LAS CRUCES >> A small group of researchers and technicians recently gathered on a dirt airstrip at the U.S. Department of Agriculture Jornada Experimental Range to launch a Bat 4 unmanned aircraft on a mission, flying through both military restricted airspace and the National Airspace System.
“We do rangeland monitoring, and it’s a way to gauge rangeland health to see how the plants are doing over the course of the year,” said Connie Maxwell, USDA biological science technician and New Mexico State University affiliated faculty member.
This specific flight is one of a series that will monitor plant growth cycles for a USDA scientist studying vegetation response to climate. The scientist selects the flight dates in conjunction with satellite over-flights to compare the images.
“We were doing an imagery flight,” Maxwell said. “We have several sites out on the Jornada that we do repeat imagery on. This was a baseline flight for the year, before things start growing. In a couple of months, we’ll go back and do the same flights we did that day and see the green of the vegetation out there, and then later on in the year, we’ll see peak times, we’ll catch peak biomass, then at the end of the year when the plants start dying.”
The vegetation study is one of many that Maxwell and her colleague Amy Slaughter, USDA biological science technician and NMSU affiliated coordinator and graduate student, support with imagery from unmanned aircraft flights each year.
Each flight is the culmination of several weeks of work, determining the logistics of what the crew will do on flight day.
“As many times as we’ve done these flights, they’re never the same,” Maxwell said. “There’s always some kind of a change, so you basically have to start from scratch. We got a new airplane that we just started using last year, so basically we have to redo everything because it’s a totally different system.”
The use of unmanned aircraft at the Jornada Range dates back to 2006.
The Bat 4, manufactured by the MLB Company, has a 13-foot wingspan.
The smaller Bat 3 that Maxwell and Slaughter still occasionally use has a six-foot wingspan, but carries a much smaller payload.
A payload is the total complement of equipment carried by the aircraft, in this case, cameras.
The Bat 4 can carry a 20-pound payload of two cameras: a Canon SLR 21-megapixel camera and a Tetracam mini multi-camera array.
With each Tetracam exposure, six camera lenses capture separate bands of visible or near-infrared radiation to form a separate, monochromatic image on each camera sensor. The images allow researchers to make several determinations about the depicted vegetation.
Many processes must be completed before each flight, so flight days are an intense flurry of activity, from setting up computers and monitors in the ground control station, to mounting antennas used for communicating with the aircraft and other ground crews, to taking it all down at the end of the mission.
“We try to get there at least an hour and a half before our estimated launch time because it takes awhile to get everything set up,” Maxwell said. “We have checklists we have to go through to make sure we verify everything with the aircraft and the ground station before each flight.”
On this specific flight day, the crew flew the Bat 4 in both the National Airspace System and military restricted airspace controlled by White Sands Missile Range.
The USDA conducts flights under the NMSU Physical Science Laboratory’s Unmanned Aircraft Systems Flight Test Center Federal Aviation Administration Certificate of Authorization, which permits flights in more than 15,000 square miles of coordinated airspace in southwestern New Mexico.
The PSL UAS Flight Test Center staff handles the FAA notifications, while the USDA crew coordinates with White Sands.
Maxwell and Slaughter take turns serving as the internal pilot and payload specialist on flight days.
“When working as internal pilot, we’re monitoring the ground station computer when the flight is taking place,” Slaughter said. “My other role is to be the payload specialist — that is the person who is reading off the checklists, performing the 15-minute checks that we do as the aircraft is flying, recording the data we can see on the screen for all of the plane’s systems: fuel, batteries, link, etc.”
“We have a computer and an external monitor because we have so many things that we have to watch during the flight,” Maxwell said. “We have the main display showing the map of where we are and where we’re going. That’s where we load the flight plans and send them to the airplane. We are watching the primary flight display to make sure the airplane is behaving correctly, so it’s just like being in a regular airplane – you have to keep tabs on what’s going on.”
In addition to Slaughter’s and Maxwell’s roles on a flight day, there are several other people on the ground to make each flight a success. The PSL FTC supplies a mission commander, spectrum analyst and visual observers, while USDA personnel act as external pilot, external pilot communicator and visual observers.
Following FAA requirements, the external pilot stays within 0.6 miles of the airplane, maintaining a line of sight. Observers monitor the airspace in search of any aircraft that might enter the Bat 4’s flight plan.
The external pilot uses a transmitter to manually control the aircraft in case of emergency, during takeoff, for manual checks prior to autonomous flight and during landing. The external pilot communicator relays messages between the external pilot and the ground station.
The flight time for this run was about an hour and 40 minutes.
“It was smooth sailing, the kind of flight we like,” Maxwell said.
In a time of shrinking budgets, the ability to do less with more makes these flights relevant.
“When you have a technique that can limit the time needed to accomplish the same end product, I think that’s very helpful,” Slaughter said.
“It’s saving money and man hours because the type of things that we do would have to be done by people on the ground, and it would take a huge amount of time,” Maxwell said.