NASA - Coffee harvest optimization using Pathfinder-Plus (solar-powered aircraft)

Coffee is the leading agricultural commodity traded on world markets, and Hawaiian coffee is considered by many to be some of the finest in the world. A key to producing excellent coffee is knowing the right time to harvest it.

A NASA research mission will use an aircraft, known as an "Uninhabited Aerial Vehicle" or "UAV" to aid Hawaiian coffee growers by providing the growers with spectral (or color) images of their crops. From this information the growers will know, down to the exact day, the best time for harvesting the coffee, thereby bringing the best possible flavor to consumers. Image acquisition will be conducted over the 3,600-acre Kauai Coffee Plantation (KCP) on the island of Kauai, Hawaii.

Imagery from two digital camera systems will be analyzed to determine coffee field ripeness and to identify any drip irrigation problems and weed proliferation.

In September and October 2002, NASA’s solar-powered UAV Pathfinder-Plus aircraft will collect imagery over KCP, the largest coffee concern in the United States. Researchers hope the remotely piloted aircraft's unique capabilities to "loiter" for long periods over crop fields will provide data that coffee growers can use to select the best times to harvest coffee "cherries" located in areas of their plantation that ripen at different rates. At KCP, the dominant variety ripens to a yellow color.

The lightweight flying wing, Pathfinder-Plus, will operate from the U.S. Navy's Pacific Missile Range Facility (PMRF) at Barking Sands on the Hawaiian island of Kauai.

KCP was selected as a test site for the UAV demonstration because of its large scale of production (4-5 million pounds/year) and because of its close proximity to PMRF.

Traditionally, coffee has been cultivated on small, one to 100-acre farms where hand picking is the standard harvesting procedure. However, KCP uses a fleet of mechanical harvesters. This approach is becoming a global trend in coffee production. Mechanical harvesters dislodge coffee ‘cherries’ at all stages of ripening. Ripe coffee cherries have the highest commercial value, commanding a significantly higher price per pound than either unripe or overripe cherries. The challenge for large-scale mechanical harvesting operations is dispatching the harvesters to the ripest fields in order to optimize the harvest of this high-value crop.

Part of NASA's UAV-based science demonstration program, these flights will show the ability of this type of aircraft to carry Earth-viewing scientific payloads in long-duration missions.

Professor Herwitz of Clark University, AeroVironment and NASA are participants in the UAV Coffee Project that was established in 2001 under a grant from NASA's Earth Science Enterprise. Herwitz leads the project. NASA funds the program with $3.76 million grant. AeroVironment, Inc., Monrovia, Calif., built the Pathfinder-Plus aircraft that will fly the demonstration mission.

The coffee mission is one of two projects selected from 45 proposals received in response to a solicitation issued by NASA in 2000. The solicitation requires that principal investigators manage the missions. Each mission's lead investigator is responsible for choosing the UAV best suited for the experiment, and then managing all aspects of the mission for NASA. The agency has slated about $8 million to fund two UAV missions during four years.

The coffee mission is part of NASA's Earth Science Enterprise, a long-term research effort aimed at understanding how human-induced and natural changes affect our global environment, while providing practical societal benefits to America today. The Earth Science Enterprise provides the sound science needed by policy and economic decision makers to assure responsible stewardship of the global environment.

Imaging payloads are housed in environmental pods developed by NASA Ames Research Center in California’s Silicon Valley for previous missions of the prototype Pathfinder UAV. Images will be downlinked in near-real time for viewing. Two commercial, off-the-shelf, high-resolution digital camera systems were purchased and interfaced for airborne operation.

With the assistance of New Mexico State University, an application for a Certificate of Authorization (COA) to fly the Pathfinder Plus in national airspace (NAS) was prepared and submitted to the Federal Aviation Administration (FAA) Western Regional Office. Honolulu air traffic controllers will monitor the mission in NAS. An agreement among Clark University, the FAA Honolulu Control Facility and the Pacific Missile Range Facility establishes responsibilities and defines procedures for the aircraft’s operation in NAS.

