Flir Systems ( FLIR) is a $4 billion market cap homeland security company that is focused on thermal imaging systems that enable the watchers to see at night. In addition, the company's detection division helps design instruments to detect biological, chemical, nuclear and radiological threats to homeland security. It is relatively safe to assume that government contracts to this mission-critical company are protected. Shares of Flir are down more than 30% since budgetary concerns began to dominate headlines early this summer. Investors should use the discount to as an opportunity to buy shares. Although the company has missed estimates slightly in each of the last three quarters, its prospects for growth remain impressive. The average Wall Street estimate is for the company to make $1.40 per share in the current year, with that number growing 25% to $1.75 per share in 2012. Investors can buy that growth for just 18 times current-year estimated earnings. That is a bargain in my book for a company that plays an important role in national security. Flir, one of the top-yielding aerospace and defense stocks, shows up on a recent list of 10 Stocks That Avoid the September Slump.