The Orekit library can be accessed from other languages, for integration into existing software or for quick prototyping in a scripting language such as Matlab, Python or Jython. This allows for direct interaction with the different objects, either from a script or directly at the command prompt, and quick access to plotting tools.
Matlab is a commercial tool for technical computation, with easy access to graphical plot routines. It can access Java libraries and convert the results to Matlab objects. It is important to get the orekit jar in the Matlab Java class path, which can be done by issuing the javaaddpath command or modifying the classpath.txt file in matlabroot/toolbox/local. Your current Java class path is displayed with the javaclasspath function. The example below uses javaaddpath to set the paths. Note that as of Matlab version 7.5.0 this needs to be copy-pasted from the script to the Matlab prompt.
%
% /* Copyright 2002-2021 CS GROUP
% * Licensed to CS GROUP (CS) under one or more
% * contributor license agreements. See the NOTICE file distributed with
% * this work for additional information regarding copyright ownership.
% * CS licenses this file to You under the Apache License, Version 2.0
% * (the "License"); you may not use this file except in compliance with
% * the License. You may obtain a copy of the License at
% *
% * http://www.apache.org/licenses/LICENSE-2.0
% *
% * Unless required by applicable law or agreed to in writing, software
% * distributed under the License is distributed on an "AS IS" BASIS,
% * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
% * See the License for the specific language governing permissions and
% * limitations under the License.
% */
%
% Translated from KeplerianPropagation.java to Matlab by Petrus Hyvönen 2011 as an
% example of how to access orekit from matlab
% the jars orekit-8.0.jar, hipparchus-core-1.0.jar, hipparchus-geometry-1.0.jar,
% hipparchus-ode-1.0.jar, hipparchus-fitting-1.0.jar, hipparchus-optim-1.0.jar
% and orekit-data.zip is in current matlab dir.
______
% These seems to work if pasted to prompt.
javaaddpath 'C:\ ... enter your path here ...\MATLAB'
javaaddpath 'C:\.. enter your path here ...\MATLAB\orekit-8.0.jar'
javaaddpath 'C:\.. enter your path here ...\\MATLAB\hipparchus-core-1.0.jar
javaaddpath 'C:\.. enter your path here ...\\MATLAB\hipparchus-geometry-1.0.jar
javaaddpath 'C:\.. enter your path here ...\\MATLAB\hipparchus-ode-1.0.jar
javaaddpath 'C:\.. enter your path here ...\\MATLAB\hipparchus-fitting-1.0.jar
javaaddpath 'C:\.. enter your path here ...\\MATLAB\hipparchus-optim-1.0.jar
%% do the imports
import org.orekit.errors.OrekitException
import org.orekit.frames.Frame
import org.orekit.frames.FramesFactory
import org.orekit.orbits.KeplerianOrbit
import org.orekit.orbits.Orbit
import org.orekit.orbits.PositionAngle
import org.orekit.propagation.SpacecraftState
import org.orekit.propagation.analytical.KeplerianPropagator
import org.orekit.data.DataProvidersManager
import org.orekit.data.ZipJarCrawler
import org.orekit.time.AbsoluteDate
import org.orekit.time.TimeScalesFactory
%% Configure Orekit. The file orekit-data.zip must be in current dir
DM=org.orekit.data.DataProvidersManager.getInstance()
crawler=org.orekit.data.ZipJarCrawler('orekit-data.zip')
DM.clearProviders()
DM.addProvider(crawler)
%% Initial orbit parameters
a = 24396159; % semi major axis in meters
e = 0.72831215; % eccentricity
i = (7.0)/180*pi; % inclination
omega = (180)/180*pi; % perigee argument
raan = (261)/180*pi; %right ascension of ascending node
lM = 0.0; % mean anomaly
%% Set inertial frame
inertialFrame = FramesFactory.getEME2000()
%% Initial date in UTC time scale
utc = TimeScalesFactory.getUTC();
initialDate = AbsoluteDate(2004, 01, 01, 23, 30, 00.000, utc)
%% Setup orbit propagator
%gravitation coefficient
mu = 3.986004415e+14
%Orbit construction as Keplerian
initialOrbit = KeplerianOrbit(a, e, i, omega, raan, lM, PositionAngle.MEAN, inertialFrame, initialDate, mu)
