns:
result the SPICE window of intervals, contained within the
confinement window `cnfine', on which the specified
constraint is satisfied.
[2s,1] = size(result); double = class(result)
If the search is for local extrema, or for absolute
extrema with `adjust' set to zero, then normally each
interval of `result' will be a singleton: the left and
right endpoints of each interval will be identical.
If no times within the confinement window satisfy the
constraint, `result' will return with cardinality zero.
All parameters described here are declared in the Mice include file
MiceGF.m. See that file for parameter values.
SPICE_GF_CNVTOL
is the convergence tolerance used for finding
endpoints of the intervals comprising the result
window. SPICE_GF_CNVTOL is used to determine when
binary searches for roots should terminate: when a
root is bracketed within an interval of length
SPICE_GF_CNVTOL, the root is considered to have
been found.
The accuracy, as opposed to precision, of roots found
by this routine depends on the accuracy of the input
data. In most cases, the accuracy of solutions will be
inferior to their precision.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
1) Determine time intervals over which the planned Mars Science
Laboratory (MSL) Gale Crater landing site satisfies certain
constraints on its illumination and visibility as seen from
the Mars Reconnaissance Orbiter (MRO) spacecraft. The
observation period will range from slightly before the planned
landing time to about 10 days later.
In this case we require the emission angle to be less than
30 degrees and the solar incidence angle to be less than
40 degrees.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: gfilum_ex1.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de421.bsp Planetary ephemeris
pck00010.tpc Planet orientation
and radii
naif0012.tls Leapseconds
mro_psp24.bsp MRO ephemeris
\begindata
KERNELS_TO_LOAD = ( 'de421.bsp',
'pck00010.tpc',
'naif0012.tls',
'mro_psp24.bsp' )
\begintext
End of meta-kernel
Example code begins here.
function gfilum_ex1()
%
% Output time format:
%
TIMFMT = 'YYYY MON DD HR:MN:SC.###### TDB::TDB';
%
% Meta-kernel name:
%
META = 'gfilum_ex1.tm';
%
% Maximum number of intervals in the windows
% used in this program:
%
MAXIVL = 1000;
%
% Local variables
%
r2d = cspice_dpr();
%
% Initial values
%
% Mars planetodetic coordinates of landing site.
% Angular units are degrees; distance units are km.
%
gclat = -4.543182;
gclon = 137.420000;
gcalt = -4.876405;
%
% Load kernels:
%
cspice_furnsh( META );
%
% Convert the landing site location from planetodetic
% to Cartesian coordinates for use with GFILUM.
%
radii = cspice_bodvrd( 'MARS', 'RADII', 3 );
re = radii(1);
rp = radii(3);
f = ( re - rp ) / re;
gcpos = cspice_georec( gclon * cspice_rpd(), ...
gclat * cspice_rpd(), ...
gcalt, re, f);
%
% Set the search interval:
%
utcbeg = '2012 AUG 5 00:00:00 UTC';
et0 = cspice_str2et( utcbeg );
utcend = '2012 SEP 15 00:00:00 UTC';
et1 = cspice_str2et( utcend );
cnfine = cspice_wninsd( et0, et1 );
%
% Set observer, target, aberration correction, and the
% Mars body-fixed, body-centered reference frame. The
% lighting source is the sun.
%
% Aberration corrections are set for remote observations.
%
illmn = 'sun';
obsrvr = 'mro';
target = 'mars';
abcorr = 'cn+s';
fixref = 'iau_mars';
%
% Initialize the adjustment value for absolute
% extremum searches. We're not performing
% such searches in this example, but this input
% to GFILUM must still be set.
%
adjust = 0.0;
%
% The computation uses an ellipsoidal model for the
% target body shape.
%
method = 'Ellipsoid';
%
% Set the reference value to use for the solar
% incidence angle search.
%
refval = 45.0 * cspice_rpd();
%
% Since the period of the solar incidence angle
% is about one Martian day, we can safely use 6 hours
% as the search step.
%
step = 21600.0;
%
% Search over the confinement window for times
% when the solar incidence angle is less than
% the reference value.
%
[wnsolr] = cspice_gfilum( method, 'INCIDENCE', target, ...
illmn, fixref, abcorr, ...
obsrvr, gcpos, '<', ...
refval, adjust, step, ...
