Technical Notes for HPOP
HPOP uses the following values for various physical constants:
HPOP uses the following values for the differences among various astronomical time systems:
Time System | Difference | Unit |
---|---|---|
TAI-UTC | Tabulated based on leap seconds | seconds |
UTC-UT1 | Tabulated based on Earth Orientation Parameter file | seconds |
TAI-TDT | -32.184 | seconds |
The models for atmospheric drag and solar radiation pressure use the following default values:
Coefficient | Default Value |
---|---|
cD (coeff of drag) | 2.0 |
cR (coeff of solar radiation pressure) | 1.0 |
These coefficients are defined by the following expressions for the accelerations due to drag and solar radiation pressure.
Acceleration caused by drag is:
Acceleration caused by solar radiation is:
where:
CR = coefficient for solar radiation = 1 + , where is the surface reflectivity (approx. 0.95 for aluminum)
CD = coefficient for drag
AD = satellite cross-sectional area along velocity vector
AR = satellite cross-sectional area presented to the Sun
M = satellite mass
= atmosphere density
V = satellite speed relative to the atmosphere
K = fraction of the solar disk visible at satellite location
LS = luminosity of the Sun
c = speed of light
r = distance of satellite from Sun