## 2 UAS Platform Types and Characteristics
### Classification of UAS Platforms  
Classification of UAS platforms for civil scientific uses has generally followed existing military descriptions of the platforms based upon characteristics such as size, flight endurance, and capabilities (Figure 1). The generally accepted class nomenclature in the civilian realm is as follows:  
**MAV (Micro (or Miniature) or NAV (Nano) Air Vehicles):** are so called because of their size, which typically enables military versions of these aircraft to be transported within individual soldiers' backpacks. These aircraft tend to operate at very low altitudes (\(<\)330 m), with size limitations on battery capacity leading to short flight times in the vicinity of _ca_. 5-30 min.  
**VTOL (Vertical Take-Off & Landing):** These aircraft require no takeoff or landing run, and are therefore typically chosen in situations where limitations of terrain require this specialized capability. Aircraft of this type operate at varying altitudes depending on their mission profile, but predominantly fly at low altitudes. High power requirements for hovering flight limit the flight durations for VTOLs, except in the largest sizes where increased lifting capabilities accommodate large fuel capacity.  
**LASE (Low Altitude, Short-Endurance):** systems, also known as **sUAS, small unmanned aircraft systems**, also obviate the need for runways with aircraft optimized for easy field deployment/recovery and transport. The aircraft component of these systems typically weighs _ca_. 2-5 kg,with wingspans \(<\)3 m to enable launching from miniature catapult systems, or by hand. Compromises between weight and capability tend to reduce endurance and communication ranges to 1-2 h and within a few km of ground stations.  
**LASE Close:** This category describes small UAS whose aircraft do require runways, but whose larger size and weight confer increased capabilities. These systems operate at up to ca. 1,500 m altitude and may remain aloft for multiple hours, although these limits have been substantially exceeded by specially-modified \"record-breaker\" aircraft.  
**LALE (Low Altitude, Long Endurance):** Typically at the upper end of the \"sUAS\" weight designation by the United States Federal Aviation Administration (FAA; see below), these UAS may carry payloads of several kg at altitudes of a few thousand meters for extended periods.  
**MALE (Medium Altitude, Long Endurance):** aircraft are typically much larger than low-altitude classes of UAVs, operating at altitudes up to _ca._ 9,000 m on flights hundreds of km from their ground stations lasting many hours.  
**HALE (High Altitude, Long Endurance):** These are the largest and most complex of the UAS, with aircraft larger than many general-aviation manned aircraft. These UAVs may fly at altitudes of 20,000 m or more on missions that extend thousands of km. Some HALE aircraft have flight durations over 30 h, and have set records for altitude and flight duration.  
Figure 1: Image courtesy of US Department of Homeland Security [7].  
For the purposes of simplicity we will describe some characteristics of the various size platforms for supporting civilian remote sensing and scientific research applications from the former identified categories of UAS (MAV, LALE, LASE, MALE, HALE, and VTOL).