The proposed project entails the design and construction of an HF digital multichannel radar receiver system and associated HF receiving array for HAARP. With this addition, the HARRP HF facility will become a powerful diagnostic tool for probing the natural ionosphere and monitoring changes in the ionospheric plasma arising from HF wave-plasma interactions. In addition, the radar receiver paves the way for meteor orbit astronomy from high geographical latitudes. The new system is intended to be a permanent facility addition to HAARP. Data acquired with the HF radar system will be accessible over the internet with the aid of a Java-based user interface. File formats will conform to the NetCDF standard. The suggested system will provide new opportunities for observers to conduct experiments at HAARP. As part of the enhanced facility capability, it will be possible to perform experiments dealing with artificial periodic inhomogeneities, stimulated electromagnetic emissions, meteor-radar measurements of mesospheric neutral winds, meteor orbit studies of cometary debris, neutral wind observations via partial reflection techniques, natural D region electron density and electron-neutral collision profiles also obtained through partial reflections, observations of the HF-induced D region heating through cross modulation techniques, the use of the HAARP HF facility of an extremely high resolution ionosonde, the mapping of HF-induced filaments caused by thermal self-focusing in the F region, and finally the passive monitoring of HF background transmissions and beacons to assess the background state of the neutral ionosphere
