Integrated Sensor is Structure

{{Short description|Military research program}}

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The Integrated Sensor is Structure (ISIS) was a program managed by the United States Air Force (USAF) Research Laboratory to research the feasibility of using an unmanned airship as a high-altitude aerial reconnaissance and surveillance platform. It is sometimes called Integrated Sensor is the Structure, as a fundamental innovation was the use of the airship structure as the sensing component of a state-of-the-art radar system.

In 2006, contracts were awarded to Raytheon for development of a large-area, light, Active electronically scanned array antenna which could be bonded to the structure of a blimp,{{cite web | date = 8 August 2006 | url = http://investor.raytheon.com/phoenix.zhtml?c=84193&p=irol-newsArticle&ID=893481 | title = DARPA Asks Raytheon to Develop Radar for 'Integrated Sensor Is Structure' Program}} Northrop Grumman for antenna development, and Lockheed Martin for development of the airship.{{cite web | last = Singer | first = Jeremy | date = August 9, 2006 | url = http://www.nbcnews.com/id/14275624 | archive-url = https://web.archive.org/web/20161230074804/http://www.nbcnews.com/id/14275624/ | url-status = dead | archive-date = December 30, 2016 | title = Pentagon's airship plans are up in the air | format = | work = NBC News | accessdate = 16 March 2009 }} As proposed, the {{convert|450|ft|m|adj=on}}-long surveillance airship could be launched from the US and stationed for up to 10 years at an altitude of {{convert|65000|ft|m}}, observing the movement of vehicles, aircraft, and people below.{{cite news|title=ISIS on Station|url=http://www.codeonemagazine.com/images/C1_Vol24_No3_new_1271449318_8621.pdf|accessdate=19 July 2017|work=Code One Magazine|issue=3|publisher=Lockheed Martin|date=2009|volume=24 }} At that altitude, the airship would be beyond the range of most surface-to-air and air-to-air missiles. The airship would be filled with helium and powered, at least in part, by solar-powered hydrogen fuel cells.

On March 12, 2009, the USAF announced that it had budgeted $400 million for work on ISIS .{{cite web| last = Barnes | first = Julian E. | date = March 13, 2009

| url = http://www.latimes.com/news/nationworld/nation/la-na-spyblimp13-2009mar13,0,4608400.story | title = Pentagon Plans Blimp To Spy From New Heights | format = Newspaper article | work = Los Angeles Times | accessdate = 16 March 2009}} In April 2009, DARPA awarded a $399.9 million contract to Lockheed Martin as the systems integrator and Raytheon as the radar developer for phase three of the project: the construction of a one-third scale model, which would remain in the air for up to a year.{{cite web| last = Ratnam | first = Gopal | date = April 27, 2009 | url = https://www.bloomberg.com/apps/news?pid=20601103&sid=aoMByt6gSFj8&refer=news | title = Lockheed Gets $399.9 Million Pentagon Order For Blimp | work = Bloomberg L.P. | accessdate = 28 April 2009}} The ultimate goal was to provide radar capable of delivering persistent, wide-area surveillance tracking and engagement of air targets within a 600-kilometer area and ground targets within a {{convert|300|mi|km|adj=on}} area, according to DARPA. The model blimp was to have radar coverage of about 7,176 square yards (6,000 square meters) and be tested at an altitude of {{convert|6|mi|km}} above the ground. The contract initially awarded $100 million to the two companies, with the rest to follow in phases, with a completion date of March 2013.

As of 2012, the development of the airframe had been delayed to focus on "radar risk reduction".{{cite news|last1=Warwick|first1=Graham|title=Airship Programs – Not So Buoyant, Says GAO|url=http://aviationweek.com/blog/airship-programs-not-so-buoyant-says-gao|accessdate=6 February 2020|url-status=dead|archiveurl=https://web.archive.org/web/20150714215038/http://aviationweek.com/blog/airship-programs-not-so-buoyant-says-gao|archivedate=14 July 2015}} The United States Department of Defense ended the program in 2015. $471 million had been spent from 2007 through 2012.{{cite journal|last1=d’Oliveira|first1=Flavio Araripe|last2=de Melo|first2=Francisco Cristovão Lourenço|last3=Devezas|first3=Tessaleno Campos|title=High-Altitude Platforms — Present Situation and Technology Trends|journal=Journal of Aerospace Technology and Management|date=July 2016|volume=8|issue=3|page=254|doi=10.5028/jatm.v8i3.699 |url=http://www.redalyc.org/html/3094/309446752001/|accessdate=19 July 2017|doi-access=free}}