Cannot Generate Valid TLE from sgp4init
See original GitHub issueI was trying to use sgp4 to construct tles from orbital parameters using latest version (2.12)
I am getting invalid tles back, however. This seems to be because export_tle expects epochyr and epochdays to be set, but they don’t seem to be set by sgp4init.
Maybe this is user error, but I couldn’t quite figure it out.
Here’s the test I constructed (using the sgp4init example from the documentation):
from sgp4.api import WGS72, Satrec
from sgp4.exporter import export_tle
satrec = Satrec()
satrec.sgp4init(
WGS72, # gravity model
'i', # 'a' = old AFSPC mode, 'i' = improved mode
5, # satnum: Satellite number
18441.785, # epoch: days since 1949 December 31 00:00 UT
2.8098e-05, # bstar: drag coefficient (/earth radii)
6.969196665e-13, # ndot: ballistic coefficient (revs/day)
0.0, # nddot: second derivative of mean motion (revs/day^3)
0.1859667, # ecco: eccentricity
5.7904160274885, # argpo: argument of perigee (radians)
0.5980929187319, # inclo: inclination (radians)
0.3373093125574, # mo: mean anomaly (radians)
0.0472294454407, # no_kozai: mean motion (radians/minute)
6.0863854713832, # nodeo: right ascension of ascending node (radians)
)
tle = export_tle(satrec)
assert tle[0][18:32] != '00000.00000000'
Issue Analytics
- State:
- Created 3 years ago
- Comments:7 (3 by maintainers)
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I will attempt to validate correctness next. I have validated that there are realistic looking epoch dates present in the tle now.
I know it doesn’t make any sense, but for this application I don’t need precision.
I’ll comment today with a test for correctness.
I am now getting epochs in the tles.
I cannot believe how responsive you were on this, thank you!