%Simple extrapolation with Keplerian motion
kepler = KeplerianPropagator(initialOrbit);
%% Setup propagation time
%Overall duration in seconds for extrapolation
duration = 180*60.0
%Stop date
finalDate = AbsoluteDate(initialDate, duration, utc)
%Step duration in seconds
stepT = 30.0
%% Perform propagation
%Extrapolation loop
cpt = 1;
extrapDate = initialDate
while extrapDate.compareTo(finalDate) <= 0
currentState = kepler.propagate(extrapDate);
fprintf('step %d: time %s %s\n', cpt, char(currentState.getDate()), char(currentState.getOrbit()))
coord=currentState.getPVCoordinates.getPosition;
P(:,cpt)=[coord.getX coord.getY coord.getZ]';
extrapDate = AbsoluteDate(extrapDate, stepT, utc);
cpt=cpt+1;
end
%%
figure;
plot3(P(1,:),P(2,:),P(3,:));
If you get errors from Matlab like this:
??? Error: File: orekit_test2.m Line: 12 Column: 8 Arguments to IMPORT must either end with ".*" or else specify a fully qualified class name: "org.orekit.frames.Frame" fails this test.
you can change the line:
import org.orekit.frames.Frame
to
import org.orekit.frames.*
Jython is a Java-based implementation of the Python language, and interfaces well to Java libraries. The number of Jython modules available for plotting is limited, but Java libraries can be used.
It is important that the orekit jar file and Hipparchus jars are in the Java CLASSPATH. This can be set manually at the command prompt, or by using an IDE such as Eclipse with PyDev. The file orekit-data.zip should be in the current directory, the same as your Jython files.
This example is a translation of the KeplerianPropagation.java example to Jython, showing a stepped Keplerian propagation.
/* Copyright 2002-2021 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
# orekit.jar,orekit-data.zip and Hipparchus jars in CLASSPATH through eclipse project
import java, os
from org.orekit.errors import OrekitException
from org.orekit.frames import Frame
from org.orekit.frames import FramesFactory
from org.orekit.orbits import KeplerianOrbit
from org.orekit.orbits import Orbit
from org.orekit.orbits import PositionAngle
from org.orekit.propagation import SpacecraftState
from org.orekit.propagation.analytical import KeplerianPropagator
from org.orekit.data import DataProvidersManager
from org.orekit.data import ZipJarCrawler
from org.orekit.time import AbsoluteDate
from org.orekit.time import TimeScalesFactory
from math import radians
# Configure Orekit. The file orekit-data.zip must be in current dir
DM = DataProvidersManager.getInstance()
crawler=ZipJarCrawler("orekit-data.zip")
DM.clearProviders()
DM.addProvider(crawler)
#Initial orbit parameters
a = 24396159 # semi major axis in meters
e = 0.72831215 # eccentricity
i = radians(7.0)# inclination
omega = radians(180) # perigee argument
raan = radians(261) #right ascension of ascending node
lM = 0.0 # mean anomaly
#Inertial frame
inertialFrame = FramesFactory.getEME2000()
#Initial date in UTC time scale
utc = TimeScalesFactory.getUTC();
initialDate = AbsoluteDate(2004, 01, 01, 23, 30, 00.000, utc)
#gravitation coefficient
mu = 3.986004415e+14
#Orbit construction as Keplerian
initialOrbit = KeplerianOrbit(a, e, i, omega, raan, lM,
PositionAngle.MEAN,
inertialFrame, initialDate, mu)
#Simple extrapolation with Keplerian motion
kepler = KeplerianPropagator(initialOrbit)
#Overall duration in seconds for extrapolation
duration = 90*60.0
#Stop date
finalDate = AbsoluteDate(initialDate, duration, utc)
#Step duration in seconds
stepT = 30.0
#Extrapolation loop
cpt = 1
extrapDate = initialDate
while extrapDate.compareTo(finalDate) <= 0:
currentState = kepler.propagate(extrapDate)
print "step %d: time %s %s" % (cpt, currentState.getDate(), currentState.getOrbit())
extrapDate = AbsoluteDate(extrapDate, stepT, utc)
cpt=cpt+1
This example is based on the VisiblityCheck.java, translated into Jython. It includes an example of subclassing of a Java object into a jython object.
