global ephemeris data cache

[nicHoch]

add a internal ephemeris data cache. This allows to bypass hidden internal FIDO searches and downloads of the same data multiple times

All coordinate transform and imaging methods might internally search for correct ephemeris data for higher precession.
To get the ephemeris data a FIDO search (defaults to our stix data server) is uses and data gets downloaded.

The ephemeris data search utilises a global cache in order to avoid unnecessary network traffic or file loading. ANC ephemeris fits files are organised as daily files. The entire day is put to cache if touched once.

A user can prefetch or pinpoint specific ephemeris data files with the `load_ephemeris_fits_to_cache(filename)' method.

    from stixpy.coordinates.transforms import load_ephemeris_fits_to_cache

    start_time = Time("2023-01-01T12:00:00")
    end_time = Time("2023-01-01T12:30:00")
    query = Fido.search(
        a.Time(start_time, end_time),
        a.Instrument.stix,
        a.Level.anc,
        a.stix.DataType.asp,
        a.stix.DataProduct.asp_ephemeris,
    )

    aux_files = Fido.fetch(query["stix"])
    for file in aux_files:
        load_ephemeris_fits_to_cache(file)

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.89%. Comparing base (c46bfcd) to head (8d9287d).

Files with missing lines	Patch %	Lines
stixpy/utils/table_lru.py	91.93%	5 Missing ⚠️
stixpy/product/sources/anc.py	87.09%	4 Missing ⚠️
stixpy/coordinates/transforms.py	94.11%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #165      +/-   ##
==========================================
+ Coverage   81.54%   81.89%   +0.35%     
==========================================
  Files          35       37       +2     
  Lines        2439     2558     +119     
==========================================
+ Hits         1989     2095     +106     
- Misses        450      463      +13     

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[samaloney]

Yea this is very different from what I was thinking but that not a bad thing, any idea on performance? As the reason I added the cache in the first place was because this code is call a lot during plotting operations.

It would be nice to be disable the cache maybe add a module level variable. Needs some narrative documentation could be added to top of the rst file and also needs a corresponding change log.

In the future if we have different version of the anc-ephem files and I wanted to compare the results from V0X to V0Y is this in the table or does the user have to remember which one the loaded last so will be in the cache? It would probably be useful to know which file the data came from anyway for debugging purposes anyway

[samaloney]

@nicHoch I force pushed, sorry, so don't forget to pull the changes back down to your local branch.

[samaloney]

pre-commit.ci autofix