public void PassPrediction()
{
List <PassDetails> knownPasses = SetupKnownPasses();
CoordGeodetic geo = new CoordGeodetic(41.760612, -111.819384, 1.394);
Tle tle = new Tle("ISS (ZARYA)",
"1 25544U 98067A 15090.55997958 .00016867 00000-0 24909-3 0 9997",
"2 25544 51.6467 111.8303 0006284 156.4629 341.9393 15.55450652935952");
SGP4 sgp4 = new SGP4(tle);
/*
* generate 7 day schedule
*/
DateTime start_date = new DateTime(2015, 4, 13, 0, 0, 0); //DateTime.Now (true);
DateTime end_date = start_date.AddDays(7); //new DateTime (System.DateTime.Now.AddDays (7));
List <PassDetails> pass_list = new List <PassDetails>();
;
//Console.WriteLine("Start time: " + start_date.ToString());
//Console.WriteLine("End time : " + end_date.ToString());
/*
* generate passes
*/
pass_list = GeneratePassList(geo, sgp4, start_date, end_date, 180);
Assert.AreEqual(knownPasses.Count, pass_list.Count);
for (int i = 0; i < pass_list.Count; ++i)
{
Assert.AreEqual(knownPasses[i].ToString(), pass_list[i].ToString());
}
}
public double[][] getRV(double minutesAfterEpoch)
{
double [] r = new double[3];
double [] v = new double[3];
rec.error = 0;
SGP4.sgp4(rec, minutesAfterEpoch, r, v);
sgp4Error = rec.error;
double [][] outv = new double[2][];
outv[0] = r;
outv[1] = v;
return(outv);
}
/**
* Set the values to the ElsetRec object.
*/
protected void setValsToRec()
{
double deg2rad = Math.PI / 180.0; // 0.0174532925199433
double xpdotp = 1440.0 / (2.0 * Math.PI); // 229.1831180523293
rec.elnum = elnum;
rec.revnum = revnum;
rec.satid = objectID;
rec.bstar = bstar;
rec.inclo = incDeg * deg2rad;
rec.nodeo = raanDeg * deg2rad;
rec.argpo = argpDeg * deg2rad;
rec.mo = maDeg * deg2rad;
rec.ecco = ecc;
rec.no_kozai = n / xpdotp;
rec.ndot = ndot / (xpdotp * 1440.0d);
rec.nddot = nddot / (xpdotp * 1440.0d * 1440.0d);
SGP4.sgp4init('a', rec);
}
/**
* Parse the tle epoch format to a date.
*
* @param str
* @return
*/
protected DateTime parseEpoch(String str)
{
int year = (int)Double.Parse(str.Substring(0, 2).Trim());
rec.epochyr = year;
if (year > 56)
{
year += 1900;
}
else
{
year += 2000;
}
int doy = (int)Double.Parse(str.Substring(2, 5 - 2).Trim());
double dfrac = Double.Parse("0" + str.Substring(5).Trim(), CultureInfo.InvariantCulture);
rec.epochdays = doy;
rec.epochdays += dfrac;
dfrac *= 24.0d;
int hr = (int)dfrac;
dfrac = 60.0d * (dfrac - hr);
int mn = (int)dfrac;
dfrac = 60.0d * (dfrac - mn);
int sc = (int)dfrac;
dfrac = 1000.0d * (dfrac - sc);
int milli = (int)dfrac;
/*
* gc.set(Calendar.YEAR, year);
* gc.set(Calendar.DAY_OF_YEAR, doy);
* gc.set(Calendar.HOUR_OF_DAY, hr);
* gc.set(Calendar.MINUTE, mn);
* gc.set(Calendar.SECOND, sc);
* gc.set(Calendar.MILLISECOND, milli);
*/
DateTime mepoch = new DateTime(year, 1, 1);
mepoch = mepoch.AddDays(doy - 1);
mepoch = mepoch.AddHours(hr);
mepoch = mepoch.AddMinutes(mn);
mepoch = mepoch.AddSeconds(sc);
mepoch = mepoch.AddMilliseconds(dfrac);
// Specify that this is UTC
mepoch = DateTime.SpecifyKind(mepoch, DateTimeKind.Utc);
double sec = ((double)sc) + dfrac / 1000.0d;
int mon = mepoch.Month;
int day = mepoch.Day;
double [] jd = SGP4.jday(year, mon, day, hr, mn, sec);
rec.jdsatepoch = jd[0];
rec.jdsatepochF = jd[1];
return(mepoch);
}
public static DateTime FindCrossingPoint(CoordGeodetic user_geo, SGP4 sgp4, DateTime initial_time1, DateTime initial_time2, bool finding_aos)
{
Observer obs = new Observer(user_geo);
bool running;
int cnt;
DateTime time1 = new DateTime(initial_time1.Ticks());
DateTime time2 = new DateTime(initial_time2.Ticks());
DateTime middle_time = null;
running = true;
cnt = 0;
while (running && cnt++ < 16)
{
middle_time = time1.AddSeconds((time2 - time1).TotalSeconds() / 2.0);
/*
* calculate satellite position
*/
Eci eci = sgp4.FindPosition(middle_time);
CoordTopocentric topo = obs.GetLookAngle(eci);
if (topo.elevation > 0.0)
{
/*
* satellite above horizon
*/
if (finding_aos)
{
time2 = middle_time;
}
else
{
time1 = middle_time;
}
}
else
{
if (finding_aos)
{
time1 = middle_time;
}
else
{
time2 = middle_time;
}
}
if ((time2 - time1).TotalSeconds() < 1.0)
{
/*
* two times are within a second, stop
*/
