Re: [Orekit Users] CPython interface question

[Piyush Shanker Agram <piyush@gps.caltech.edu>]

I dont think the float statements are the problem. Python floats are 8 byte by default. Since orekit does not recognize numpy data types, I actually needed the explicit float conversions to make the transforms work.

The code crashes only on the final line. Intermediate results involving time and coordinate transforms seem to work fine. Here is the line where it crashes.

>	finState = orb_prop.propagate(startDate)

There are no problems reported when initializing the orbit or the propagator.

The message indicates something is wrong while parsing some arguments in JCC.CPP .

Thanks
Piyush


piyush@gps.caltech.edu wrote:

>Hi everyone,
>     I stumbled across orekit when looking for software for orbit propagation.
>I'm trying to propagate given state vectors (position + velocity) for SAR
>satellites in the forward and backward directions by a few minutes. I'm a heavy
>Python user and chose to try the CPython interface. The interface works pretty
>well and allows me to transform data easily between inertial and itrf frames.
>However, everytime I try to propagate the orbit (tried a couple of methods) -
>the program crashes with the following message. I'm not really familiar with
>JCC and have trouble interpreting this error.
>
># A fatal error has been detected by the Java Runtime Environment:
>#
>#  SIGSEGV (0xb) at pc=0x00007f44841f7c5a, pid=16722, tid=139932295845632
>#
># JRE version: 6.0_24-b24
># Java VM: OpenJDK 64-Bit Server VM (20.0-b12 mixed mode linux-amd64 compressed
>oops)
># Derivative: IcedTea6 1.11.5
># Distribution: Ubuntu 12.04 LTS, package 6b24-1.11.5-0ubuntu1~12.04.1
># Problematic frame:
># C  [_orekit.so+0x358c5a]  _parseArgs(_object**, unsigned int, char*,
>...)+0x218a
>#
>
>
>Here is my code segment. Any suggestions would be helpful.
>
>Thanks
>Piyush
>
>	setup_orekit_curdir()	   #Reads data and includes initVM
>
>	#####Setup the ECEF frame
>	ecefframe = orekit.FramesFactory.getITRF2005()
>	ae = orekit.Constants.WGS84_EARTH_EQUATORIAL_RADIUS
>	flt = orekit.Constants.WGS84_EARTH_FLATTENING
>	mu = orekit.Constants.WGS84_EARTH_MU
>	earth = orekit.OneAxisEllipsoid(ae, flt, ecefframe)
>
>	######Setup the ECI Frame
>	eciframe = orekit.FramesFactory.getEME2000()
>
>	######Setup time frame
>	utc = orekit.TimeScalesFactory.getUTC()
>
>	#####Read in data from ROI_PAC state vector file	
>	hdrdata = np.loadtxt('hdr_pts.rsc')
>
>	ihr, imin, isec = secs_2_hhmmss(hdrdata[0,0])
>	ipos = orekit.Vector3D(float(hdrdata[0,1]), float(hdrdata[0,2]),
>float(hdrdata[0,3]))
>	ivel = orekit.Vector3D(float(hdrdata[0,4]), float(hdrdata[0,5]),
>float(hdrdata[0,6]))
>	iVect = orekit.PVCoordinates(ipos, ivel)
>	itime = hdrdata[0,0]
>	iDate = orekit.AbsoluteDate(2012, 4, 30, ihr, imin, isec, utc)
>
>
>	#######Create transforms using this
>	eci2ecef = eciframe.getTransformTo(ecefframe, iDate)
>	ecef2eci = eci2ecef.getInverse()
>
>	eVect = ecef2eci.transformPVCoordinates(iVect)
>	initOrbit = orekit.KeplerianOrbit(eVect, eciframe,iDate, mu)
>	orb_prop = orekit.KeplerianPropagator(initOrbit)
>	orb_prop.setSlaveMode()
>	
>	startDate = orekit.AbsoluteDate(iDate,float(hdrdata[1,0]-hdrdata[0,0]),
>utc)
>	finState = orb_prop.propagate(startDate)