Filename convention for unnumbered bodies

[jessie-dotson]

Following up on a comment in the EDR1 readme... All moving bodies will have a preliminary designation. Other than some moving bodies discovered early (which now have numbers), they have the format YYYY ll## - for example 1999 KW4. Horizons has a convention for their "primary designation field" (aka pde). If an object has a number, the PDE will be the number, otherwise it'll be the preliminary designation.

One proposal for filename convention for all moving bodies would be to use the Horizons pde in the filename. (Perhaps, dropping the spaces?) I think that would work for all asteroids and comets... (Which either have "numbers" like 6P or preliminary designations like 2021 G1. (Using the comet names could get dicey because they have backslashes in them...)

[barentsen]

I like it. Using the Horizons PDE seems like a good convention to use. I will implement this! Thank you!