MAXIVL, cnfine );
%
% With the search on the incidence angle complete, perform
% a search on the emission angle.
%
% Set the reference value for the emission angle search.
%
refval = 80.0 * cspice_rpd();
%
% We'll use 15 minutes as the search step. This step
% is small enough to be suitable for Mars orbiters.
% Units are seconds.
%
step = 900.0;
%
% Search over the previous result window for times when the
% emission angle is less than the reference value.
%
[result] = cspice_gfilum( method, 'EMISSION', target, illmn, ...
fixref, abcorr, obsrvr, gcpos, ...
'<', refval, adjust, step, ...
MAXIVL, wnsolr );
%
% Display the result window. Show the solar incidence
% and emission angles at the window's interval
% boundaries.
%
if ( cspice_wncard( result ) == 0 )
disp( ' Window is empty: condition is not met.' )
else
fprintf( ' ' )
fprintf( ' Solar Incidence Emission\n' )
fprintf( ' ' )
fprintf( ' (deg) (deg)\n\n' )
for i=1:cspice_wncard( result )
[start, finish] = cspice_wnfetd( result, i );
%
% Compute the angles of interest at the boundary
% epochs.
%
timstr = cspice_timout( start, TIMFMT );
[trgepc, srfvec, phase, solar, emissn] = ...
cspice_ilumin( method, target, ...
start, fixref, ...
abcorr, obsrvr, ...
gcpos );
fprintf ( ' Start: %s %14.9f %14.9f\n', timstr, ...
solar*r2d, ...
emissn*r2d )
timstr = cspice_timout( finish, TIMFMT);
[trgepc, srfvec, phase, solar, emissn] = ...
cspice_ilumin( method, target, ...
finish, fixref, ...
abcorr, obsrvr, ...
gcpos );
fprintf ( ' Start: %s %14.9f %14.9f\n\n', timstr, ...
solar*r2d, ...
emissn*r2d )
end
end
%
% It's always good form to unload kernels after use,
% particularly in MATLAB due to data persistence.
%
cspice_kclear
When this program was executed on a Mac/Intel/Octave6.x/64-bit
platform, the output was:
Solar Incidence Emission
(deg) (deg)
Start: 2012 AUG 09 06:14:46.475539 TDB 41.793493032 80.000000000
Start: 2012 AUG 09 06:15:29.695045 TDB 41.954623385 80.000000002
Start: 2012 AUG 14 09:37:47.093234 TDB 42.772767813 80.000000007
Start: 2012 AUG 14 09:41:59.554719 TDB 43.729251675 79.999999998
Start: 2012 AUG 19 13:01:43.056249 TDB 44.000361046 80.000000017
Start: 2012 AUG 19 13:06:03.429007 TDB 44.999999999 75.754083310
Start: 2012 AUG 30 20:10:42.196910 TDB 42.214690783 79.999999993
Start: 2012 AUG 30 20:14:47.411493 TDB 43.170768309 79.999999996
Start: 2012 SEP 04 23:35:53.476437 TDB 43.804510481 79.999999983
Start: 2012 SEP 04 23:40:57.001978 TDB 45.000000001 77.221887661
Start: 2012 SEP 11 03:22:35.751759 TDB 41.115348965 80.000000009
Start: 2012 SEP 11 03:24:59.610628 TDB 41.684463728 79.999999996
This routine determines a set of one or more time intervals
within the confinement window when the specified illumination
angle satisfies a caller-specified constraint. The resulting set
of intervals is returned as a SPICE window.
The term "illumination angles" refers to the following set of
angles:
phase angle Angle between the vectors from the
surface point to the observer and
from the surface point to the
illumination source.
incidence angle Angle between the surface normal at
the specified surface point and the
vector from the surface point to the
illumination source. When the sun is
the illumination source, this angle is
commonly called the "solar incidence
angle."
emission angle Angle between the surface normal at
the specified surface point and the
vector from the surface point to the
observer.
The diagram below illustrates the geometric relationships
defining these angles. The labels for the incidence, emission,
and phase angles are "inc.", "e.", and "phase".
*
illumination source
surface normal vector
._ _.
|\ /| illumination
\ phase / source vector
\ . . /
. .
