TIDDBIT Radar at Wallops Island
A TIDDBIT radar was deployed in the Chesapeake Bay area, near Wallops Island, Virginia to support a NASA rocket campaign to investigate the mechanisms by which mid-latitude Spread-F is generated. There is strong evidence that gravity waves propagating through the ionosphere are able to generate spread-F irregularities at mid-latitudes (Huang et al., 1994; Kelley et al., 1997; 2000; 2001). The radar measured TIDs at 200-350 km altitudes in the F-region before and during a rocket launch into the F-region during a spread-F event. The radar was deployed in April 2006 to support the rocket launch in the summer of 2006, and again in July of 2007 to support two launch windows in the Fall.
The Chesapeake radar was operated with a sampling interval of 30 seconds. This provides a 1-minute Nyquist period, which is well below the Brunt-Vaisala period (~5-10 minutes) for the F-region. The data was time-stamped with a GPS time-signal for accurate timing. A real-time display was developed to enable diagnosis and monitoring of the system as data was being logged.
Frequencies were selected to give maximum data coverage above the E-region critical frequency, but without penetrating the F-region at local times when spread-F is typically observed (post sunset). The dual-frequency operation provided vertical velocities in addition to horizontal velocities across the entire wave spectrum. A total of six frequency-options were selected based on ionospheric predictions for the launch period, to give maximum operational flexibility.