Date: Jul 15, 2010 Author: Joan Zimmermann Source: MDA (
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by Joan Zimmermann/jzimmermann@nttc.edu
Fibertek, Inc. (Herndon, VA), has leveraged three Missile Defense Agency-funded SBIR awards to develop a suite of laser products, one of which now forms the basis for an important space weather platform.
The Fibertek products include a laser transmitter for space-based ladar platforms; single-photon-counting lidar receivers; and ultracompact, high-performance, 3-D lidar imaging systems. Of those three products, one, the company's laser transmitter, is now flying in space to aid weather observation, although the two other MDA-sponsored technologies also contributed to the transmitter's development.
Specifically, expertise developed under these MDA-funded projects has been parlayed into both the know-how and hardware underlying a laser transmitter now flying on NASA's CALIPSO satellite. The laser-based Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is the main instrument on CALIPSO, and its job is to collect lidar profiles of Earth's atmosphere. These lidar profiles provide information about particle backscatter, distribution and shape of clouds, and the composition of the atmosphere (such as smoke versus fog).
Fibertek acted as a subcontractor to Ball Aerospace in installing the CALIOP instrument, designing, building, and qualifying the laser transmitter for the CALIPSO satellite.
CALIPSO is one of NASA's "A Train (Afternoon Constellation) satellites," part of a series that provides complementary information to atmospheric scientists. CALIOP has the distinction of being the first polarization lidar instrument in space. Fibertek also provides continuing instrument support for on-board laser performance to help maximize the CALIPSO mission lifespan.
Launched in April 2006, CALIPSO and its sister spacecraft CloudSat are providing much needed information about Earth's atmosphere. In particular, CALIPSO's lidar instrument is helping to distinguish aerosol from cloud in Earth's atmosphere, while CloudSat uses a radar that is 1,000 times as sensitive as a typical weather radar system to examine how rain and snow form within clouds. The combined instrumentation, which provides valuable synchronous data points, will contribute to a better understanding of what drives our weather, helping scientists to construct more accurate predictive models.
To date, CALIOP has fired its lasers to acquire more than 2 billion lidar profiles. The spacecraft and its payload continue to function well, and may be extended beyond the original mission life by a number of years. CALIPSO has been credited with finding smoke at high altitudes over Australia during bushfire season, measuring the extent of sandstorms as they blow away from Tibet, providing a vertical profile of Hurricane Bill in 2009, and helping to demonstrate the warming effect of aerosols/particulates when trapped under cloud cover. NASA now provides some CALIPSO data via the Google Earth application.
The company also developed single-photon-counting lidar systems that provide precisely the type of functionality needed for the CALIOP instrument. Such a system can detect even a single quantum of reflected light (a weak return) and thereby improve the sensitivity of lidar where the object is very far away (hundreds of kilometers), helping to better sense the inherently weak return signal. And as for Fibertek's third product—the single-photon receiver developed under the original MDA SBIR—its size and weight have been estimated to be 10 percent of comparable systems, which offers cost savings tied to payload weight and volume reduction for spaceborne platforms.
More recently Fibertek built its laser expertise by developing small, lightweight lasers that featured rapid pulsing and high power output. Under one SBIR, Fibertek developed a high-repetition rate fiber laser transmitter to replace an existing low-repetition rate laser source. Laser transmitters help lidar and ladar devices bounce light off targets of interest, thereby revealing some of their physical properties. In previous work, Fibertek increased output power by a factor of twenty and increased the pulse frequency one hundred-fold. The new laser transmitter architecture also allowed for sub-nanosecond pulses, which had been previously difficult to achieve with older, longer pulse rate, solid-state lasers. The higher performance, lower cost, and higher reliability offered by the new transmitter made it ideal for space platforms, where long lifetimes and reliability are key.
As an outgrowth of this work, Fibertek recently won a five-year, $35 million contract to manage and develop laser instrumentation for NASA's IceSat II mission. This satellite will replace IceSat I, which began to suffer anomalies in October 2009. As its name implies, IceSat II will monitor the thickness of Earth's ice sheets and polar caps. Ice cover plays a role in reflecting solar radiation into space and is thought to be one of many factors influencing global temperatures. Fibertek offers many other laser-based products, including custom lasers, eye-safe rangefinders, and lidar systems for remote sensing and obstacle avoidance.
