r construction, utilities,
procurement, transportation, and communications

o The TR-2 Group, responsible for air-blast and earth-shock measurements

o The TR-3 (Physics) Group, responsible for experiments concerning
measurements of ionizing radiation

o The TR-4 Group, responsible for meteorology

o The TR-5 Group, responsible for spectrographic and photographic
measurements

o The TR-6 Group, responsible for the airblast-airborne condenser
gauges

o The TR-7 (Medical) Group, responsible for the radiological safety
and general health of the Project TRINITY participants.

Each of these groups was divided into several units. Individuals were
also assigned special tasks outside their groups, such as
communications and tracking the TRINITY cloud with a searchlight (3).

1.4 MILITARY AND CIVILIAN PARTICIPANTS IN PROJECT TRINITY

From March 1944 until the beginning of 1946, several thousand people
participated in Project TRINITY. These included not only the LASL
scientists, but also scientists, technicians, and workmen employed at
MED installations throughout the United States. According to entrance
logs, film badge data, and other records, about 1,000 people either
worked at or visited the TRINITY site from 16 July 1945 through 1946
(1; 3; 8; 15; 16).

Although supervised by Major General Groves and the Army Corps of
Engineers, many Manhattan Project personnel were civilians. Military
personnel were assigned principally to support services, such as
security and logistics, although soldiers with special skills worked
with the civilians (7; 12). Most of the military personnel were part
of the Army Corps of Engineers, although Navy and other Army personnel
were also assigned to the project (4; 12).

CHAPTER 2

THE ACTIVITIES AT PROJECT TRINITY

The TRINITY nuclear device was detonated on a 100-foot tower (shown in
figure 2-1) at UTM coordinates 630266 on the Alamogordo Bombing Range,
New Mexico, at 0530 Mountain War Time, on 16 July 1945. The
detonation had a yield of 19 kilotons and left an impression 2.9
meters deep and 335 meters wide. The cloud resulting from the
detonation rose to an altitude of 35,000 feet (5). The TRINITY
detonation is shown in figure 2-2.

At shot-time, the temperature was 21.8 degrees Celsius, and the
surface air pressure was 850 millibars. Winds at shot-time were
nearly calm at the surface but attained a speed of 10 knots from the
southwest at 10,300 feet. At 34,