\ ___ /
. \/ \/
_\ inc./
. / \ /
. | e. \ /
* <--------------- * surface point on
viewing vector target body
location to viewing
(observer) location
Note that if the target-observer vector, the target normal vector
at the surface point, and the target-illumination source vector
are coplanar, then phase is the sum of the incidence and emission
angles. This rarely occurs; usually
phase angle < incidence angle + emission angle
All of the above angles can be computed using light time
corrections, light time and stellar aberration corrections, or no
aberration corrections. In order to describe apparent geometry as
observed by a remote sensing instrument, both light time and
stellar aberration corrections should be used.
The way aberration corrections are applied by this routine
is described below.
Light time corrections
======================
Observer-target surface point vector
------------------------------------
Let `et' be the epoch at which an observation or remote
sensing measurement is made, and let et - lt (`lt' stands
for "light time") be the epoch at which the photons
received at `et' were emitted from the surface point `spoint'.
Note that the light time between the surface point and
observer will generally differ from the light time between
the target body's center and the observer.
Target body's orientation
-------------------------
Using the definitions of `et' and `lt' above, the target body's
orientation at et - lt is used. The surface normal is
dependent on the target body's orientation, so the body's
orientation model must be evaluated for the correct epoch.
Target body -- illumination source vector
-----------------------------------------
The surface features on the target body near `spoint' will
appear in a measurement made at `et' as they were at et-lt.
In particular, lighting on the target body is dependent on
the apparent location of the illumination source as seen
from the target body at et-lt. So, a second light time
correction is used to compute the position of the
illumination source relative to the surface point.
Stellar aberration corrections
==============================
Stellar aberration corrections are applied only if
light time corrections are applied as well.
Observer-target surface point body vector
-----------------------------------------
When stellar aberration correction is performed, the
observer-to-surface point direction vector, which we'll
call SRFVEC, is adjusted so as to point to the apparent
position of `spoint': considering `spoint' to be an ephemeris
object, SRFVEC points from the observer's position at `et' to
the light time and stellar aberration
corrected position of `spoint'.
Target body-illumination source vector
--------------------------------------
The target body-illumination source vector is the apparent
position of the illumination source, corrected for light
time and stellar aberration, as seen from the surface point
`spoint' at time et-lt.
Below we discuss in greater detail aspects of this routine's
solution process that are relevant to correct and efficient
use of this routine in user applications.
The Search Process
==================
Regardless of the type of constraint selected by the caller, this
routine starts the search for solutions by determining the time
periods, within the confinement window, over which the specified
illumination angle is monotone increasing and monotone decreasing.
Each of these time periods is represented by a SPICE window.
Having found these windows, all of the illumination angle's local
extrema within the confinement window are known. Absolute extrema
then can be found very easily.
Within any interval of these "monotone" windows, there will be at
most one solution of any equality constraint. Since the boundary
of the solution set for any inequality constraint is contained in
the union of
- the set of points where an equality constraint is met
- the boundary points of the confinement window
the solutions of both equality and inequality constraints can be
found easily once the monotone windows have been found.
Step Size
=========
The monotone windows (described above) are found via a two-step
search process. Each interval of the confinement window is
searched as follows: first, the input step size is used to
determine the time separation at which the sign of the rate of
change of the illumination angle will be sampled. Starting at the
left endpoint of an interval, samples will be taken at each step.
If a change of sign is found, a root has been bracketed; at that
point, the time at which the rate of change of the selected
illumination angle is zero can be found by a refinement process,
for example, via binary search.
Note that the optimal choice of step size depends on the lengths
of the intervals over which the illumination angle is monotone:
the step size should be shorter than the shortest of these
intervals (within the confinement window).
The optimal step size is *not* necessarily related to the lengths
of the intervals comprising the result window. For example, if
the shortest monotone interval has length 10 days, and if the
shortest result window interval has length 5 minutes, a step size
of 9.9 days is still adequate to find all of the intervals in the
result window. In situations like this, the technique of using
monotone windows yields a dramatic efficiency improvement over a
state-based search that simply tests at each step whether the
specified constraint is satisfied. The latter type of search can
miss solution intervals if the step size is longer than the
shortest solution interval.
Having some knowledge of the relative geometry of the target,
observer, and illumination source can be a valuable aid in
picking a reasonable step size. In general, the user can
compensate for lack of such knowledge by picking a very short
step size; the cost is increased computation time.
