celestia-gnss/tle2ssc

#!/usr/bin/python3
# tle2ssc
# Convert a TLE into an .ssc file for Celestia
#
# Usage:
# tle2ssc [filename]
# Example:
# tle2ssc foo-tle.txt

import os
import math
from math import remainder
from datetime import datetime
from sgp4.api import Satrec, WGS72
from skyfield.api import EarthSatellite, load, wgs84

xpdotp = 1440.0 / (2.0 * math.pi)

# For now dev with just one Galileo satellite
satellite_name='GSAT0101'
satellite_number=37846

#satellites_url = 'http://celestrak.com/NORAD/elements/galileo.txt'
satellites_url = './extras/galileo-gnss/galileo.txt'
satellites = load.tle_file(satellites_url)

ts = load.timescale()
t = ts.now()
# 2022-05-20 02:17:30
#t = ts.utc(2022, 5, 20, 2, 17, 30)

by_number = {sat.model.satnum: sat for sat in satellites}
satellite = by_number[satellite_number]

satellite_radius=0.005
satellite_epoch=satellite.model.jdsatepoch
#    The unique satellite NORAD catalog number given in the TLE file.
# Use one defined above.
#satellite_number=satellite.model.satnum

#    Satellite classification, or else 'U' for “Unknown”
satellite_classification=satellite.model.classification

#    International designator
satellite_intldesg=satellite.model.intldesg

#    Full four-digit year of this element set’s epoch moment.
satellite_epochyr=satellite.model.epochyr

#    Fractional days into the year of the epoch moment.
satellite_epochdays=satellite.model.epochdays

#    Julian date of the epoch (computed from epochyr and epochdays).
satellite_jdsatepoch=satellite.model.jdsatepoch

#    First time derivative of the mean motion (ignored by SGP4).
satellite_ndot=satellite.model.ndot

#    Second time derivative of the mean motion (ignored by SGP4).
satellite_nddot=satellite.model.nddot

#    Ballistic drag coefficient B* in inverse earth radii.
satellite_bstar=satellite.model.bstar

#    Ephemeris type (ignored by SGP4 as determination now automatic)
satellite_ephtype=satellite.model.ephtype
#    Element number
satellite_elnum=satellite.model.elnum

#    Inclination in radians. Convert radians to degrees.
satellite_inclination=math.degrees(satellite.model.inclo)

# Satellite Inclination and Obliquity are the same
satellite_obliquity=math.degrees(satellite.model.inclo)

#    Right ascension of ascending node in radians. Convert to degrees.
satellite_ascending_node=math.degrees(satellite.model.nodeo)
satellite_equator_ascending_node=math.degrees(satellite.model.nodeo)

#    Eccentricity.
satellite_eccentricity=satellite.model.ecco

#    Argument of perigee in radians.
satellite_arg_of_pericenter=math.degrees(satellite.model.argpo)

#    Mean anomaly in radians.
satellite_mean_anomaly=math.degrees(satellite.model.mo)

#    Mean motion in radians per minute.
satellite_no_kozai=satellite.model.no_kozai
satellite_period=(1 / (satellite.model.no_kozai * xpdotp))

#    Revolution number at epoch [Revs]
satellite_revnum=satellite.model.revnum

# Semi-Major Axis
satellite_semimajor_axis=pow((pow(satellite_period,2) * 75371000000000),0.33333333)

# Rotation Offset
satellite_rotation_offset=((satellite_arg_of_pericenter)+(satellite_mean_anomaly)+360*
	((2451545-satellite_epochdays)/satellite_period-
	round((2451545-satellite_epochdays)/satellite_period)))

# Output for .ssc file
print('"', satellite_name, '-', satellite_number, '" ','"Sol/Earth" {',sep="")
print('    Class "spacecraft"')
print('    # Mesh "foo.3ds" XXX')
print('    radius', satellite_radius)
print()
print('  EllipticalOrbit {')
print('    Epoch', satellite_epoch)
print('    Period', satellite_period)
print('    SemiMajorAxis', satellite_semimajor_axis)
print('    Eccentricity', satellite_eccentricity)
print('    Inclination', satellite_inclination)
print('    AscendingNode', satellite_ascending_node)
print('    ArgOfPericenter', satellite_arg_of_pericenter)
print('    MeanAnomaly', satellite_mean_anomaly)
print('  }')
print('  Obliquity', satellite_obliquity)
print('  EquatorAscendingNode', satellite_equator_ascending_node)
print('  RotationOffset', satellite_rotation_offset)
print('  # Orientation  [  ]')
print('}')