GEO & MEO/LEO satellite alignment calculation

[philsellick]

Hi

I am trying to figure out if it is possible or of anyone has tried to derive the Time when a LEO/MEO satellite is directly in front of a GEO satellite from a specific lat/long position on earth (ie a Ground Station). We ar6e looking to predict when a ground station would need to stop transmission to a LEO/MEO satellite to avoid interference with the GEO one. I have the TLE's for both, but it would seem a very iterative process to derive the time when the LEO/MEO Azimuth/Elevation == GEO Azimuth/Elevation from a specific locaiton , wondering if there is quicker way than parsing through tons of data :-)

[brandon-rhodes]

Skyfield has a find_minima() routine that might help you. If you graph the .separation_from() angle between the two satellite positions, how often do minima occur? If they were, say, every 90 minutes, you could probably set find_minima() searching by providing it with data points maybe 30 minutes or 20 minutes apart—which would let you avoid, say, having to compute each satelllite's position for every second of the day to look for the moments when they're closest in the sky.

It would probably also save time to not bother to compute alt/az, but instead just watch for when the raw position vectors are closest.

[sellick-phil]

Brilliant thanks the below works, with some caveats, which we will work on, but will share here anyway should anyone want it. The below is a bit long winded but we are just experimenting for now . Using numba doesn't speed it up much as we use pandas not np for the dataframe analysis. We are really only interested if there is a potential conjunction, so we just check the angle of separation, for each min and then log the times, for analysis. I think however it is also showing angles through the earth as well (i.e. angle of separation but the opposite side) , as from London we see conjunctions from Geo Sats in Australia :-) . We will keep on it , but thanks very much again, very useful and I suspect and increasingly valuable thing that will be needed by operators, certainly regulators in the UK are asking for avoidance plans for TX now with GEO etc

for meo in meoSatTLE:
for geo in geoSatTLE:
meoSat = meoSatTLE[meo]
geoSat = geoSatTLE[geo]
for day in range (1,delta.days):
for hour in range(1,24):
for sat_min in range(1,60):
t = ts.utc(d1.year, d1.month, day, hour, sat_min)
usno = api.Topos(lat, long, elevation_m=elv)
pos1 = (meoSat - usno).at(t)
pos2 = (geoSat - usno).at(t)
AOS = pos1.separation_from(pos2)
if AOS.degrees <= conjunctionAngle:
timeStamp=d1+timedelta(days=day, hours=hour, minutes=sat_min)

[philsellick]

Ok thanks I will look at it . It is more to calculate the angle from the ground station so if the MEO satellite comes Infront of the GEO need to know specifically what times that happens. The beam angles are narrow so if the look angles are more than say 5' apart in both el & azm looking from the GS then thats fine Will dig some more, I think there will be an increasing need to do this and coordinate between LEO/MEO & GEO and to mute and unmute as per convention Phil Sellick. @psellick Phone : +44 7810 800 058

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On Mon, Nov 7, 2022, 3:11 PM Brandon Rhodes ***@***.***> wrote: Skyfield has a find_minima() <https://rhodesmill.org/skyfield/api.html#skyfield.searchlib.find_minima> routine that might help you. If you graph the .separation_from() angle between the two satellite positions, how often do minima occur? If they were, say, every 90 minutes, you could probably set find_minima() searching by providing it with data points maybe 30 minutes or 20 minutes apart—which would let you avoid, say, having to compute each satelllite's position for every second of the day to look for the moments when they're closest in the sky. It would probably also save time to not bother to compute alt/az, but instead just watch for when the raw position vectors are closest. — Reply to this email directly, view it on GitHub <#810 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABXTDZWEZA3KGUIZJHIQOVLWHEL27ANCNFSM6AAAAAARZGMW4A> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>