/* Copyright 2002-2021 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
# Orekit and Hipparchus in CLASSPATH through eclipse project
import java, os
from org.orekit.data import DataProvidersManager
from org.orekit.data import ZipJarCrawler
from org.hipparchus.geometry import Vector3D
from org.orekit.bodies import BodyShape
from org.orekit.bodies import GeodeticPoint
from org.orekit.bodies import OneAxisEllipsoid
from org.orekit.errors import OrekitException;
from org.orekit.frames import Frame
from org.orekit.frames import FramesFactory
from org.orekit.frames import TopocentricFrame
from org.orekit.orbits import KeplerianOrbit
from org.orekit.orbits import Orbit
from org.orekit.propagation import Propagator
from org.orekit.propagation import SpacecraftState
from org.orekit.propagation.analytical import KeplerianPropagator
from org.orekit.propagation.events import ElevationDetector
from org.orekit.propagation.events import EventDetector
from org.orekit.time import AbsoluteDate
from org.orekit.time import TimeScalesFactory
from org.orekit.utils import PVCoordinates
from org.orekit.utils import IERSConventions
from math import degrees, radians, pi
# Configure Orekit
DM = DataProvidersManager.getInstance()
crawler=ZipJarCrawler("orekit-data.zip")
DM.clearProviders()
DM.addProvider(crawler)
# Initial state definition: date, orbit
initialDate = AbsoluteDate(2004, 01, 01, 23, 30, 00.000, TimeScalesFactory.getUTC())
mu = 3.986004415e+14
inertialFrame = FramesFactory.getEME2000() # inertial frame for orbit definition
position = Vector3D(-6142438.668, 3492467.560, -25767.25680)
velocity = Vector3D(505.8479685, 942.7809215, 7435.922231)
pvCoordinates = PVCoordinates(position, velocity)
initialOrbit = KeplerianOrbit(pvCoordinates, inertialFrame, initialDate, mu)
# Propagator : consider a simple Keplerian motion (could be more elaborate)
kepler = KeplerianPropagator(initialOrbit)
#Earth and frame
ae = 6378137.0 # // equatorial radius in meter
f = 1.0 / 298.257223563 #; // flattening
itrf = FramesFactory.getITRF(IERSConventions.IERS_2010, True) #; // terrestrial frame at an arbitrary date
earth = OneAxisEllipsoid(ae, f, itrf)
# Station
longitude = radians(45.0)
latitude = radians(25.0)
altitude = 0.0
station1 = GeodeticPoint(latitude, longitude, altitude)
sta1Frame = TopocentricFrame(earth, station1, "station1")
# Event definition
maxcheck = 1.0
elevation = radians(5.0)
class VisibilityDetector(ElevationDetector):
# Class for handling the eventOccured java. Example of subclassing
# a java class in jython
def __init__(self, maxCheck, elevation, topo):
ElevationDetector.__init__(self,maxCheck, elevation, topo)
def eventOccurred(self, s, increasing):
if (increasing):
print "Visibility on", self.topocentricFrame.getName(), "begins at" , s.getDate()
else:
print "Visibility on", self.topocentricFrame.getName(), "ends at" , s.getDate()
return self.CONTINUE
sta1Visi = VisibilityDetector(maxcheck, elevation, sta1Frame)
#Add event to be detected
kepler.addEventDetector(sta1Visi)
#Propagate from the initial date to the first raising or for the fixed duration
finalState = kepler.propagate(initialDate.shiftedBy(1500.0))
print "Final state : " , finalState.getDate().durationFrom(initialDate)