The UAV Coffee Project will test new practices in remote aerial imaging and analysis, wireless Ethernet ‘bridge’ communications technology and commercial capabilities of UAV technologies. Data from the cameras attached to the UAV will be continuously downloaded to computers that coffee growers can monitor and will indicate which parts of the plantation are ready for harvesting.

The use of remote-sensing technology to monitor the Earth's surface is not new. Satellites orbiting the Earth currently provide remotely sensed data, but they focus on large areas of the planet’s surface. Aerial photography obtained by on-board pilots has been available for decades, but it is expensive. What is new in Herwitz's research is the platform -- the UAV -- on which the digital cameras are mounted. The UAV promises several advantages over other platforms. It requires no on-board pilot and can fly at low altitudes targeting only the portion of the Earth's surface under study.

The aircraft, because it is solar-powered, eliminates expensive fuel costs. In the future, researchers envision that the airplane will be able to ‘loiter’ in the air over the region of interest for days or weeks at a time, or until weather conditions are best for data gathering.

The coffee plantation provides an ideal laboratory for the demonstration. If it succeeds, the project not only will pave the way for agricultural decision-making via UAV, but it will show the practicality of UAV flights to support users who need real-time, high-resolution imaging in a hurry. UAV image/data collecting missions could be helpful in fighting forest fires, evaluating environmental change or assessing civil emergency responses.

Herwitz collected and analyzed preliminary airborne images of the Kauai Coffee Plantation. These images revealed previously unrecognized sites of fungal disease, vine proliferation and irrigation problems. He soon recognized the potential of airborne monitoring of the fields during the harvest season.

The digital camera systems acquired for the current UAV Coffee Project were tested using a piloted, twin-engine aircraft over flower plantations in Gilroy, Calif., in July and August 2001. The tests verified that the camera systems operated as required under manual control.

Additional payload test flights were conducted using a piloted, fixed-wing, twin-engine aircraft in October 2001 over southern Kauai. The objective was to test new commercial ‘off-the-shelf’ wireless technology that could improve the performance and significantly reduce the cost of line-of-sight telemetry for imaging payloads on UAVs.

The project team identified an Ethernet bridge as having the capability of connecting two or more networks through a line-of-sight wireless, high-speed data link. This wireless, bi-directional communication system was originally designed for spatially fixed wireless building-to-building links with separation distances of 25 miles. The study tested the Ethernet bridge’s capability to function as a command-and-control system on a mobile airborne platform. It was configured for remote payload control and transmission of acquired imagery to a ground station.

The airborne side of the Ethernet bridge served as the link between the airborne system payload computer and an omni-directional stub antenna positioned on the underside of the aircraft. The ground-based side of the bridge was equipped with an omni-directional ‘rubber duck’ antenna and served as the link to a portable laptop computer. The ground-based payload operator controlled each camera system remotely using the laptop computer.

Operational bi-directional Ethernet connectivity enabled the team to control the airborne high-resolution digital camera system through a ground-based computer. The connectivity also was used for downlinking image files during flight. The team successfully demonstrated the performance of low-cost, commercial, off-the-shelf components.

Five flight tests were conducted at 9,900 feet altitude over southern Kauai on separate days from Oct. 6-13, 2001. The objectives were to further test camera operation, to test the telemetry system, and to collect imagery for subsequent use in algorithm development. During the first two flights, an operator aboard a Piper Navajo airplane operated the imaging payload wirelessly, and images were successfully transferred to an operator’s laptop computer. During the last three flights, a series of tests was conducted with remote operation of the payload from the ground. The ground antenna was positioned on a ridge at 990-foot elevation approximately 2 miles north of the flight lines.

