Northrop Grumman navigation products exceeded data collection and characterization test objectives and provided excellent robust performance during recent flight tests for the U.S. Air Force Research Laboratory's Automated Aerial Refueling (AAR) program in conjunction with the Air Force Flight Test Center's Test Operations Combined Test Force, the 190th Air Refueling Wing of the Kansas Air National Guard, and the Calspan Corporation.

The purpose of the AAR program is to develop the capability of refueling unmanned aircraft with the existing Air Force tanker fleet.

Employing a Learjet as a surrogate for an unmanned aircraft and a modified refueling tanker, Northrop Grumman's relative navigation software and LN-251 embedded global positioning system (GPS)/fiber-optic inertial navigation system (INS) provided the precise positioning information required in support of the simulated aerial refueling mission.

A series of 10 flight tests, which concluded on March 18, demonstrated that Northrop Grumman's relative navigation software could be successfully hosted in the LN-251. The test also exercised the LN-251's newly-added Ethernet interface as well as its embedded 24-channel GPS receiver with enhanced tracking capabilities.

"This flight test showed that our relative navigation solution can successfully support the AAR mission and can be utilized for future applications where moving vehicles must operate in close proximity to one another," said Dr. Charles Volk, vice president and chief technology officer for Northrop Grumman's Navigation Systems Division.

Northrop Grumman has been involved with the AAR program since its inception and has supplied hardware, program analyses and support for all flight tests. The recently tested improvements to the relative navigation system are designed to increase performance availability, continuity, integrity, and accuracy in all flight situations.

"The success of this flight test is especially notable because it demonstrates the ability of an embedded GPS/INS to host relative navigation processing," said Dr. Alex Fax, director of positioning, navigation and timing solutions at Northrop Grumman's Navigation Systems Division. "This redundant, INS-based architecture has been checked out in our Hardware-in-the-Loop facility and demonstrated in flight."

The LN-251 systems utilized for this demonstration are the smallest, lightest navigation-grade embedded GPS/INS units available. They contain a high-performance navigation-grade fiber-optic gyro-based inertial measurement unit, providing a compact and low noise precision navigation solution for the relative navigation applications.

The LN-251, with its digital interface, is easy to incorporate into new aircraft and avionics systems of existing aircraft. Its modular open architecture supports additional applications and evolving requirements.