Strange Behavior of KeplerianOrbit

Orekit Python Wrapper usage
1

Hello everyone,

I may be overlooking something very trivial, but running the following code throws me a strange error:

p2 = Vector3D(float(pos_x_array[0])*1000, 
              float(pos_y_array[0])*1000, 
              float(pos_z_array[0])*1000)                  # in [m]

v2 = Vector3D(float(vel_x_array[0])*1000, 
              float(vel_y_array[0])*1000, 
              float(vel_z_array[0])*1000)                  # in [m/s]

PVcoord = PVCoordinates(p2, v2)

print(PVcoord)
print(type(PVcoord))

KeplerOrbit = KeplerianOrbit(PVcoord, ECI, initialDate, Mu_earth)

{P(882599.856801, 4329281.121656001, 5322653.8791438), V(-6626.5659551, 3337.3076321, -1611.2564281), A(0.0, 0.0, 0.0)}
<class 'org.orekit.utils.PVCoordinates'>
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [37], in <cell line: 14>()
     11 print(PVcoord)
     12 print(type(PVcoord))
---> 14 Keplerorbit = KeplerianOrbit(PVcoord, ECI, initialDate, Mu_earth)

TypeError: 'Orbit' object is not callable

KeplerianOrbit method is created as it should be but I have no idea why ‘Orbit’ object is not callable in my case. Any ideas on this issue?

Thank you for the discussion in advance,
Baris

2

Hey there,

Did you make sure that your Mu_earth is a Python float?
None of Orbit’s constructors are public so this could partially explain the error.

Best,
Romain.

3

Hi @Echulion,

Your code is not complete. It is really weird.
Here is mine,

mu = Constants.EIGEN5C_EARTH_MU
eme2000 = FramesFactory.getEME2000()
initialDate = AbsoluteDate('2022-08-08T03:53:06.891648', utc)
p2 = Vector3D(882599.856801, 4329281.121656001, 5322653.8791438)
v2 = Vector3D(-6626.5659551, 3337.3076321, -1611.2564281)

PVcoord = PVCoordinates(p2, v2)

print(PVcoord)
print(type(PVcoord))

KeplerOrbit = KeplerianOrbit(PVcoord, eme2000, initialDate, mu)
4

Hello @Serrof, yes I checked it again and it is a Python float.

Yes @lirw1984, I did not share the complete code since I thought that frame, absolute date and standart earth gravitational parameter are quite straight forward and obvious.

The code works well all by itself and I can get Kepler Elements with no problem, but when I want to check Kepler elements at each time step inside a propagation loop, it throws that error. Strange really.

5

Hi @Echulion,

OK. I’ve no idea what you are doing.

6

Hi @Echulion,

Your problem looks similar to the one in this post.
You may be missing an explicit cast to KeplerianOrbit here.

Quoting Petrus:

Does that solve your issue ?

7

Hello @MaximeJ, its good to see you :blush:

Yes, my problem is indeed the one you have shared in that post and @luc described it on the point. I’ve tried to explicitly cast my orbit but it still returns me “orbit” type as following:

p2 = Vector3D(float(pos_x_array[0])*1000, 
              float(pos_y_array[0])*1000, 
              float(pos_z_array[0])*1000)                  # in [m]

v2 = Vector3D(float(vel_x_array[0])*1000, 
              float(vel_y_array[0])*1000, 
              float(vel_z_array[0])*1000)                  # in [m/s]

PVcoord = PVCoordinates(p2, v2)

orbit = OrbitType.KEPLERIAN.convertType(CartesianOrbit(PVcoord, ECI, initialDate, Mu_earth))
print(type(orbit))
orbit = KeplerianOrbit.cast_(orbit)
print(type(orbit))

<class 'org.orekit.orbits.Orbit'>
<class 'org.orekit.orbits.Orbit'>

Considering the discussion made in the post you’ve shared, I would expect to get a KeplerianOrbit after casting. :man_shrugging:t3: