In conclusion, a debris avoidance system for ISS has been implemented which allows assessment of risk reduction, minimizes maneuvers, and is very cost effective. The method requires accurate estimates of the state vector and state vector covariance estimate for both the space vehicle and the conjuncting object. The covariance data from the orbit determination software matches observation statistics for low drag objects. The covariance from the orbit determination software is scaled for high drag objects. With the current debris avoidance system, there is a risk reduction of from 80 to 85 percent with about 2 maneuvers per year.
Improvements continue to be made to the system.
Primarily, this consists of a detailed analysis of the Shuttle sensitive surfaces with the Bumper code to determine the debris and meteoroid risk to the vehicle and mission. Each mission has a target risk level that can be altered by the flight geometry during the mission. This risk calculation is based on the standard debris and meteoroid models and does not take into account short time-scale variations in the collision risk. For this reason several analyses are performed to estimate any enhancement to the baseline risk for a particular mission. The first source of possible enhancement is that an annual meteoroid shower could peak during the mission that might temporarily increase the net meteoroid flux over the short two-week Shuttle mission.