Unmanned Aircraft Systems (UAS) have evolved rapidly over the past decade driven primarily by military uses, and have begun finding application among civilian users for earth sensing reconnaissance and scientific data collection purposes. Among UAS, promising characteristics are long flight duration, improved mission safety, flight repeatability due to improving autopilots, and reduced operational costs when compared to manned aircraft. The potential advantages of an unmanned platform, however, depend on many factors, such as aircraft, sensor types, mission objectives, and the current UAS regulatory requirements for operations of the particular platform. The regulations concerning UAS operation are still in the early development stages and currently present significant barriers to entry for scientific users. In this article we describe a variety of platforms, as well as sensor capabilities, and identify advantages of each as relevant to the demands of users in the scientific research sector. We also briefly discuss the current state of regulations affecting UAS operations, with the purpose of informing the scientific community about this developing technology whose potential for revolutionizing natural science observations is similar to those transformations that GIS and GPS brought to the community two decades ago.

No abstract

Low‐level helicopter flights were used to collect samples of smoke from burning chaparral in southern California and over a boreal forest fire in northern Ontario, Canada. The smoke plume samples were analyzed for carbon dioxide (CO2), carbon monoxide (CO), hydrogen (H2), methane (CH4), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N2O). Samples of gas were also analyzed from upwind of the burns to determine the ambient background levels. CO2‐normalized emission ratios (ΔX/ΔCO2; where X is equal to each gas; vol/vol) were determined for each trace gas for conditions of flaming, mixed, and smoldering combustion. The emission ratios for these trace gases were found highest during smoldering combustion, generally thought to be the least efficient combustion stage. However, indications that high emission ratios for these trace gases can be produced during very vigorous flaming combustion are also indicated by our results. Whether this results from quenching processes due to rapid entrainment of air or from localized pockets of oxygen‐depleted air, or both, deserves further study. Emission ratios determined for ethane (C2H6), ethylene (C2H4), propane (C3H8), and propylene (C3H6), obtained over an earlier chaparral fire at the same approximate site, are presented for the first time. While emission ratios for these hydrocarbons ranged from a factor of 15 to 100 less than their corresponding methane emission ratios, they strongly supported the production of highly reduced trace gases during vigorously flaming combustion; that is, ethylene was generated in higher proportion than ethane, and propylene in higher proportion than propane.

No abstract