def load(fnames, tag=None, inst_id=None, tle1=None, tle2=None,
         alt_periapsis=None, alt_apoapsis=None,
         inclination=None, raan=0., arg_periapsis=0., mean_anomaly=0.,
         epoch=None, bstar=0., one_orbit=False, num_samples=None, cadence='1S'):