The Elginfield Infrasound Array (ELFO)
The Elginfield infrasound array is located in the woodland region that surrounds the Elginfield Observatory (green areas in figure 1). The forest was originally planted more then 40 years ago to provide a means of blocking the light produced by the city of London , located to the south, and provide the telescope a darker observing site. Today the forest has matured and is now the home of the 4 elements that make up the Elginfield infrasound array (ELFO). Designed in a traditional triangular pattern, with an off-center central element, the array uses the differences in the arrival time of an infrasonic wave at each microbarometer to determine both which direction the wave originated (back azimuth) and its apparent velocity (trace velocity) across the array. Each element is connected to a centralized data system via a steel armoured TECK cable. This cable provides both power and data connections to each vault with built-in redundancy. More then 2000 metres of TECK cable were buried 18 inches (~46 cm) below ground at the site and wind their way across the property and through the trees to each vault. The furthest section (Southern Element) was more then a kilometre long alone!
Figure 1: Placement of Elements in the Elginfield Array
The Elginfield infrasound array went online on January 25th, 2006 with the purpose of working in tandem with observations at the IMS Infrasound array I10CA located in Lac du Bonnet, Manitoba. Locally the array will be used to monitor for regional meteor and global bolide infrasound as well as investigations into seismo-acoustic coupling with the collocated, 3-component, broadband POLARIS seismic station. Because of its location (The Elginfield array is the easternmost, publicly available, infrasound array in North America) and the suite of All-Sky cameras of the Southern Ontario Meteor Network, the Elginfield array is well suited as the basis for a meteor infrasound observatory. Details of early results from the meteor infrasound observatory can be found here. An example of the cables that the elements of ELFO use to dectect infrasound waves is shown in Figure 2.
Figure 2: 12 inch sample length of the TECK cable used at the Elginfield Infrasound Array.