ENH: Support for loading .STS files (and .XML associated meta files)

[t-esman]

Description

A method for loading .STS (standard time series) and .XML files into pysat.

Potential impact

This will allow for the addition of magnetometer data directly from PDS to be loaded into pysat. For example (https://pds-ppi.igpp.ucla.edu/item/urn:nasa:pds:maven.mag.calibrated:data.ss:mvn_mag_l2_2014284ss1s_20141011::1.1) magnetometer data from MAVEN and MGS are separated into .STS and .XML files. Other magnetometer data is likely similarly stored.

Potential solution(s)

An .sts loader already exists that is potentially compatible for pysat (written by tesman and j. gruesbeck (GSFC code 695)). However, it is limited to a resulting xarray dataset (Cannot yet produce pandas). Additionally, it does not load any meta and likely needs edits. Additional code is necessary.

Alternatives

The only alternative used so far has been to load the .STS file into IDL, save the file as a .sav and then open that with pysat. (MGS dataset)

Additional context

Noting that MGS files are stored with doy and a lack of an appropriate epoch/time. So these potentially have to be accounted for.

[jklenzing]

Thanks @t-esman! If the data series is 1D, you can post-process using dataset.to_pandas() to convert.