Editing NASA Pathfinder (section)

==Pathfinder-Plus==
[[File:Pathfinder Plus solar aircraft over Hawaii.jpg|thumb|Pathfinder-Plus in flight over Hawaii, June 2002, equipped with Skytower communications equipment]]
[[File:20180328 Pathfinder Plus Udvar-Hazy.jpg|thumb|Pathfinder-Plus on display at the [[Udvar-Hazy Center]]]]
During 1998, the Pathfinder was modified into the longer-winged Pathfinder-Plus configuration. It used four of the five sections from the original Pathfinder wing, but substituted a new {{convert|44|ft|m}} long center wing section that incorporated a high-altitude airfoil designed for the follow-on Centurion/Helios. The new section was twice as long as the original, and increased the overall wingspan of the craft from {{convert|98.4|ft|m}} to {{convert|121|ft|m}}. The new center section was topped by more-efficient silicon solar cells developed by [[SunPower|SunPower Corporation]] of [[Sunnyvale, California]], which could convert almost 19 percent of the solar energy they receive to useful electrical energy to power the craft's motors, avionics and communication systems. That compared with about 14 percent efficiency for the older solar arrays that cover most of the surface of the mid- and outer wing panels from the original Pathfinder. Maximum potential power was boosted from about 7,500 watts on Pathfinder to about 12,500 watts on Pathfinder-Plus. The number of electric motors was increased to eight, and the motors used were more powerful units, designed for the follow-on aircraft.<ref name=pathfinderfactold2/>

The Pathfinder-Plus development flights flown at PMRF in the summer of 1998 validated power, aerodynamic, and systems technologies for its successor, the Centurion. On August 6, 1998, Pathfinder-Plus, piloted by Derek Lisoski, proved its design by raising the national altitude record to {{convert|80201|ft|m}} for solar-powered and propeller-driven aircraft.<ref name=heliosfact/><ref>[http://www.naa.aero/html/records/search_resultsguest.cfm?recordNumber=1855 NAA record database] {{webarchive|url=https://web.archive.org/web/20120212230625/http://www.naa.aero/html/records/search_resultsguest.cfm?recordNumber=1855 |date=2012-02-12 }}</ref>

===Atmospheric satellite tests===
In July 2002 Pathfinder-Plus carried commercial communications relay equipment developed by Skytower, Inc., a subsidiary of [[AeroVironment]], in a test of using the aircraft as a broadcast platform. Skytower, in partnership with NASA and the [[Ministry of Internal Affairs and Communications|Japan Ministry of Telecommunications]], tested the concept of an "[[atmospheric satellite]]" by successfully using the aircraft to transmit both an [[High-definition television|HDTV]] signal as well as an [[IMT-2000]] wireless communications signal from {{convert|65000|ft|m}}, giving the aircraft the equivalence of a {{convert|12|mi|km}} tall transmitter tower. Because of the aircraft's high lookdown angle, the transmission utilized only one watt of power, or 1/10,000 of the power required by a terrestrial tower to provide the same signal.<ref name=skytower1>[http://www.ewire.com/display.cfm/Wire_ID/1253 "SkyTower Successfully Tests World's First Commercial Telecom Applications from More Than {{convert|65,000|ft|m}} in the Stratosphere", ''Ewire'', July 22, 2002, accessed September 11, 2008] {{webarchive|url=https://archive.today/20061120200950/http://www.ewire.com/display.cfm/Wire_ID/1253 |date=November 20, 2006 }}</ref> According to Stuart Hindle, Vice President of Strategy & Business Development for SkyTower, "SkyTower platforms are basically geostationary satellites without the time delay." Further, Hindle said that such platforms flying in the stratosphere, as opposed to actual satellites, can achieve much higher levels of frequency use. "A single SkyTower platform can provide over 1,000 times the fixed broadband local access capacity of a geostationary satellite using the same frequency band, on a bytes per second per square mile basis."<ref name=spacecom1>[http://www.space.com/missionlaunches/skytower_020724.html David, Leonard, "Stratospheric Platform Serves As Satellite" Space.com, July 24, 2002, accessed September 11, 2008] {{webarchive|url=https://web.archive.org/web/20080515202902/http://www.space.com/missionlaunches/skytower_020724.html |date=May 15, 2008 }}</ref>

Ray Morgan, president of AeroVironment, has described the concept as, "What we're trying to do is create what we call an 'atmospheric satellite,' which operates and performs many of the functions as a satellite would do in space, but does it very close in, in the atmosphere"<ref name=cnn1>[http://www.cnn.com/TECH/space/9808/07/solar.plane/index.html Knapp, Don. "'Atmospheric satellites' could cut the cost of communications", CNN, August 11, 1998, accessed September 13, 2008]</ref>