image – Use ffmpeg to convert .exr to .hdr environment map

There are several .exr environment maps at svs.gsfc.nasa.gov/4851/

I want to convert one of these .exr files into an .hdr environment map (RGBE / Radiance HDR).

The command:

ffmpeg -i starmap_2020_4k.exr starmap_2020_4k.hdr

Gives the following error:

Unable to find a suitable output format for ‘starmap_2020_4k.hdr’

starmap_2020_4k.hdr: Invalid argument

Most search results are concerned with using .exr to create HDR videos.

Does ffmpeg support such a conversion? What other parameters are needed?