Brad Lobitz

The NASA SIERRA science demonstration programme and the role of small-medium unmanned aircraft for earth science investigations

Earth scientists use unmanned aerial vehicles (UAVs) to enable measurements and observations that cannot be collected by manned aircraft such as the ER-2, DC-8 or B-200. Science community interest in UAVs to date has largely been focused on the larger class of UAV such as the Global Hawk and Predator, because of the large mass of legacy airborne science instruments. With the continued miniaturization of instruments and data systems and the rapid pace of development of all classes of UAV world-wide during the past decade, smaller classes of UAV are now capable of providing important science measurements and observations. Small (<50 lbs GTOW) and medium-class UAV (>500 lbs GTOW) complement the larger platforms by enabling in situ measurements of the atmospheric boundary layer with low-altitude remote sensing or air sampling, while providing a relatively low cost platform for storm penetration and dangerous, remote missions where the system may not return. The National Aeronautics and Space Administration (NASA) Sensor Integrated Environmental Remote Research Aircraft (SIERRA) project at the Ames Research Center (ARC) has demonstrated the utility of a medium class unmanned aircraft for providing science measurements in remote and dangerous environments using active, passive and in situ earth science instrument payloads. This article describes the SIERRA project, details past and future missions, and discusses the primary requirements for small and medium class UAV.

Nighttime UAV Vineyard Mission: Challenges of See-and-Avoid in the NAS

A Nighttime UAV Vineyard Mission will demonstrate the use of a UAV-based thermal infrared imaging system for improved direction of frost damage mitigation efforts in agricultural crops. The UAV selected for this April 2005 mission is the APV-3. A flight height of 8,000 ft is planned, enabling thermal mapping coverage of the largest vineyard in California on an hourly basis. To accomplish the Nighttime Mission, it is necessary to demonstrate that the ground-based autopilot has the capability to see-and-avoid potentially conflicting aircraft in the National Airspace System (NAS). This paper provides a review of a daytime UAV test flight conducted in-visual range over the vineyard in August 2003 and describes additional tests being conducted to satisfy FAA see-and-avoid requirements for the planned out-of-visual range nighttime mission.

Surface reflectance mapping using interferometric spectral imagery from a remotely piloted aircraft

During October 1997, NASAs Environmental Research Aircraft and Sensor Technology (ERAST) Program conducted flight tests of the Pathfinder Remotely Piloted Aircraft (RPA) out of the Pacific Missile Range Facility (PMRF), Kauai (Hawaii). The Pathfinder was a light-weight (=500 lb), solar-powered RPA with an extremely limited (=35 lb) sensor payload capacity. One of the ERAST objectives was to evaluate the feasibility of using such RPA platforms to collect remotely sensed data in support of Earth systems science. A key aspect of this objective was to make simultaneous spectral measurements of a common target using an airborne spectral imager and a ground-based spectrometer. Intercomparison of these results, together with modeling of atmospheric radiative effects, enable the establishment of ground-truth and the verification of the spectral imagers radiometric calibration. The outcome of this calibration exercise is a procedure for deriving the surface albedo for a variety of different regions of the overall scene containing the ground-truth target. A Digital Array Scanned Interferometer (DASI) hyperspectral imager jointly developed by NASA Ames Research Center and and Washington University was selected as the imaging spectrometer payload. Compactness, light weight, low power draw, rugged design and simplicity of operation made the DASI an ideal candidate for this mission.