Best way to get the polar radius

I have a geos projection CRS object and I want to get the polar radius, but it seems like it is not computed.

Out[5]: 
<Projected CRS: +proj=geos +lon_0=-89.5 +a=6378137.0 +b=6356752.31 ...>
Name: unknown
Axis Info [cartesian]:
- E[east]: Easting (metre)
- N[north]: Northing (metre)
Area of Use:
- undefined
Coordinate Operation:
- name: unknown
- method: Geostationary Satellite (Sweep X)
Datum: unknown
- Ellipsoid: GRS 1980
- Prime Meridian: Greenwich

In [6]: crs = scn['C01'].attrs['area'].crs
In [9]: crs.ellipsoid.semi_major_metre
Out[9]: 6378137.0

In [10]: crs.ellipsoid.semi_minor_metre
Out[10]: nan

In [11]: crs.ellipsoid.is_semi_minor_computed
Out[11]: False

Does nan mean it wasn’t computed? How do I compute it? If this is a property can’t it be computed when I ask for it?

[djhoese]

I thought I had created an issue for this or brought it up on gitter but now I can’t find it. Let’s close this here and if it becomes something that is inconvenient enough I’ll make an issue with PROJ.

[djhoese]

Thanks! Now if only I could remember where I wanted to use this… 🤔