Characterization of Sun Synchronous Orbits

The node rate due to the J2 coefficient in Earth's gravitational field is given by

Wj2 = -3*(Req/p)^2*n*J2*cos(i)/2

where the perturbed mean motion is given by

n = sqrt (mu/a^3)*(1+3*J2*(Req/p)^2*(3*(cos(i))^2-1)/(4*sqrt(1-e^2)))

The period of the orbit is given by

T = 2*pi()/n

The angle, Dlong, between successive ascending nodes, measured in the equatorial plane, is given by

Dlong = (-We + Wj2)*T

and the distance along the equator between successive node crossing points is given by

Dist = Dlong*Req

a = r (for circular orbits only)

p = a * (1 - e^2)

r = Req + ALT (altitude at the ascending node point)

StInputNameOutputUnits Comments
6378.16ReqkmEquatorial radius of Earth
398598.15mukm^3/s^2Earth's gravitational parameter
7.2921E-5Werad/sEarth's rotation rate
J2Oblateness Coefficient
1.991E-7Wj2rad/sSunsynch Node Rotation due to J2
LALT kmAltitude
La6150.0235kmSemi-major Axis of Orbit
0eEccentricity of Orbit
L95idegInclination of Orbit
p6150.0235kmOrbit Parameter
Lr6150.0235kmRadius of Orbit
LT4803.9284secPeriod of Orbit
n.00130793sec^-1Mean Motion of Orbit
LDlong-20.01639degChange in Ascending Node per Rev
LDist-2228.222kmDistance between successive nodes


Last Modified: Thurs June 26 1997