Aerospace Laser Beacons Light Up U.S. Satellites Around the World
Aerospace scientist Steven Beck earlier this year found himself aboard a Royal Australian Air Force (RAAF) C-17 headed for a remote region on the Indian Ocean coast of Australia. Seated behind two Australian pilots and next to his Aerospace colleague Michael Williams, Beck felt as though he was traveling to the farthest reaches of the Earth — and in many respects, he was.
As a leading researcher and developer of laser beacon technology, such excursions have grown more and more commonplace for Beck as the demand for on-orbit sensor calibration has increased. His initial trip involved the transportation of two of Aerospace’s mobile beacons— via the RAAF C-17— from Sydney to the coastal testing location. The Aerospace laser beacons were stationed for nearly three months of sensor testing in Western Australia.
Laser beacons are used to illuminate on-orbit infrared (IR) sensors such as those aboard Space Based Infrared System (SBIRS) satellites for calibration and testing purposes. Essentially, the beacon provides a static IR source on the ground at a precisely known location on the face of the Earth. As a result, when the beacon’s narrow laser beam reaches the overhead persistent infrared (OPIR) sensor, the sensor can detect that point source on the ground and be calibrated by using that specific, known location as reference.
The Aerospace laser beacon program has operated since 1971— when it was originally developed to support the first Defense Satellite Program (DSP) sensor. “Early on, we spent a long time using hydrogen fluoride lasers, which were enormous — they occupied whole rooms,” said Beck, who has worked at Aerospace for nearly 30 years. “Through the years, the need for mobile field-deployable beacon systems has driven technology developments … The current beacons are the most compact, rugged, and capable yet produced. They are housed in a mobile van and employ a diode-pumped solid-state laser designed in-house. The laser produces one watt of laser output power from a rugged package the size of a stick of butter.”
Since the OPIR sensors are in geosynchronous orbit — an orbit synchronized with the Earth’s rotational period— they are pinned to a specific location and only accessible in certain geographical locations. As a result, beacon mobility is essential to accessing the OPIR sensors regardless of their divergent, geosynchronous locations. The modern, transportable beacons allow for calibration trips to any number of locations around the globe. Western Australia was a recent beacon-related journey, but Aerospace has a number of new projects in the works, including the first remotely operated beacon, to be tested in the Mojave Desert at Edwards Air Force Base.
As cheaper and more efficient beacons are designed, the potential for new applications of the technology increases greatly. Beck is particularly enthusiastic about the role of laser beacons as potential quantifiers of carbon dioxide.
“Knowing how much carbon dioxide is in the atmosphere is important for measuring climate change and global warming,” said Beck. “You can take a laser beacon, on the ground, and shine it up to a satellite on the other side of the atmosphere. And then if you can tune the laser frequency to either on or off the carbon dioxide absorption you can measure how much carbon dioxide lies in the path of that laser beam.”
In a wider sense, Beck sees the carbon dioxide measuring application as a potential instrument for political enforcement. “If we can make these laser beacons very small and cheap, which we think we can do, they could be proliferated globally,” said Beck. “And they could serve as monitors and potentially as devices which could be used to verify treaties that, in principle, may happen in the future for carbon production. This is a method that isn’t easy to tamper with and is not expensive and not intrusive. We think that this is a possible concept for a global monitoring system for carbon dioxide in the atmosphere.”
In fact, Beck and colleague Pat Smith have recently submitted a patent that proposes using laser beacons and on-orbit sensors to measure a variety of greenhouse gases in the atmosphere.
The versatile nature of beacon technology lends itself to an ever-expanding amount of practical applications. Beck and his Aerospace team members seem determined to discover and push laser beacon technology to its next phase of widespread, technological relevance.