## 2 UAS Platform Types and Characteristics
### Characteristics and Examples of UAS Categories
#### 2.2.5. HALE UAS  
High Altitude, Long Endurance UAS platforms are a more recent introduction into the UAS world. Outside of the US Department of Defense, the major civilian components that have employed HALE UAS to support science have been NASA and the US National Oceanographic and Atmospheric Administration (NOAA). Their driving scientific objectives necessitate the use of HALE platforms to collect information at regional and global scales to allow assessments of climate variable impacts across broad regions of the globe and to support satellite observations at spatial and temporal scales, not achievable with less capable manned or unmanned platforms. Therefore, the platforms identified in this section are primarily those operated by NASA in collaboration with other agencies. These platforms have stepped beyond the experimental stage and are now, in some cases, employed operationally (e.g., Global Hawk) to support remote sensing collection and earth/atmospheric science investigations. Because of their operational uniqueness and capabilities, these platforms are prohibitively expensive for most users; they are therefore used to support large investigative science campaigns, rather than smaller, localized assessments where other categories of UAS or manned platforms prove more cost-effective. In the 1990s, a joint NASA-industry initiative (ERAST) to validate the capabilities of UAS to fly operational science missions was undertaken. One of the program goals was to develop UAS operational capabilities of ~30,000m feet altitude and >24-h duration. During the program efforts, the following milestones were achieved:  
* Sustained flight above 16,700 m for four hours by the Altus UAS in 1999 after being equipped with a powerful turbocharger;
* An altitude of over 17,000 m achieved by the Perseus B in 1998, an unofficial record for a turbocharged single-engine, propeller-driven craft;
* An altitude of 24,460 m achieved by the Pathfinder-Plus in August 1998, a world record for both propeller-driven and solar-powered aircraft. * An unofficial world-record altitude of 29,543 m achieved by the Helios Prototype in August, 2001, more than two miles higher than any non-rocket powered aircraft had ever flown. * A follow-on NASA-supported endeavor, the UAV Science Demonstration Program (UAV-SDP) led to a successful crop, forest and coral reef imaging science demonstrations mission by the Pathfinder over the Hawaiian island of Kauai in 1997 (Figure 10). A more recent HALE UAS platform development is the Northrup-Grumman Global Hawk (Figure 11). NASA and NOAA have collaborated to utilize the Global Hawk UAS to support a number of scientific remote sensing campaigns since 2008. The Global Hawk has an operating altitude of 19,800 m and a flight endurance of over 30 h. The NASA Global Hawk cruises at 550 km/h and carries a payload of 750 kg for a range of over 17,000 km. The platform has compartments that can house over 10 different instruments, supporting multiple science instrumentation measurement capabilities. Figure 10: The Pathfinder HALE UAS. Image Courtesy NASA. The 2010 Global Hawk Pacific Mission (GloPac) campaign was the first NASA Earth Science campaign to be conducted on the aircraft. Ten instruments were installed in the HALE UAS to support measurements of trace gases, aerosols and dynamics of the upper troposphere and lower stratosphere. The instrumentation also supported validation efforts of the instruments aboard the NASA Aura and CALIPSO earth-monitoring satellite. The Genesis and Rapid Intensification Process (GRIP) hurricane surveillance mission's purpose was to better understand how tropical storms form and develop into major hurricanes. This campaign was conducted to capitalize on a number of ground networks, airborne science platforms, and space-based assets.