ORBITAL MOTION

                           Some Useful Constants
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General

The Universal Gravitational Constant (G) = 6.668 10-11 kg-1 m3 sec-2

The following values have been established by international agreement and
are exact as shown:
1 foot = 0.3048 m
1 (statue) mile = 1,609.344 m
1 nautical mile = 1852 m

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Time

1 mean solar second (smoothed) = 1 ephemeris second (to about 1 part in 108
length of a tropical year at 1900.0 = 31 336 925.975 ephemeris seconds
1 mean solar second = 1.002 737 909 3 mean sidereal seconds
1 mean sidereal second = 0.997 269 566 4 mean solar seconds
1 mean solar day = 24 h 03min 56s.555 4 of mean sidereal time
= 86,636.555 36 mean sidereal seconds
1 mean sidereal day = 23 h 56min 04s.090 54 of mean solar time
=86,164.090 54 mean solar seconds

Length of a Tropical Year (Vernal Equinox to Vernal Equinox) = 365.242 20
mean solar days
Length of a Julian Year = 365.25 mean solar days (by definition)

Greenwich Mean Sidereal Time (GMST) at 0h UT =
6h 38m 45s.836 + 86 401 84s.542 Tu + 0s.0929 Tu2 ,
where Tu is the number of Julian centuries of 36525 universal days,
elapsed since 12h UT on 1900 January 0.

G=6.67259E-11

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Earth

Equatorial Radius (a) = 6378 137.0 m (WGS 1984)
Polar Radius (b) = 6356 752.3 m (WGS 1984)
Flattening (f) = 1/298.257223563 (WGS 1984)
Mass (Me)= 5.98 10 ^ 24 kg
Semi-major axis (Epoch 1980.0) = 1.495 985 10^8 km (= 1 Astronomical Unit)
Eccentricity (Epoch 1980.0) = 0.016 718
Inclination of orbit (Epoch 1980.0) = 23.441 884o
Normal gravity g = 9.8064 - 0.0259 cos 2Phi ms-2, where Phi = geodesic
latitude
Geopotential coefficient J2 = 1082.7 10-6
Radius of the Geostationary Orbit = 42164.16 km = 6.6107 (Equatorial) Earth
Radii.

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Moon

Mass (Mmoon)= 7.380 1022 kg
Semi-major axis (Epoch 1980.0) = 384 401 km
Eccentricity (Epoch 1980.0) = 0.054 900
Inclination of Moon's orbit (Epoch 1980.0) = 5.145 396o

Surface gravity g = 1.62 ms-2

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Sun

Mass (Msun)= 1.991 10^30 kg
Solar Constant (intensity of solar radiation at mean earth distance):
I = 1.36 * 10^3 Joule/m2/sec
Surface gravity g = 274 m/s2

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 ASTRONOMICAL UNIT (AU) 
1 AU = 149,597,870.691 kilometers 

Definition: An Astronomical Unit is approximately the mean distance between
the Earth and the Sun. It is a derived constant and used to indicate distances
within the solar system. Its formal definition is the radius of an unperturbed
circular orbit a massless body would revolve about the sun in 2*(pi)/k days
(i.e., 365.2568983.... days), where k is defined as the Gaussian constant
exactly equal to 0.01720209895. Since an AU is based on radius of a circular
orbit, one AU is actually slightly less than the average distance between the
Earth and the Sun (approximately 150 million km or 93 million miles).