1 June 2005
Solar-powered airplane with cameras and wireless local area network (WLAN)
NASA's Pathfinder-Plus UAV is a remote sensing platform.
Unmanned aerial vehicle (UAV) capabilities are evolving rapidly, from both technical and regulatory standpoints.
It is likely that these platforms will begin to offer new alternatives for agricultural users, security providers, and others needing high spatial resolution digital imagery acquired and delivered in near-real time.
Pathfinder-Plus is a lightweight flying wing equipped with eight solar-electric motors. The aircraft is an enlarged version of the initial Pathfinder UAV, which established a world altitude record(>21 km) for propeller-driven aircraft.
During a subsequent, lower-altitude mission, NASA demonstrated the use of Pathfinder for image collection with multispectral and hyperspectral digital instruments over land areas and coastal zone waters.
The main attraction of this class of aircraft for certain monitoring and surveillance missions is their slow flight speed (generally <50 km hr-1, depending on wind conditions) and hence their ability to loiter over localized areas for extended periods.
Payload camera imager
On an initial proof of concept mission over a coffee plantation in Hawaii, two complementary digital camera systems were on board for remote operation within the UAV weight (68 kg) and power (500 W) limitations.
A color high-resolution camera collected photos for qualitative interpretation, and a narrow-band multispectral imager explored automated spectral analysis of canopy color in relationship to crop ripeness.
The Kodak data system incorporated a commercial off-the-shelf design philosophy involving use of the Windows XP operating system and included a micro AT motherboard computer system with integrated drive electronics disk interface and an IEEE 1394 high-speed serial camera interface.
Other system components included a data logger for recording payload pod temperature, pressure, and relative humidity, a serial-to-Ethernet converter, and an Ethernet hub.
The operator interface revolved around the use of PCAnywhere software (Symantec Corp.), permitting the operator to access the flight computer by wireless Ethernet and remotely execute vendor software for camera and data logger operation.
The DuncanTech instrument grew on a highly customized RedHat Linux operating system, which supported three network interfaces, two IP over Ethernet, and one PPP over serial. A menu-driven interface was a part of the rig, requiring transfer of only a few ASCII characters to control the instrument.
A line-of-sight local area network (LOS-LAN) based on commercially available wireless hardware was configured for both camera control and data download.
To avoid cross-talk interference, bridges configured to operate at opposite ends of the unlicensed IEEE 802.11b frequency spectrum.
A wide area network (WAN) enabled UAV tracking and longer-range command and control. Tracking took place deterministically using GPS information collected by a receiver incorporated into the system.
The project successfully demonstrated the safe and effective use of a loitering UAV for collection of commercial agricultural imagery. UAVs will play an expanded role, complementary to that of satellites and conventionally piloted aircraft, for agricultural support.
Further, loitering UAVs may provide image support to user communities in disaster relief, fire management, and homeland security.
Nicholas Sheble (nsheble@isa.org) edits the Sensors department.
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