1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
from collections import defaultdict
from skyfield.api import Topos, load
from .utils import chunks, deg_to_cardinal, seconds_to_minutes
ISS = "ISS (ZARYA)"
STATIONS_URL = "http://celestrak.com/NORAD/elements/stations.txt"
class Predictions(object):
def __init__(
self,
lat,
lng,
altitude=0,
tz="UTC",
satellite=ISS,
start=None,
days=10,
tle_file=None,
):
self.lat = lat
self.lng = lng
self.altitude = altitude
self.tz = tz
self.start = start
self.days = days
self.tle_file = tle_file.resolve().as_posix() if tle_file else STATIONS_URL
self.satellite = self.init_satellite(satellite)
self.location = self.init_location()
def init_stations(self):
return load.tle_file(self.tle_file)
def init_satellite(self, satellite):
satellites = self.init_stations()
by_name = {sat.name: sat for sat in satellites}
return by_name[satellite]
def init_location(self):
return Topos(latitude_degrees=self.lat, longitude_degrees=self.lng)
def get_next_days(self):
ts = load.timescale()
t0 = ts.now() if not self.start else ts.ut1_jd(self.start)
t1 = ts.ut1_jd(t0.ut1 + self.days)
return t0, t1
def get_position_details(self, t):
difference = self.satellite - self.location
topocentric = difference.at(t)
alt, az, distance = topocentric.altaz()
azimuth = int(az.degrees)
return {
"time": t.utc_iso(),
"degrees": int(alt.degrees),
"azimuth": azimuth,
"direction": deg_to_cardinal(azimuth),
"distance": int(distance.km),
}
def get_prediction_details(self, rise, culminate, zet):
length = int((zet - rise) * 86400)
return {
"length": length,
"length_mins": seconds_to_minutes(length),
"rise": self.get_position_details(rise),
"culminate": self.get_position_details(culminate),
"set": self.get_position_details(zet),
}
def get_prediction_events(self):
t0, t1 = self.get_next_days()
ts, _events = self.satellite.find_events(
self.location, t0, t1, altitude_degrees=self.altitude
)
# events are returned as 3-tuples of (rise, culminate, set)
# where rise/set are relative to given altitude
# docs mention the possibilibity of several culminations
# https://rhodesmill.org/skyfield/earth-satellites.html#finding-when-a-satellite-rises-and-sets
# but this doesn't seem to happen in our case
res = list(chunks(ts, 3))
if len(res[-1]) != 3:
# truncate the last event in case it's a partial one
res = res[:-1]
return res
def get_predictions(self):
preds = self.get_prediction_events()
return [self.get_prediction_details(*p) for p in preds]
def truncate_prediction_dates(self, pred):
for t in ["rise", "culminate", "set"]:
pred[t]["time"] = pred[t]["time"][11:][:-1]
return pred
def get_grouped_predictions(self):
preds = self.get_predictions()
res = defaultdict(list)
for pred in preds:
date = pred["rise"]["time"][:10]
res[date].append(self.truncate_prediction_dates(pred))
return res
|
