Then the detected pixels are clustered into blobs, and blob attributes are calculated. The history of each correspondence is summarized and recorded in a trackfile. Object attributes are used to eliminate the majority of trackfiles. The most restrictive attribute is the position of the blob in the image in relation to the spacecraft position and camera attitude. The intersections of lines are possible locations of true objects.
Attributes help bound the computational explosiveness of the process.
But with increasing observation time for each track, more confidence is gained in the results and more track files are kept in the memory. This calls for a parallel computer on board the spacecraft. If such a computer is present the tracks can be divided among different processors, significantly improving the execution time of the process and the reliability of the results. Such an improvement insures early detection of the object, providing enough time for the spacecraft to refocus and image the body of interest. The platform is considered stationary since it doesn't move much in the short period of time necessary to provide four required frames.