running = false;
/*
* remove microseconds
*/
int us = middle_time.Microsecond();
middle_time = middle_time.AddMicroseconds(-us);
/*
* step back into the pass by 1 second
*/
middle_time = middle_time.AddSeconds(finding_aos ? 1 : -1);
}
}
/*
* go back/forward 1second until below the horizon
*/
running = true;
cnt = 0;
while (running && cnt++ < 6)
{
Eci eci = sgp4.FindPosition(middle_time);
CoordTopocentric topo = obs.GetLookAngle(eci);
if (topo.elevation > 0)
{
middle_time = middle_time.AddSeconds(finding_aos ? -1 : 1);
}
else
{
running = false;
}
}
return(middle_time);
}
public static double FindMaxElevation(CoordGeodetic user_geo, SGP4 sgp4, DateTime aos, DateTime los)
{
Observer obs = new Observer(user_geo);
bool running;
double time_step = (los - aos).TotalSeconds() / 9.0;
DateTime current_time = aos; //! current time
DateTime time1 = aos; //! start time of search period
DateTime time2 = los; //! end time of search period
double max_elevation; //! max elevation
running = true;
do
{
running = true;
max_elevation = -99999999999999.0;
while (running && current_time < time2)
{
/*
* find position
*/
Eci eci = sgp4.FindPosition(current_time);
CoordTopocentric topo = obs.GetLookAngle(eci);
if (topo.elevation > max_elevation)
{
/*
* still going up
*/
max_elevation = topo.elevation;
/*
* move time along
*/
current_time = current_time.AddSeconds(time_step);
if (current_time > time2)
{
/*
* dont go past end time
*/
current_time = time2;
}
}
else
{
/*
* stop
*/
running = false;
}
}
/*
* make start time to 2 time steps back
*/
time1 = current_time.AddSeconds(-2.0 * time_step);
/*
* make end time to current time
*/
time2 = current_time;
/*
* current time to start time
*/
current_time = time1;
/*
* recalculate time step
*/
time_step = (time2 - time1).TotalSeconds() / 9.0;
} while (time_step > 1.0);
return(max_elevation);
}
public static List <PassDetails> GeneratePassList(CoordGeodetic user_geo, SGP4 sgp4, DateTime start_time, DateTime end_time, int time_step)
{
List <PassDetails> pass_list = new List <PassDetails>();
Observer obs = new Observer(user_geo);
DateTime aos_time = null;
DateTime los_time = null;
bool found_aos = false;
DateTime previous_time = new DateTime(start_time.Ticks());
DateTime current_time = new DateTime(start_time.Ticks());
while (current_time < end_time)
{
bool end_of_pass = false;
/*
* calculate satellite position
*/
Eci eci = sgp4.FindPosition(current_time);
CoordTopocentric topo = obs.GetLookAngle(eci);
if (!found_aos && topo.elevation > 0.0)
{
/*
* aos hasnt occured yet, but the satellite is now above horizon
* this must have occured within the last time_step
*/
if (start_time == current_time)
{
/*
* satellite was already above the horizon at the start,
* so use the start time
*/
aos_time = start_time;
}
else
{
/*
* find the point at which the satellite crossed the horizon
*/
aos_time = FindCrossingPoint(
user_geo,
sgp4,
previous_time,
current_time,
true);
}
found_aos = true;
}
else if (found_aos && topo.elevation < 0.0)
{
found_aos = false;
/*
* end of pass, so move along more than time_step
*/
end_of_pass = true;
/*
* already have the aos, but now the satellite is below the horizon,
* so find the los
*/
los_time = FindCrossingPoint(user_geo, sgp4, previous_time, current_time, false);
PassDetails pd = new PassDetails();
pd.aos = aos_time;
pd.los = los_time;
pd.max_elevation = FindMaxElevation(user_geo, sgp4, aos_time, los_time);
pass_list.Add(pd);
}
/*
* save current time
*/
previous_time = current_time;
if (end_of_pass)
{
/*
* at the end of the pass move the time along by 30mins
*/
current_time = current_time.AddMinutes(30);
}
else
{
/*
* move the time along by the time step value
*/
current_time = current_time.AddSeconds(180);
}
if (current_time > end_time)
{
/*
* dont go past end time
*/
current_time = end_time;
}
}
;
if (found_aos)
{
/*
* satellite still above horizon at end of search period, so use end
* time as los
*/
PassDetails pd = new PassDetails();
pd.aos = aos_time;
pd.los = end_time;
pd.max_elevation = FindMaxElevation(user_geo, sgp4, aos_time, end_time);
pass_list.Add(pd);
}
return(pass_list);
}
