search

skyfielders / python-skyfield

Elegant astronomy for Python
MIT License
1.41k stars 212 forks source link

How can you track the historical distance between two satellites with updating elsets? #947

Closed davidkurtenb closed 6 months ago

davidkurtenb commented 6 months ago

I am trying to capture the historical distance between two satellites but having trouble writing the logic to update the observed TLE when an updated TLE is made available. For example if have the 4 TLEs listed below but as the distance iterates through the differnt times how can I update to use the most recent TLE if the there is an new observation :

################# SAT 1 sat1_initial = EarthSatellite( '1 50322U 21129B 22225.62649072 -.00000331 +00000+0 +00000+0 0 9999', '2 50322 0.1164 164.1148 0002656 102.9776 51.8190 01.00428106002426' ) sat1_update=EarthSatellite( '1 50322U 21129B 22226.61217274 -.00000326 +00000+0 +00000+0 0 99990', '2 50322 0.1173 162.8746 0002740 104.0896 48.3189 01.00427772002433' )

################# SAT 2 sat2_initial = EarthSatellite( '1 52940U 22073A 24074.90684682 -.00000373 +00000+0 +00000+0 0 99995', '2 52940 1.5815 89.4725 0002301 223.4944 305.7281 01.00274601006105' ) sat2_update=EarthSatellite( '1 52940U 22073A 24075.04354795 -.00000372 +00000+0 +00000+0 0 99999', '2 52940 1.5818 89.4689 0002312 223.3247 355.2499 01.00274549006094' )

import numpy as np import matplotlib.pyplot as plt from skyfield.api import Topos, Loader, EarthSatellite

ts = load.timescale() de421 = load('de421.bsp') earth = de421['earth']

datetime_sample = sat1_initial.epoch.utc_datetime() year = datetime_sample.year month = datetime_sample.month day=datetime_sample.day hour=datetime_sample.hour

hours = np.linspace(hour,hour+24, 25) times = ts.utc(year, month, day, hours, 0) times_lst = sorted(times.utc_strftime()) print(times_lst)

separation_lst = []

sat1_pos = sat1_initial.at(times).position.km sat2_pos = sat2_initial.at(times).position.km separation = np.sqrt(((sat1_pos-sat2_pos)*2).sum(axis=0))# kilometers separation_lst.append(separation) change = separation[1:]-separation[:-1] # kilometers per minute range_rate = change 1E+06 / 60 # millilmeters per second

print(len(separation_lst))

brandon-rhodes commented 6 months ago

Since this doesn't involve a bug in Skyfield, I'm going to convert it into a Discussion, so that you can get help with your script in a Q&A format.