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FIGURE 1.6B ESA and JSpOC prediction comparison. This plot shows the difference between ESA and JSpOC orbits staying within 300 meters over a 7-day prediction period. ESA used onboard GPS data while JSpOC used SSN radar data to fit the orbit prior to the prediction. SOURCE: Denise Kaya, A9AC, Air Force Space Command, presentation to the Committee for the Assessment of the U.S. Air Force’s Astrodyamic Standards on October 11, 2011.

GPS-based tracking data. The two orbits were within about 50 meters of each other over the fit interval, and the 7-day predictions were within 300 meters (with the JSpOC prediction being more accurate, probably because of the more complex atmosphere density modeling in HASDM, although one test is not enough to assess overall performance differences). Figures 1.6A and 1.6B illustrate these results.

Commercial Users

The committee received presentations from the Iridium and Intelsat operators. The Iridium community seemed satisfied with the data they are receiving from JSpOC and looked forward to more detailed interaction. Since the collision of Iridium 33 with Cosmos 2251 in February 2009, the Iridium program has developed a more robust interface with the JSpOC. The Iridium representatives asserted that:

The Iridium Space Network Operations Center receives regular conjunction updates from the JSpOC and when necessary, we maneuver our satellites based on this information to avoid potential collisions. We believe this is a substantial first step in better information sharing between the government and industry and support even more robust interaction which can provide better and more efficient constellation operation. We continue to work with the government on an ongoing basis across a variety of fronts and forums, including ongoing efforts to exchange additional data that will help us to make even better-informed decisions in the future.6

The Intelsat representatives expressed some frustration with the lack of a close relationship with the JSpOC such as that of Iridium. They also cited some examples of interoperability problems involving differences with JSpOC on the computed position of an Intelsat object. Geostationary orbit communication satellites such as Intelsat

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6 Joe Pizzicaroli, Iridium Communications, Inc., “Panel Discussion,” presentation to the Committee for the Assessment of the U.S. Air Force’s Astrodynamic Standards on February 7, 2012.



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