Session
Technical Session X: Advanced Technologies 1
Abstract
Future communications may use many small satellites flying as a cluster. Such a cluster helps to synthesize very large antennae in space, wherein each satellite becomes the node or element of the antenna structure. A key factor in such a cluster, is the positioning of satellites in absolute as well as relative terms and the time synchronization between them. Ultra Wide Band (UWB) techniques have promising applications for small satellites, because they require only a very small power and support both navigation and communication. In this paper a simple technique i.e ‘transmit and listen’ method is used to demonstrate the time synchronization between the members of the cluster. One member satellite, ‘mother’, is assumed to have the capability to retransmit or reflect back the signals from the ‘child’ satellites. To begin the process of synchronization, a child satellite transmits a pulse and starts a counter. The pulse reaches the mother and gets reflected back and received by the same child after a time equal to the round-trip delay. Using the time instants of the transmitted and received signals the clock offset is calculated. The offset is partially or fully corrected in the next transmission of the signals. By this process, the clock of child slowly gets synchronized with the mother. Matlab simulations show that synchronization is achieved within about 50 cycles. Once synchronized, subsequent pulses can be used to calculate the distance and thus maintain the formation using an appropriate relative navigation algorithm.
Presentation Slides
A Simple Time Synchronization Scheme for Satellite Clusters in Formation Flying
Future communications may use many small satellites flying as a cluster. Such a cluster helps to synthesize very large antennae in space, wherein each satellite becomes the node or element of the antenna structure. A key factor in such a cluster, is the positioning of satellites in absolute as well as relative terms and the time synchronization between them. Ultra Wide Band (UWB) techniques have promising applications for small satellites, because they require only a very small power and support both navigation and communication. In this paper a simple technique i.e ‘transmit and listen’ method is used to demonstrate the time synchronization between the members of the cluster. One member satellite, ‘mother’, is assumed to have the capability to retransmit or reflect back the signals from the ‘child’ satellites. To begin the process of synchronization, a child satellite transmits a pulse and starts a counter. The pulse reaches the mother and gets reflected back and received by the same child after a time equal to the round-trip delay. Using the time instants of the transmitted and received signals the clock offset is calculated. The offset is partially or fully corrected in the next transmission of the signals. By this process, the clock of child slowly gets synchronized with the mother. Matlab simulations show that synchronization is achieved within about 50 cycles. Once synchronized, subsequent pulses can be used to calculate the distance and thus maintain the formation using an appropriate relative navigation algorithm.
