Title of Presentation: Laser Communication, Clock Synchronization, and Ranging in Interferometric Space Missions

Primary (Corresponding) Author: Guido Mueller

Organization of Primary Author: University of Florida

Co-Authors: Rodrigo Delagillo, Ira Thorpe, Shawn Mitryk


Abstract:  Several NASA missions, like LISA, Lator, Maxim, any Grace follow-on mission, and others, utilize laser interferometer to measure changes in distances between the various spacecraft. These laser interferometers are usually interferometers with substantial arm length differences and require sophisticated phase measurement capabilities to reach their limit which is often set by shot noise or laser frequency noise. In many cases the measurement system is also required to synchronize and stabilize the clocks on each S/C and perform ranging measurements to retrieve the absolute distance between the S/C. In addition to this, the S/C also need to communicate directly with each other to exchange status information or exchange other data. Each of these tasks can usually be performed by customized individual systems, but it is much more desirable to combine all these tasks with the main interferometry to reduce mass and energy consumption. Such a multi-task system has to show that its various additional functions do not interfere with each other and especially not with the main interferometry. Our group has developed a scheme to exchange clock synchronization, clock stabilization, ranging, and data information using the main interferometer link and is currently in the process of studying implementation strategies to reduce the interference with the main interferometer signal.

This work is supported by NASA grant APRA04-0048-0006.