Orestis Ousoultzoglou

Hi @matbesancon! So, change each definition of `grad!` removing `storage` as an argument and return the value that would have been assigned to `storage`?

So, for example, instead of: ```julia function grad!(storage, x) @. storage = 2 * (x - xp) end ``` Something along the lines of: ```julia function grad_iip!(storage, x) @. storage...

I have a lot of questions. I've opened #373 to facilitate communication and will drop some comments there

### Consistency There are definitions like ```julia grad!(storage, p) = storage .= 2p ``` and ```julia function grad!(storage, p) @. storage = 2p return nothing end ``` or ```julia function...

Hey @OrbitalMechanic! > WARNING: AstropyDeprecationWarning: The private astropy._erfa module has been made into its own package, pyerfa, which is a dependency of astropy and can be imported directly using "import...

Also check https://github.com/poliastro/poliastro/issues/710 and https://github.com/poliastro/poliastro/issues/792, and consider dropping some feedback on the latter :)

Hey @superx458! Regarding RAAN being a weird string, does `orb_heli_test.raan.to(u.deg).value` cover you? Check [Astropy's documentation](https://docs.astropy.org/en/stable/coordinates/angles.html#id2) to understand what's going on under the hood 🚀

I am sorry, but I can't quite understand what you mean in point `2`. With that in mind: * Have you checked the [documentation on `Orbit.heliosynchronous`](https://docs.poliastro.space/en/latest/autoapi/poliastro/twobody/orbit/index.html#poliastro.twobody.orbit.Orbit.heliosynchronous)? * The equations here...

> but when I give it three variables semi_major, inclination, and eccentricity, it happily gives me a plot from the `Orbit.heliosynchronous()` code: ```python3 try: with np.errstate(invalid="raise"): if no parameter was...

It's great that the figure helped! It's also from Vallado, btw. Here's the caption, too:  I think a input validation could happen for this as well :) Also, I'd...