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 ( < 550 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.