Example #1
0
        /// <summary>
        /// Gets rectangular heliocentric coordinates of minor body
        /// </summary>
        protected CrdsRectangular RectangularH(SkyContext c, T body)
        {
            // final difference to stop iteration process, 1 second of time
            double deltaTau = TimeSpan.FromSeconds(1).TotalDays;

            // time taken by the light to reach the Earth
            double tau = 0;

            // previous value of tau to calculate the difference
            double tau0 = 1;

            // Rectangular coordinates of minor body
            CrdsRectangular rect = null;

            // Rectangular coordinates of the Sun
            var sun = c.Get(SunRectangular);

            // Orbital elements
            var orbit = c.Get(OrbitalElements, body);

            double ksi = 0, eta = 0, zeta = 0, Delta = 0;

            int count = 0;

            // Iterative process to find rectangular coordinates of minor body
            while (Math.Abs(tau - tau0) > deltaTau && count++ < 100)
            {
                // Rectangular coordinates of minor body
                rect = MinorBodyPositions.GetRectangularCoordinates(orbit, c.JulianDay - tau, c.Epsilon);

                ksi  = sun.X + rect.X;
                eta  = sun.Y + rect.Y;
                zeta = sun.Z + rect.Z;

                // Distance to the Earth
                Delta = Math.Sqrt(ksi * ksi + eta * eta + zeta * zeta);

                tau0 = tau;
                tau  = PlanetPositions.LightTimeEffect(Delta);
            }

            return(rect);
        }
        private void DoTest(CrdsGeographical location, OrbitalElements oe, string testData, double errorR, double errorEq)
        {
            Regex regex = new Regex("^(\\S+)\\s+(\\S+)\\s+(\\S+)\\s+(\\S+)\\s+(\\S+ \\S+ \\S+) (\\S+ \\S+ \\S+)$");

            string[] lines = testData.Split('\n');
            foreach (string line in lines)
            {
                string dataLine = line.Trim();
                if (!string.IsNullOrEmpty(dataLine))
                {
                    var    match = regex.Match(dataLine);
                    double jd    = double.Parse(match.Groups[1].Value, CultureInfo.InvariantCulture);
                    double X     = double.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
                    double Y     = double.Parse(match.Groups[3].Value, CultureInfo.InvariantCulture);
                    double Z     = double.Parse(match.Groups[4].Value, CultureInfo.InvariantCulture);
                    string ra    = match.Groups[5].Value;
                    string dec   = match.Groups[6].Value;

                    var eqTest = new CrdsEquatorial(new HMS(ra), new DMS(dec));

                    var nutation = Nutation.NutationElements(jd);

                    var aberration = Aberration.AberrationElements(jd);

                    // True obliquity
                    double epsilon = Date.TrueObliquity(jd, nutation.deltaEpsilon);

                    // final difference to stop iteration process, 1 second of time
                    double deltaTau = TimeSpan.FromSeconds(1).TotalDays;

                    // time taken by the light to reach the Earth
                    double tau = 0;

                    // previous value of tau to calculate the difference
                    double tau0 = 1;

                    // Rectangular coordinates of minor body
                    CrdsRectangular r = null;

                    // Rectangular coordinates of the Sun
                    var sun = SunRectangular(jd, epsilon);

                    // Distance to the Earth
                    double Delta = 0;

                    // Iterative process to find rectangular coordinates of minor body
                    while (Math.Abs(tau - tau0) > deltaTau)
                    {
                        // Rectangular coordinates of minor body
                        r = MinorBodyPositions.GetRectangularCoordinates(oe, jd - tau, epsilon);

                        double ksi  = sun.X + r.X;
                        double eta  = sun.Y + r.Y;
                        double zeta = sun.Z + r.Z;

                        // Distance to the Earth
                        Delta = Math.Sqrt(ksi * ksi + eta * eta + zeta * zeta);

                        tau0 = tau;
                        tau  = PlanetPositions.LightTimeEffect(Delta);
                    }

                    // Test heliocentric rectangular coordinates
                    Assert.AreEqual(X, r.X, errorR);
                    Assert.AreEqual(Y, r.Y, errorR);
                    Assert.AreEqual(Z, r.Z, errorR);

                    double x = sun.X + r.X;
                    double y = sun.Y + r.Y;
                    double z = sun.Z + r.Z;

                    double alpha = Angle.ToDegrees(Math.Atan2(y, x));
                    double delta = Angle.ToDegrees(Math.Asin(z / Delta));

                    var eq0 = new CrdsEquatorial(alpha, delta);

                    var theta0 = Date.ApparentSiderealTime(jd, nutation.deltaPsi, epsilon);

                    var parallax = PlanetEphem.Parallax(Delta);

                    var eq = eq0.ToTopocentric(location, theta0, parallax);

                    // Test equatorial coordinates
                    Assert.AreEqual(eqTest.Alpha, eq.Alpha, errorEq / 3600.0);
                    Assert.AreEqual(eqTest.Delta, eq.Delta, errorEq / 3600.0);
                }
            }
        }