Note that the step size is not related to the precision with which
the endpoints of the intervals of the result window are computed.
That precision level is controlled by the convergence tolerance.
Convergence Tolerance
=====================
As described above, the root-finding process used by this routine
involves first bracketing roots and then using a search process
to locate them. "Roots" are both times when local extrema are
attained and times when the illumination angle is equal to a
reference value. All endpoints of the intervals comprising the
result window are either endpoints of intervals of the
confinement window or roots.
Once a root has been bracketed, a refinement process is used to
narrow down the time interval within which the root must lie.
This refinement process terminates when the location of the root
has been determined to within an error margin called the
"convergence tolerance." The convergence tolerance used by this
routine is set via the parameter SPICE_GF_CNVTOL.
The value of SPICE_GF_CNVTOL is set to a "tight" value so that the
tolerance doesn't become the limiting factor in the accuracy of
solutions found by this routine. In general the accuracy of input
data will be the limiting factor.
The user may change the convergence tolerance from the default
SPICE_GF_CNVTOL value by calling the routine cspice_gfstol, e.g.
cspice_gfstol( tolerance value in seconds );
Call cspice_gfstol prior to calling this routine. All subsequent
searches will use the updated tolerance value.
Searches over time windows of long duration may require use of
larger tolerance values than the default: the tolerance must be
large enough so that it, when added to or subtracted from the
confinement window's lower and upper bounds, yields distinct time
values.
Setting the tolerance tighter than SPICE_GF_CNVTOL is unlikely to be
useful, since the results are unlikely to be more accurate.
Making the tolerance looser will speed up searches somewhat,
since a few convergence steps will be omitted.
The Confinement Window
======================
The simplest use of the confinement window is to specify a time
interval within which a solution is sought. However, the
confinement window can, in some cases, be used to make searches
more efficient. Sometimes it's possible to do an efficient search
to reduce the size of the time period over which a relatively
slow search of interest must be performed.
Certain types of searches require the state of the observer,
relative to the solar system barycenter, to be computed at times
slightly outside the confinement window `cnfine'. The time window
that is actually used is the result of "expanding" `cnfine' by a
specified amount "T": each time interval of `cnfine' is expanded by
shifting the interval's left endpoint to the left and the right
endpoint to the right by T seconds. Any overlapping intervals are
merged. (The input argument `cnfine' is not modified.)
The window expansions listed below are additive: if both
conditions apply, the window expansion amount is the sum of the
individual amounts.
- If a search uses an equality constraint, the time window
over which the state of the observer is computed is expanded
by 1 second at both ends of all of the time intervals
comprising the window over which the search is conducted.
- If a search uses stellar aberration corrections, the time
window over which the state of the observer is computed is
expanded as described above.
When light time corrections are used, expansion of the search
window also affects the set of times at which the light time-
corrected state of the target is computed.
In addition to the possible 2 second expansion of the search
window that occurs when both an equality constraint and stellar
aberration corrections are used, round-off error should be taken
into account when the need for data availability is analyzed.
1) In order for this routine to produce correct results,
the step size must be appropriate for the problem at hand.
Step sizes that are too large may cause this routine to miss
roots; step sizes that are too small may cause this routine
to run unacceptably slowly and in some cases, find spurious
roots.
This routine does not diagnose invalid step sizes, except that
if the step size is non-positive, the error SPICE(INVALIDSTEP)
is signaled by a routine in the call tree of this routine.
2) Due to numerical errors, in particular,
- Truncation error in time values
- Finite tolerance value
- Errors in computed geometric quantities
it is *normal* for the condition of interest to not always be
satisfied near the endpoints of the intervals comprising the
result window.
The result window may need to be contracted slightly by the
caller to achieve desired results. The SPICE window routine
cspice_wncond can be used to contract the result window.
3) If an error (typically cell overflow) occurs while performing
window arithmetic, the error is signaled by a routine
in the call tree of this routine.
4) If the output SPICE window `result' has insufficient capacity to
hold the set of intervals on which the specified illumination
angle condition is met, an error is signaled by a routine in
the call tree of this routine.
