Poliastro: Error in natural and artificial perturbations

[ana-cp]

Hello, I am a aeropace engineering master student and I was trying to use the poliastro environment to perform a project for one of my classes.

I was trying to use the code to implement the J2 perturbation (the code I found here) when I encountered the following error:

TypeError                                 Traceback (most recent call last)
<ipython-input-3-5de11052fd1e> in <module>
     15 tofs = TimeDelta(np.linspace(0 * u.h, 100000 * u.s, num=2000))
     16 
---> 17 rr = propagate(
     18     orbit,
     19     tofs,

~\anaconda3\lib\site-packages\poliastro\twobody\propagation.py in propagate(orbit, time_of_flight, method, rtol, **kwargs)
    465         pass
    466 
--> 467     rr, vv = method(
    468         orbit.attractor.k,
    469         orbit.r,

TypeError: cowell() got an unexpected keyword argument 'ad'

This happened not only for the J2 perturbation but I also tried with the 3rd body code and got the same result. Maybe it is a problem with my poliastro version (I have the 0.15.dev0) because I checked with a friends computer and everything worked for him.

Thank you in advance and sorry for any incoveniences. :)

[DhruvSondhi]

Hello @ana-cp, Thank you for using Poliastro.
I would like to bring to your notice that the cowell() function defined here is undergoing some changes, in the development version, to incorporate a faster implementation. The current implementation doesn't take into account the argument ad.
I would suggest that you install, the 1.14.0 version of the library & please try to re-run the examples again. Kindly let us know for any further assistance 😄

[astrojuanlu]

Welcome @ana-cp , and thanks @DhruvSondhi for chiming in! The documentation you linked is the stable version, which works with poliastro 0.14.0:

https://docs.poliastro.space/en/stable/examples/Natural%20and%20artificial%20perturbations.html

But, if you want to use the development version (master branch on GitHub), you will need to check out this instead:

https://docs.poliastro.space/en/latest/examples/Natural%20and%20artificial%20perturbations.html

Notice that cowell doesn't receive ad anymore, but a function that describes the two-body motion:

def f(t0, state, k):
    du_kep = func_twobody(t0, state, k)
    ax, ay, az = atmospheric_drag_exponential(
        t0,
        state,
        k,
        R=R,
        C_D=C_D,
        A_over_m=A_over_m,
        H0=H0,
        rho0=rho0,
    )
    du_ad = np.array([0, 0, 0, ax, ay, az])

    return du_kep + du_ad


rr = propagate(
    orbit,
    tofs,
    method=cowell,
    f=f,
)

Let us know if this fixes the issue :)

[ana-cp]

Hello @astrojuanlu and @DhruvSondhi, thank you for your assistance and for your fast answer!

I tried using the development version for my problem but it did not work as I got a different error; so I downloaded the previous version of poliastro (0.14.0) as you suggested and then it worked. Thank you a lot and sorry for any inconvenience! :)