How CubeSats are Helping Address the Space Debris Problem: Results from the Polar Orbiting Passive Atmospheric Calibration Spheres

Satellite drag variability caused by the dynamics of the upper atmosphere is a major cause of orbit specification and prediction errors in Low Earth Orbit. The problem is particularly severe during geomagnetic storms. These storms can severely degrade the accuracy of conjunction analysis between debris and spacecraft with LEO perigees and all other resident space objects. The Polar Orbiting Passive Atmospheric Calibration Spheres (POPACS) were launched as secondary payloads on the September 29th, 2013 Falcon 9 launch. Their purpose is to provide stable and well defined atmospheric calibration objects leading to improved specification of atmospheric densities and satellite drag. POPACS consists of three spheres deployed successfully from a Planetary Systems Corporation CSD 3U CubeSat ejection system. Specially designed spacers separated the spheres during launch and deployment. After summarizing the POPACS mission parameters and design, we review early mission validation results including data comparisons with the Drag and Atmospheric Neutral Density Explorer as well as comparisons with various atmospheric models. We also look at the ability of the POPACS data to alert us to large changes in atmospheric densities and satellite drag during geomagnetic storms. Finally, we show that well-designed reference satellites, such as POPACS, can be used to calibrate the state of the atmosphere. This calibrated data can be used to improve global atmospheric modeling and orbital predictions for both space debris and active satellites