1 VERIFYING OBSERVATIONAL DATA FOR REAL-WORLD SPACE SITUATIONAL AWARENESS David A. Vallado * In practice, Space Situational Awareness (SSA) requires precise knowledge of all objects in orbit. A complete, robust and accurate SSA system is necessary for accurate conjunction analysis (CA) and Radio Frequency Interference (RFI) de- termination. The Space Data Association fuses data from multiple sources to support state-of-the-art CA and RFI operations. Implementation requires signifi- cant work including a detailed verification effort to monitor and ensure interop- erability and compatibility. This paper summarizes the various data assembly, conversion, and OD operations to support this effort. The attention to detail re- quired at each step is shown, including the effect that time and coordinate sys- tems have on a computed conjunction. INTRODUCTION Space Situational Awareness (SSA) requires precise knowledge of all objects in orbit. It is a basic re- quirement for conjunction analysis (CA), radio frequency interference (RFI) calculations, etc. I define SSA as the process by which an organization maintains a catalog of all objects in space, to some level of accu- racy at epoch and at future times, and in a timely fashion. Several relevant attributes are discussed in Val- lado (2007: 831-834): complete and robust, timely and efficient, standardized and maintainable, accurate, and importantly, trusted. We build on the basic SSA principles to establish the conjunction and RFI analysis operations required to support the Space Data Association (SDA). The fundamental data currency for these analyses is the pre- cise ephemerides and associated parameters and filters used for the operations. Because each owner opera- tor system is unique, relying on different data sources, orbit determination schemes, ground sensors, etc., periodic evaluations are performed with the raw observational data from each owner operator to ensure the data is being used in the most efficient and accurate manner. This includes close and private communica- tion with each owner operator should any anomalies be observed. The operation is a professional look at improving the overall system and further enhancing the safety of each owner operator’s satellites. This paper describes the processes for the routine OD evaluations including the activities required to as- semble and process the data. The paper also explores the degree to which small changes can affect the ov- erall results of the conjunction calculations. SDA OPERATIONS AND BACKGROUND Since May 2004, the Center for Space Standards and Innovation (CSSI) has been providing daily re- ports of likely conjunctions for the upcoming week for all objects in Earth orbit using the full catalog of * Senior Research Astrodynamicist, Analytical Graphics Inc., Center for Space Standards and Innovation, 7150 Campus Dr., Suite 260, Colorado Springs, Colorado, 80920-6522. Email, dvallado@agi.com . AAS 11-439