The Manastash Ridge Radar Project

The Manastash Ridge Radar Interferometer is a bistatic passive radar system that uses commercial FM broadcasts as a signal source. The system is designed to operate between 88 and 108 MHz in frequency with data collection using multiple receivers synchronized using the Global Positioning System. The radar's function is the study of density irregularities in the ionosphere, primarily those associated with the auroral electrojet. The system may also be used to track aircraft, meteor trails, and other phenomenon.

Current Project Highlights

• Intial Bistatic Data Has Been Collected! Some bistatic data has been collected with one receiver deployed at the Manastash Ridge Site and the other at the UW. This first deployment has revealed a number of minor problems with the system that are now being collected. Signal processing software to analyze this data is rapidly being completed.
• Two Identical Receivers have now been completed. These receivers have been used in bistatic tests that have shown promising results. An upgrade to the receivers is underway to stabilize physical connectors and ready the system for permanent deployment. The system should be deployed by the end of October.
• Advanced PCI Digitizers were purchased from Datel corporation. These digitizers are capable of handling up to 4 receivers each using 2 data aquisition channels. Each channel is sampled simultaneously at 250KHz with continious data streaming into the host PC.

Other Project Highlights

• Manastash Ridge Observatory is now online! The Cylink radio modems are now fully operational connecting the observatory to the Internet. This is the first step in establishing a fully automated radar system. Thanks go to Jeff Morgan of the UW Astronomy Department as well as Mark Makela of Central Washington University for their help in getting this connection online.
• A GPS time-frequency receiver is now installed and online at the Manastash Ridge Observatory. This unit will permit time synchronization of remote radar receivers to less than 100ns and frequency synchronization to at least 1 Hz. Thanks go to the National Science Foundation for this first unit. A second unit has been aquired for use with the UW based receiver thus allowing us to synchronize operations across the ~100km seperating the two stations.
• Signal Processing Theory
• Mike Hansen's MS Thesis was about the fundamentals of the ambiguity function calculations needed to extract signal spectra from the complicated FM signal in the fourier domain.
• Paul Hall's MS Thesis investigated the ambiguity function in the autocorrelation domain using real data from a Hewlett Packard 89440 sampling an actual FM radio station.
• Deconvolution will probably be necessary to provide a better signal, somewhat free of nearby ground clutter.
• From Simple Experiments it appears that some airplanes have been detected. The most important result so far is that the FM signal has been experimentally proven to have excellent pulse compression --- 20 to 40 dB with 2 km range resolution is easy to get.