5) If the input target body-fixed frame `fixref' is not
recognized, an error is signaled by a routine in the call
tree of this routine. A frame name may fail to be recognized
because a required frame specification kernel has not been
loaded; another cause is a misspelling of the frame name.
6) If the input frame `fixref' is not centered at the target body,
an error is signaled by a routine in the call tree of this
routine.
7) If the input argument `method' is not recognized, an error is
signaled by a routine in the call tree of this routine.
8) If the illumination angle type `angtyp' is not recognized,
an error is signaled by a routine in the call tree
of this routine.
9) If the relational operator `relate' is not recognized, an
error is signaled by a routine in the call tree of this
routine.
10) If the aberration correction specifier contains an
unrecognized value, an error is signaled by a routine in the
call tree of this routine.
11) If `adjust' is negative, an error is signaled by a routine in
the call tree of this routine.
12) If any of the input body names do not map to NAIF ID
codes, an error is signaled by a routine in the call tree of
this routine.
13) If the target coincides with the observer or the illumination
source, an error is signaled by a routine in the call tree
of this routine.
14) If required ephemerides or other kernel data are not
available, an error is signaled by a routine in the call tree
of this routine.
15) If any of the input arguments, `method', `angtyp', `target',
`illmn', `fixref', `abcorr', `obsrvr', `spoint', `relate',
`refval', `adjust', `step', `nintvls' or `cnfine', is
undefined, an error is signaled by the Matlab error handling
system.
16) If any of the input arguments, `method', `angtyp', `target',
`illmn', `fixref', `abcorr', `obsrvr', `spoint', `relate',
`refval', `adjust', `step', `nintvls' or `cnfine', is not of
the expected type, or it does not have the expected dimensions
and size, an error is signaled by the Mice interface.
Appropriate kernels must be loaded by the calling program before
this routine is called.
The following data are required:
- SPK data: ephemeris data for target, observer, and the
illumination source must be loaded. If aberration
corrections are used, the states of target, observer, and
the illumination source relative to the solar system
barycenter must be calculable from the available ephemeris
data. Typically ephemeris data are made available by loading
one or more SPK files via cspice_furnsh.
- PCK data: if the target body shape is modeled as an
ellipsoid (currently no other shapes are supported),
triaxial radii for the target body must be loaded
into the kernel pool. Typically this is done by loading a
text PCK file via cspice_furnsh.
- Further PCK data: rotation data for the target body must be
loaded. These may be provided in a text or binary PCK file.
- Frame data: if a frame definition not built into SPICE
is required to convert the observer and target states to the
body-fixed frame of the target, that definition must be
available in the kernel pool. Typically the definition is
supplied by loading a frame kernel via cspice_furnsh.
- In some cases the observer's state may be computed at times
outside of `cnfine' by as much as 2 seconds; data required to
compute this state must be provided by loaded kernels. See
-Particulars for details.
In all cases, kernel data are normally loaded once per program
run, NOT every time this routine is called.
1) The kernel files to be used by this routine must be loaded
(normally using the Mice routine cspice_furnsh) before this
routine is called.
2) This routine has the side effect of re-initializing the
illumination angle utility package. Callers may
need to re-initialize the package after calling this routine.
MICE.REQ
GF.REQ
SPK.REQ
CK.REQ
TIME.REQ
WINDOWS.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Mice Version 1.1.0, 01-NOV-2021 (EDW) (JDR)
Changed the input argument name "illum" to "illmn" for
consistency with other routines.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections, and
edited -I/O section to comply with NAIF standard. Fixed minor typos in
header.
Updated header to describe use of expanded confinement window.
Edited the header to comply with NAIF standard.
Corrected error in header that listed 'SOLAR INCIDENCE' as an
allowed angle type rather than the correct value 'INCIDENCE'.
Eliminated use of "lasterror" in rethrow.
Removed reference to the function's corresponding CSPICE header from
-Required_Reading section.
-Mice Version 1.0.1, 11-NOV-2014 (EDW)
Edited -I/O section to conform to NAIF standard for Mice
documentation.
-Mice Version 1.0.0, 07-NOV-2013 (EDW)
solve for illumination_angle constraints
solve for phase_angle constraints
solve for solar_incidence_angle constraints
solve for incidence_angle constraints
solve for emission_angle constraints
search using illumination_angle constraints
search using lighting_angle constraints
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