Battery Ventures of Wellesley, Mass., led the insider round, with contributions from Second Avenue Partners of Seattle and Pteranodon Ventures of Las Vegas.

All three of the current round's investors backed Insitu in May 2006 with a $23 million Series C, which followed a $4 million second round from Second Avenue Partners, as well as an unspecified amount of angel funding.

Steve Sliwa, president and CEO of Insitu, said the current financing came at an increase in valuation to the third round, although he declined to specify a value.

The Bingen, Wash., startup's small aircraft can fly unmanned for up to 20 hours on about 1.4 gallons of fuel while transmitting images and video, according to the company. Various branches of the U.S. military, including the Navy, Air Force and Marine Corps, deploy the aircraft for reconnaissance and surveillance purposes. Sliwa expects the bulk of the company's business to continue to come from the military for at least five years.

Although Insitu was founded in 1991, the company had fewer than five employees until it hatched a more ambitious growth plan in 2001. A partnership with Boeing Co. of Chicago the following year spurred rapid growth. The company now has about 250 employees and is adding more.

Insitu partnered with Boeing to develop its ScanEagle product line and Fugro Airborne Surveys to develop the GeoRanger product line.

Profitable since 2005, Insitu plans to use the new capital to develop and launch its small aircraft model. Called the Integrator, the 125-pound aircraft will have a payload bay able to carry 45 pounds of scientific or communications equipment.

"[Integrator] is about three times the size of [ScanEagle] and has some different types of missions in mind," Sliwa said. "One of its key features is its design to carry customer payloads."

The company will also fund growth with the capital.

"Over the last four years we've had 125% annual compound growth rate in revenues, and so that absorbs quite a bit of working capital," said Sliwa. "We're going to be a little bit above $75 million in sales, but we still have to scale up a little bit to be suitable for the public markets."

Sliwa said the company has looked at an initial public offering, noting that "an S-1 isn't imminent, but certainly we raised the money with the idea that we'd get a good return for our investors, and there's two ways to do that, through an IPO or a merger opportunity."

Indeed, Insitu's prospects for an IPO are looking quite good. A competing company AeroVironment Inc. went public at $17 in January and has seen its shares appreciate more than 40% from the offering price.

With revenues of $173.7 million for 2007, AeroVironment is estimating that its topline will increase 20% to 25% in fiscal 2008.