Military radar in Massachusetts, which is used by NORAD’s Northeast Air Defense Sector (NEADS), is out of use this morning in order to undergo maintenance work. [9/11 Commission, 10/27/2003 
; 9/11 Commission, 10/27/2003 ]
Radar Scheduled to Go Down – The J53 radar in North Truro, Massachusetts, is one of a number of radar sites that NEADS receives data from. [United States Space Command, 12/30/1995; Jane’s C4I Systems, 9/1/2005; North American Aerospace Defense Command, 10/23/2006 ] It has a range of 250 miles. According to Technical Sergeant Jeffrey Richmond, the assistant air surveillance technician at NEADS, J53 is scheduled to go down this morning for some major repairs to be carried out. [9/11 Commission, 10/27/2003 ; 9/11 Commission, 10/27/2003 ]
NEADS Personnel Refer to Radar – A member of staff at NEADS apparently refers to the J53 radar being offline shortly after those on the NEADS operations floor learn of the Flight 11 hijacking (see (8:38 a.m.) September 11, 2001) and while they are trying to locate the hijacked aircraft. She mentions that NEADS technicians “still should be able to get it” (presumably referring to the plane’s radar track) “without 53.” [North American Aerospace Defense Command, 9/11/2001] (According to Richmond, the area covered by J53 is overlapped by other radars, “so the need for radar to undergo routine maintenance is accounted for.”) ID technician Shelley Watson will later recall that the NEADS ID desk uses the J53 radar as a point from which it attempts to locate Flight 11. At some time during the morning, Richmond insists that J53 be put back online at some capacity. Whether this happens is unstated. [9/11 Commission, 10/27/2003 ; 9/11 Commission, 10/27/2003 ]
Radar Part of ‘Joint Surveillance System’ – The J53 radar site is part of the Joint Surveillance System (JSS). [Transportation Safety Board of Canada, 9/2/1998; US Department of the Air Force, 11/1/1999 ; 9/11 Commission, 2004] The JSS consists of “long-range radar sites around the perimeter of the US, with data shared by the [Department of Defense], FAA, Customs, and others.” A 2003 Department of Defense report will state that, at the time of the 9/11 attacks, US air defense relies “largely on outward looking ground-based radars, specifically, the Joint Surveillance System.” [US Department of Defense, 7/2003 ] According to General Ralph Eberhart, the commander of NORAD, NORAD has access to the JSS, “which is that system that rings the United States and looks out.” He will say this system “looks for that foreign threat. It looks for someone coming into our airspace that’s not authorized.” [US Congress. Senate, 10/25/2001]
9:34 a.m. September 11, 2001: NEADS Surveillance Technicians Instructed to Remove Simulated Information from Radar Screens
A technician at NORAD’s Northeast Air Defense Sector (NEADS) instructs personnel on the NEADS operations floor to turn off their “sim switches,” apparently so as to remove from their radar screens simulated information for a training exercise that was being conducted this morning. [Northeast Air Defense Sector, 8/23/2001; North American Aerospace Defense Command, 9/11/2001; 9/11 Commission, 2004]
Staffer Complained, ‘Let’s Get Rid of This Goddamn Sim’ – A few minutes earlier, at 9:30 a.m., a member of staff on the operations floor complained about simulated information—presumably false tracks—appearing on NEADS radar screens. He said: “You know what, let’s get rid of this godd_mn sim. Turn your sim switches off. Let’s get rid of that crap.” [North American Aerospace Defense Command, 9/11/2001; North American Aerospace Defense Command, 9/11/2001] (A “sim switch” presumably allows simulated material on radar scopes to be turned on or off.)
Technician Instructs, ‘Turn Off Your Sim Switches’ – Now a member of NEADS staff, who according to a 9/11 Commission document is Technical Sergeant Jeffrey Richmond, gives an instruction to the NEADS surveillance technicians, “All surveillance, turn off your sim switches.” Seconds later, apparently in response to this instruction, someone on the operations floor tells a colleague, “You got your sim switches down.” [North American Aerospace Defense Command, 9/11/2001; 9/11 Commission, 2004]
Sim Switches Turned On for Day’s Exercise – Simulated material (“sim”) is apparently appearing on NEADS radar screens because of the NORAD training exercise, Vigilant Guardian, that was being conducted this morning (see (6:30 a.m.) September 11, 2001). Former Deputy Secretary of Defense John Hamre has revealed that NORAD has the capacity to inject simulated material into the system, “as though it was being sensed for the first time by a radar site.” In a training exercise in December 1998, for example, NORAD ran “30 different simulations, some of them being mass attacks, some of them being single missiles.” An information page on the current exercise stated, “All of NEADS, operations personnel are to have their sim switches turned ‘on’ starting at 1400Z 6 Sept. 01 till endex [the end date of the exercise].” Since Vigilant Guardian was originally scheduled to continue until September 13, this would mean NEADS personnel had their sim switches turned on this morning. [US Department of Defense, 1/15/1999; Northeast Air Defense Sector, 8/23/2001]
Radar Equipment Set to Display ‘Sim Tracks’ – A memo outlining special instructions for Vigilant Guardian participants further detailed how NORAD equipment needed to be set to display simulated material during the exercise. It stated: “The exercise will be conducted sim over live on the air sovereignty string. The Q-93 must be placed in the mixed mode to allow the telling [i.e. the communicating of information between facilities] of sim tracks.” [Northeast Air Defense Sector, 8/23/2001] The Q-93 is a piece of equipment used by NORAD, which is described as “a suite of computers and peripheral equipment configured to receive plot data from ground radar systems,” and which “performs track processing.” [General Accounting Office, 12/24/1992 ; Federation of American Scientists, 4/23/2000] The Q-93 also “receives flight plans from the FAA, and has bi-directional communications with NORAD headquarters and a real-time link to AWACS [Airborne Warning and Control System planes].” [Satterthwaite, Corman, and Herm, 6/2002]
Exercise Supposedly Canceled Earlier On – While NEADS radar scopes are still displaying simulated material as late as 9:34 a.m., some accounts will claim the Vigilant Guardian exercise was canceled shortly after 9:03 a.m., when the second World Trade Center tower was hit (see (Shortly After 9:03 a.m.) September 11, 2001). [Airman, 3/2002; Filson, 2003, pp. 59] And according to a report in the Toronto Star, “Any simulated information” for the exercise was “purged from the [radar] screens” at NORAD’s operations center in Cheyenne Mountain, Colorado, shortly before the second WTC tower was hit (see (9:00 a.m.) September 11, 2001). [Toronto Star, 12/9/2001] However, NEADS will receive a phone call from the operations center at 10:12 a.m. in which the caller asks it to “terminate all exercise inputs coming into Cheyenne Mountain” (see 10:12 a.m. September 11, 2001). [North American Aerospace Defense Command, 9/11/2001]