Continuous broadband wireless Ethernet connectivity was successfully established between the moving aircraft-based local area network (LAN) and the fixed ground control station LAN. Error-free 16-megabyte (MB) digital images, with no data dropouts, were transmitted to the ground-based laptop computer at transfer rates ranging from 1 to 4 Mbit per second. For 16 MB images, these transfer rates represent transfer times ranging from one-half minute to 3 minutes as a function of distance. At a distance of 6.8 miles with the data transmit rate exceeding 2 Mbit per second, an acquired image was transmitted in less than 25 seconds.

Team members integrated the imaging payloads onto the Pathfinder Plus aircraft from October 2001 to March 2002. These payloads were downsized and integrated into the environmental instrument pods.

The ERAST program is a joint NASA-industry initiative to develop and demonstrate aeronautical technologies that could lead to a family of remotely or autonomously operated UAVs to carry out long-duration Earth science and environmental missions at high altitudes. A concurrent ERAST effort is the development, miniaturization and integration of special-purpose sensors and imaging equipment for UAVs.

Begun in late 1993, the ERAST technology demonstration project is managed by NASA's Dryden Flight Research Center, Edwards, Calif., with significant contributions from NASA Ames, NASA Langley Research Center, Hampton, Va., and NASA Glenn Research Center, Cleveland, Ohio. The project is a joint NASA-industry alliance under a joint sponsored research agreement. A number of small companies are members of the ERAST alliance.

NASA is working with the FAA on the long-term issues related to operations of these vehicles in the national airspace and developing technology such as ‘see and avoid’ sensors/processors and over-the-horizon communications equipment to make operations in civil airspace practical.

UAVs offer great promise to meet the needs of both science and industry for airborne sensing and imaging in a cost-effective manner while alleviating the constraints of mission duration, altitude and flight over inhospitable terrain faced by aircraft with on-board crew. Such long-duration, high-altitude UAVs can be flown on upper-atmospheric science missions to collect data and images that could help scientists identify and monitor environmental and climatic changes. These aircraft also could carry telecommunications equipment to high altitudes, serving much like satellites for a fraction of the cost of putting a traditional satellite into space.

The 98-foot-wingspan Pathfinder set unofficial world altitude records in 1997 for propeller-driven aircraft. Later, the larger Pathfinder-Plus, with a wingspan of about 125 feet, flew to an altitude of 80,201 feet in mid-1998. The Helios Prototype also set a new world altitude record for non-rocket-powered aircraft of 96,863 feet on Aug. 13, 2001.

Pathfinder was one of several prototypes under study by NASA's ERAST program. Pathfinder was a remotely controlled, solar-powered flying wing, designed and built as a proof-of-concept vehicle for a much larger aircraft capable of flying at extremely high altitudes for weeks at a time. It was built by AeroVironment, Inc., a California company that developed the human-powered Gossamer Condor and Gossamer Albatross lightweight aircraft during the 1970s, and later made the solar-electric powered Gossamer Penguin and Solar Challenger.

The basic configuration and concepts for Pathfinder were first realized with the High Altitude Solar (HALSOL) aircraft, built in 1983 by AeroVironment and the Lawrence Livermore Laboratory, Livermore, Calif. Pathfinder was constructed of advanced composites, plastics and foam, and despite a wingspan of nearly 100 feet, it weighed only about 600 pounds.

After flights over the Kauai Coffee Company plantation, the largest coffee plantation in the United States, the research team led by Herwitz will brief coffee industry officials on its findings. The mission will allow NASA to provide sound science to a multi-billion- dollar American industry. This demonstration is just one potential agricultural-management application using UAVs.

Future: NASA and AeroVironment engineers currently are working to extend stratospheric flight time of solar-powered aircraft to durations exceeding two weeks, and eventually up to six months.

In the summer of 2003, a 72-hour mission is planned for NASA’s solar-powered UAV Helios built by AeroVironment, Inc. The slow flight speed and loitering capability of this airframe has potential for airborne remote sensing of Kauai.

Still photographs of the Pathfinder Plus carrying a payload on an earlier, non-coffee mission are available from the NASA Dryden Flight Research Center Internet Web site photo gallery at: www.dfrc.nasa.gov/gallery/photo/Pathfinder-Plus/index.html