By flying at high altitudes, the device can map swaths of up to a few kilometers, making surveys of broad areas faster and more affordable. While the company has built a number of systems for Government clients, Sigma is now more interested in selling its data-gathering services, which is why the highly flexible HRQLS system was built.
With a grant through NASA’s Carbon Monitoring System, the University of Maryland recently worked with Sigma to map and quantify the forest cover, or biomass, of all of Garrett County, Maryland. The company was able to map the 1,700-square-kilometer area with a horizontal resolution of a few decimeters in about 12 hours, using half-overlapping flights.
“It’s cost-effective now to do an entire state or to do a whole country because of improvements in how much area we can cover,” Machan says, adding that this ability marks a paradigm shift for the lidar market, where current technology limits the size of such image collections due to high costs and low coverage ranges.
The company has been in talks with one agency that wishes to map an entire country in Africa. The work would monitor tree coverage, ensuring compliance with arboreal cap-and-trade agreements, and would also be useful to oil companies and others who need to know the topography beneath that canopy to plan pipelines, roads, and other infrastructure.
“Once you have a 3D map, you can use it for any and all of the above types of things,” Machan says.
Various states have talked with the company about having large portions or even the entirety of the state mapped, and one company approached Sigma with an interest in mapping the Chesapeake Bay. “We’re just at the point where a number of commercial customers are interested in having us start flying over really large areas,” Machan says.
The company still works closely with NASA. In 2010, Sigma provided components of Goddard’s airborne, photon-counting Multiple Altimeter Beam Experimental Lidar (MABEL), a test bed for the technology—again, much of it provided by Sigma—that will fly on the Agency’s Ice, Cloud, and Land Elevation Satellite 2 (ICESat-2).
“With photon counting, we’re able to get the same resolution with much less light than we would with other methods,” says Anthony Martino, instrument scientist for ICESat-2 at Goddard. The mission, scheduled to launch in 2017, will use multiple single-photon lidar beams to monitor changes in ice coverage at the poles, as well as watch tropical forest coverage. “The scientific goals of ICESat-2 are primarily to measure changes in the heights of polar ice sheets and thickness of ice in the polar oceans, and secondarily to measure the thickness of vegetation in lower latitudes,” Martino says.
The new satellite’s altimeter is known as the Advanced Topographic Laser Altimeter System (ATLAS).
This is a follow-on to the first ICESat mission, which flew between 2003 and 2010. The original ICESat altimeter had a single laser that used about 100 times the energy per pulse that ICESat-2’s six beams will use together, until the laser failed, with the result that the device had to conserve laser life by operating just a few months each year. “Instead of using a single, powerful pulse, now we’re using a lot of weaker pulses for the same resolution with less stress on the laser,” Martino explains.
From an altitude of about 500 kilometers, ATLAS will fire its six beams around 10,000 times per second—as opposed to the original ICESat’s 40 times per second—and 60 detector channels will register returning photons, creating an image by averaging the results of every 100 pulses or so. The price of a more reliable laser, Martino says, is the need for more complicated, difficult receiving and timing systems. Sigma was brought on board because, in addition to supplying the fundamental concept for the necessary photon-counting electronics, the company could demonstrate its ability to develop the intricate hardware and software to support the mission.
“It’s the most complex single thing I’ve seen at Goddard in the electronics domain,” says Greg Henegar, product design lead for ICESat-2’s main electronics box, adding that Sigma’s solutions were “extremely cleverly devised. It required a very efficient architecture of that electronics board just because of the sheer volume of data it’s receiving.”
“The Air Force paid for us to develop our own timer concept, and we were able to take that and give it back to NASA in the form of MABEL and ATLAS,” says Machan. “That kind of completes the circle, if you will.”
Not that the story ends there. While the company’s SPL technology begins its break into the commercial market, Sigma also worked on a study with NASA regarding the feasibility of using a similar system to orbit and completely map three of Jupiter’s moons, concluding that Callisto and Ganymede could be covered in two months each, while the smaller Europa would take just a month, all with better than 5-meter horizontal and 10-centimeter vertical resolution.
“John’s claim has always been that a single photon is the most efficient use of energy,” Machan says. “To have a tiny laser and a really sensitive detector is a nice solution for NASA instruments.”