AEDC engineers test cutting-edge scene projection system in 7V space chamber

  • Published
  • By Philip Lorenz III
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  Engineers at AEDC are leading the way in evaluating and demonstrating leading-edge technology and facility upgrades that support space and air-borne defense systems testing for the Missile Defense Agency's (MDA) early detection and interception of missiles.

A new optical collimator that will enable the projection of space targets into a wider field-of-view has been installed in AEDC's 7V Space Chamber and is being tested to validate its ability to function effectively in the simulated cold of outer space.

"A collimator is a device that focuses parallel light to a point, and operating in reverse can make an object close at hand appear to be very far away, as if it were in space," said Dr. Heard Lowry, ATA Technical Fellow for Space Sensors.

"What's being tested in our 7V facility is called the Short Focal Length Collimator (SFLC), and will eventually be combined with a dynamic infrared scene projector, MDA's Optimized Array for Space-based Infrared Simulation (OASIS) resistive emitter array. A translator system will move the SFLC between the deployed and stowed positions inside the 7V Chamber so that the original collimator can still be utilized.

"In addition, a digital multi-mirror device (DMD), such as used in most visible projection systems, has been installed in the 7V Chamber and visible and near-infrared (NIR) projection of pertinent mission scenes will be demonstrated at cryogenic temperatures."

Dr. Lowry added, "The SFLC is a critical component of a new target simulation and background radiation projection system for our 7V Space Chamber."

This new capability is essential to evaluating all critical aspects of a sensor mission for both surveillance-type sensors and seekers, using high-fidelity static and dynamic target simulation with single or multiple targets.

Dr. Lowry said the goal of the test is to validate these systems that will add new capabilities in AEDC's 7V for the MDA and future customers.

Jim Burns, AEDC's space chambers lead and project manager for the test, said the validation of the collimator and DMD in 7V is the latest step in an ongoing effort undertaken since fiscal year 2009 to improve the chamber's capabilities.

"We had to design the overall system and the mounting structure, all of those things," he said. "We had to get that fabricated and installed into the chamber. A lot of it was fabricated by our Model Shop or by folks here on base. We have outsourced some of the optical components, but a lot of the fundamental structure was built in-house.

"Much of the design and integration can be attributed to the late Les Crosswy (former AEDC employee) and his meticulous engineering. This system is really a credit to his memory."

Burns also spoke about some of the challenges the project has presented.

"First of all you've got to make sure that installing this new system hasn't done anything to degrade our current system," he said. "Then we have to make sure that all the mechanisms function."

Burns compared the view projected through the facility's current collimator to what someone would see if they looked at the sky through a soda straw.

"You would see just a very tiny scene; your field of view would be very tight," he said. "By changing the focal length, the system will give us a wider field of view.

"The current field of view of our scene projector is around 0.1 degrees, which is very narrow. This new collimator will increase our view up to a full degree, which is a significant increase. A lot of our customers are looking for even wider fields of view," he said. "There are some missions now where they want to see, for example, the whole Earth."

Another important part of the test in 7V is a piggy-back effort that is a Small Business Innovation Research (SBIR) project for Orbital Sciences Corp., Huntsville, Ala.

Dr. Tommy Cantey, a research scientist for the company, is the lead for the SBIR portion of the test at AEDC's 7V.

Excited about the test, Cantey explained the test in layman's terms.

"Scenic projection is very much sort of analogous to, especially in our case, using the overhead projectors that people do PowerPoint presentations and give lectures with," he said. "We're taking that technology and instead of pointing it at a screen or someone's eye, we're actually pointing it at a sensor under test."

The sensors tested in facilities like 7V are electro-mechanical devices for detecting a missile by the electromagnetic signals emitted by the missile itself or its plume.

The system being tested in 7V projects such a realistic image onto a generic sensor that it is incapable of distinguishing between real and simulated sources.

"The test article [scene projection system] that we're testing is a large array of micro mirrors, about a quarter of the diameter of a human hair," he said. "There are about a million mirrors and all of these tip and tilt using the control electronics that we're able to modulate, or turn on and off.

"The light is projected onto something, [to] illuminate them with a flashlight or some sort of uniform light source - it could be an infrared source like a hot plate. What gets projected out is this nice, two-dimensional image. The sensor under test thinks that it is looking at the real world."

He added, "We've had great success with this and this is just another barrier that's getting removed to making this more suitable for other applications."

Cantey said his company has had a very solid and long-standing professional relationship with AEDC, and he has always enjoyed collaborating with people like Burns, Lowry and others in Arnold's Space and Missiles Ground Test Complex.

"I am very happy to work with AEDC," he said. "I can't say enough about working with those guys, they've been very nice and very supportive."