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());
}
}
private bool IsEqual(CoordGeodetic geo)
{
bool equal = false;
if (latitude == geo.latitude &&
longitude == geo.longitude &&
altitude == geo.altitude)
{
equal = false;
}
return(equal);
}
private void ToEci(DateTime dt, CoordGeodetic geo)
{
/*
* set date
*/
m_dt = dt;
const double mfactor = Global.kTWOPI * (Global.kOMEGA_E / Global.kSECONDS_PER_DAY);
/*
* Calculate Local Mean Sidereal Time for observers longitude
*/
double theta = m_dt.ToLocalMeanSiderealTime(geo.longitude);
/*
* take into account earth flattening
*/
double c = 1.0
/ Math.Sqrt(1.0 + Global.kF * (Global.kF - 2.0) * Math.Pow(Math.Sin(geo.latitude), 2.0));
double s = Math.Pow(1.0 - Global.kF, 2.0) * c;
double achcp = (Global.kXKMPER * c + geo.altitude) * Math.Cos(geo.latitude);
/*
* X position in km
* Y position in km
* Z position in km
* W magnitude in km
*/
m_position.x = achcp * Math.Cos(theta);
m_position.y = achcp * Math.Sin(theta);
m_position.z = (Global.kXKMPER * s + geo.altitude) * Math.Sin(geo.latitude);
m_position.w = m_position.Magnitude();
/*
* X velocity in km/s
* Y velocity in km/s
* Z velocity in km/s
* W magnitude in km/s
*/
m_velocity.x = -mfactor * m_position.y;
m_velocity.y = mfactor * m_position.x;
m_velocity.z = 0.0;
m_velocity.w = m_velocity.Magnitude();
}
/**
* Update this object with a new date and geodetic position
* @param dt new date
* @param geo new geodetic position
*/
public void Update(DateTime dt, CoordGeodetic geo)
{
ToEci(dt, geo);
}
/**
* @param[in] dt the date to be used for this position
* @param[in] geo the position
*/
public Eci(DateTime dt, CoordGeodetic geo)
{
ToEci(dt, geo);
}
/**
* Set the observers location
* @param[in] geo the observers position
*/
public void SetLocation(CoordGeodetic geo)
{
m_geo = geo;
m_eci.Update(m_eci.GetDateTime(), m_geo);
}
/**
* Constructor
* @param[in] geo the observers position
*/
public Observer(CoordGeodetic geo)
{
m_geo = new CoordGeodetic(geo);
m_eci = new Eci(new DateTime(), geo);
}
/**
* ructor
* @param[in] latitude observers latitude in degrees
* @param[in] longitude observers longitude in degrees
* @param[in] altitude observers altitude in kilometers
*/
public Observer(double latitude, double longitude, double altitude)
{
m_geo = new CoordGeodetic(latitude, longitude, altitude);
m_eci = new Eci(new DateTime(), m_geo);
}
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);
}
/**
* Copy constructor
* @param[in] geo object to copy from
*/
public CoordGeodetic(CoordGeodetic geo)
{
latitude = geo.latitude;
longitude = geo.longitude;
altitude = geo.altitude;
}
