BACKGROUND AND SCIENCE

            By placing a satellite in low-Earth orbit, we can measure atmospheric density by observing the satellite’s position, velocity, and acceleration over time.  Through the use of the drag equation,

where D is the force due to drag, C_d is the coefficient of drag, V_∞ is the free-stream velocity 

of the satellite, and A is the cross sectional area of the satellite in the RAM direction, we can 

take simple knowledge of a satellite, known either before launch or determined while in 

orbit, and determine the local density of the atmosphere.

            While this is a very simple concept and this experiment has been done in the past with other satellites already in orbit, the cross sectional area of the satellite was not an exact determination in other calculations.  Instead, other agencies, to include the Defense Meteorological Satellite Program (DMSP), used an approximated cross sectional area based on the view of the satellite in the RAM direction.