Operation RANGER

Note: For information related to claims, call the Department of Veterans Affairs (VA) at 800-827-1000 or 

the Department of Justice (DOJ) at 800-729-7327. For all other information, call the Nuclear Test 

Personnel Review (NTPR) Program at 800-462-3683.

Operation RANGER, the first series of atmospheric nuclear tests conducted by the Atomic Energy 

Commission (AEC) at the Nevada Proving Ground (NPG), consisted of five detonations, all of which were 

airdrops. The operation also included one non-nuclear high-explosive test detonated 2 days before the first 

nuclear test. RANGER lasted from January 27 to February 6, 1951, and involved approximately 

770 Department of Defense (DOD) participants in air support services, scientific projects, weather support, 

communications security, and observer activities. The series was intended to provide data for use in 

determining design criteria for nuclear devices scheduled for detonation at Operation GREENHOUSE, to be 

conducted at the Pacific Proving Ground from April 7 to May 24, 1951.

Historical Background

Since RANGER was only a 13-day operation, the same units and participants performed the same duties 

throughout the series. The majority of DOD personnel at RANGER took part in the air support services 

provided by the Air Support Section of the Test Group. Air Force personnel from the Special Weapons 

Command (SWC) and Headquarters, U.S. Air Force, conducted most of these activities. At each test, air 

support activities included the airdrop of the nuclear device, cloud sampling, cloud tracking, aerial surveys of 

the terrain, and courier service. Air Force personnel also provided meteorological services and 

communications security and monitored worldwide radioactivity from the RANGER tests for the Atomic Energy 

Detection System.

Air Force participation at the RANGER shots involved personnel from:

• Headquarters, U.S. Air Force

• Air Research and Development Command

• Air Training Command

• Strategic Air Command

• Air Force Security Service

• Air Weather Service

• Air Force Cambridge Research Laboratory

• 4901st Support Wing (Atomic) (SWC)

• 4925th Special Weapons Group (SWC)

• 374th Reconnaissance Squadron (Very Long Range) Weather

• 1009th Special Weapons Squadron.
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Primary Army participation came from the 82nd Reconnaissance Battalion from Fort Hood, Texas, which 

provided security at the test site.

The Scientific Tests Section of the Test Group administered projects at each nuclear detonation. DOD

personnel were involved in eight projects at each shot except BAKER, where they took part in seven 

experiments. Of the 12 known DOD participants, 6 were from the Army Participation Group, an organization 

representing the Chief, Armed Forces Special Weapons Project. The other six were officers from the Army, 

Navy, and Air Force. Participants in these scientific experiments placed film badges, fabrics, and other 

materials and instruments in or around military fortifications constructed in the ground zero area. They 

retrieved the equipment after the detonation, when radiation levels had decreased and limited access into the 

shot area was permitted.

The number of observers at RANGER has been documented as 156, but only 3 of these are believed to have 

been military personnel.

Summary of Operation RANGER Nuclear Weapons Tests

The accompanying table details specific information for each nuclear shot in the RANGER series, and the 

accompanying map shows ground zero and the operations area. These five shots were of the same type, 

were detonated at the same site, and involved similar activities. Shot FOX, the last detonation, was the largest 

shot and the only test not detonated on schedule. A one-day postponement was caused by an oil leak in the 

B-50 drop aircraft. Fired 1,435 feet above Frenchman Flat, Shot FOX had a yield of 22 kilotons. The initial 

radiation survey, conducted about one hour after the detonation, showed a maximum gamma intensity of 

15.5 roentgens per hour (R/h) at ground zero and 8.0 R/h about 200 meters from ground zero. At 900 meters, 

the radiation level decreased to 0.25 R/h.

Radiation Protection Standards

The AEC established safety criteria to minimize the exposure of participants to ionizing radiation, while 

allowing them to accomplish their missions. DOD participants at RANGER were limited to a gamma exposure 

limit of 3.0 rem∗ per 13-week period. Sampling pilots from the Air Weather Service were authorized to receive 

up to 3.9 rem because the special nature of their mission required them to penetrate the clouds resulting from 

the shots.

The Test Group was responsible for the radiological safety of all RANGER participants, and its Radiological 

Safety Section was responsible for implementing the radiological safety procedures. This section consisted of 

personnel from the AEC, the Los Alamos Scientific Laboratory (LASL), and the Army Corps of Engineers. 

Personnel from Headquarters, U.S. Air Force, implemented radiological safety procedures for Air Force 

participants. The general procedures followed by both groups were similar:

• Personnel dosimetry: issuing and developing film badges for participants and evaluating gamma 

radiation exposures recorded on film badges

• Use of protective equipment: providing clothing, respirators, and other protective equipment

 ∗ A rem is a radiation protection unit of measure that quantifies the risk of biological effects resulting from exposure to 

ionizing radiation. Ionizing radiation is any radiation (gamma, x-ray, beta, neutron, or alpha) capable of displacing 

electrons from atoms or molecules, thereby producing ions. According to the National Council on Radiation Protection 

and Measurements (NCRP, Report No. 160, Table 1.1), the general U.S. population receives about 0.62 rem per year 

from natural background radiation sources (radon, cosmic rays, and rocks) and man-made radiation sources (medical 

diagnostic x-rays and consumer products). As a basis of comparison, a standard diagnostic chest x-ray delivers a 

radiation dose of about 0.02 rem.
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• Monitoring: performing radiological surveys and controlling access to radiation areas

• Decontamination: detecting and removing contamination on personnel and equipment.

Radiation Doses at Operation RANGER

Shot FOX produced the most extensive radiation field. The initial radiation survey, conducted about one hour 

after the detonation, showed a maximum gamma intensity of 15.5 R/h at ground zero and 1.0 R/h about 

500 yards from ground zero. At 1,000 yards, the intensity was less than 0.05 R/h. For all RANGER shots, 

radiation levels were similar in all directions from ground zero because the fields were from neutron activation 

of the soil and all shots shared the same ground zero.

Dosimetry information is available for 40 percent of the approximately 400 DOD participants at RANGER. 

These data indicate that three individuals received doses greater than the 3.0 rem limit. The totals of 

reconstructed and film badge doses for RANGER participants are depicted below.

For more information, see the report “Operation RANGER 1951” (DNA 6022F), available online at 

http://www.dtra.mil/DTRA-Mission/Reference-Documents/NTPR-info/.

September 2021
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Summary of Operation RANGER Nuclear Weapons Tests (1951)a

Shot ABLE BAKER EASY BAKER-2 FOX

Sponsor LASL LASL LASL LASL LASL

Planned Date Jan 27 Jan 28 Feb 1 Feb 2 Feb 5

Actual Date Jan 27 Jan 28 Feb 1 Feb 2 Feb 6

Local Time 5:45 a.m. 5:52 a.m. 5:47 a.m. 5:49 a.m. 5:47 a.m.

NPG Location Frenchman

Flat

Frenchman

Flat

Frenchman

Flat

Frenchman

Flat

Frenchman

Flat

Type Airdrop Airdrop Airdrop Airdrop Airdrop

Height of Burst 

(Feet) 1,060 1,080 1,080 1,100 1,435

Yield

(Kilotons)b 1 8 1 8 22

a Source: United States Nuclear Tests, July 1945 through September 1992, DOE/NV-209 (Rev. 15), Dec 2000.

b One kiloton equals the approximate energy release of one thousand tons of TNT.
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