The Long-term Evolution of Geosynchronous Transfer Orbits: atan3 (a, b) - File Exchange

Code covered by the BSD License

Highlights from
The Long-term Evolution of Geosynchronous Transfer Orbits

atan3 (a, b) four quadrant inverse tangent
ceqm1 (t, y) first order form of Cowell's equations of orbital motion
eci2orb1 (mu, r, v) convert eci state vector to six classical orbital
eci2orb2 (mu, gst0, omega, ut... convert eci state vector to complete set of classical orbital elements
gast1 (jdate) Greenwich apparent sidereal time
gdate (jdate) convert Julian date to Gregorian (calendar) date
geodet1 (rmag, dec) geodetic latitude and altitude
getdate interactive request and input of calendar date
getoe(ioev) interactive request of classical orbital elements
gettime interactive request and input of universal time
gravity (t, y) first order equations of orbital motion
jd2str(jdate) convert Julian date to string equivalent
julian (month, day, year) Julian date
moon (jdate) lunar ephemeris
oeprint1(mu, oev) print six classical orbital elements
om_constants astrodynamic and utility constants
orb2eci(mu, oev) convert classical orbital elements to eci state vector
r2r (x) revolutions to radians function
readgm(fname) read gravity model data file
readoe1(filename) read orbital elements data file
rkf78 (deq, neq, ti, tf, h, t... solve first order system of differential equations
sun1 (jdate) solar ephemeris
svprint(r, v) print position and velocity vectors and magnitudes
gto.m
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from The Long-term Evolution of Geosynchronous Transfer Orbits by David Eagle
Interactive MATLAB script that predicts the long-term evolution of geosynchronous transfer orbits.

atan3 (a, b)

function y = atan3 (a, b)

% four quadrant inverse tangent

% input

%  a = sine of angle
%  b = cosine of angle

% output

%  y = angle (radians; 0 =< c <= 2 * pi)

% Orbital Mechanics with MATLAB

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

epsilon = 0.0000000001;

pidiv2 = 0.5 * pi;

if (abs(a) < epsilon)
    y = (1 - sign(b)) * pidiv2;
    return;
else
    c = (2 - sign(a)) * pidiv2;
end

if (abs(b) < epsilon)
    y = c;
    return;
else
    y = c + sign(a) * sign(b) * (abs(atan(a / b)) - pidiv2);
end

Highlights from The Long-term Evolution of Geosynchronous Transfer Orbits

Highlights from
The Long-term Evolution of Geosynchronous Transfer Orbits