d zero and thus remained unmanned.
At the south shelter, the Medical Group set up a "going-in" station
where personnel were required to stop to put on protective clothing
(coveralls, booties, caps, and cotton gloves) and pick up monitoring
equipment before entering the ground zero area. Since it was not
known how much radioactive material might be suspended in the air, all
personnel entering the ground zero area wore complete protective
covering and respirators for the first three days after the
detonation. Figure 2-6 shows two Project TRINITY personnel wearing
protective clothing (1).

On the day of the shot, five parties entered the ground zero area.
One party consisted of eight members of the earth-sampling group.
They obtained samples by driving to within 460 meters of ground zero
in a tank specially fitted with rockets to which retrievable
collectors were fastened in order to gather soil samples from a
distance. This group made several sampling excursions on 16 and 17
July. The tank carried two personnel (a driver and a passenger) each
trip. No member of this party received a radiation exposure of more
than 1 roentgen (1).

Five other men from the earth-sampling group entered the ground zero
area in a second tank, lined with lead for radiation protection. The
tank, carrying the driver and one passenger, made five trips into the
ground zero area to retrieve soil samples on 16 and 17 July. On two
trips, the tank passed over ground zero; on the others, it approached
to within about 90 meters of ground zero. The men scooped up soil
samples through a trap door in the bottom of the tank. One driver who
made three trips into the ground zero area received the highest
exposure, 15 roentgens (1).

This lead-lined tank was also used by ten men to observe the radiation
area. These men, traveling two at a time, made five trips into the
area on shot-day but never approached closer than 1,370 meters to
ground zero. The highest exposure among these ten men was 0.3
roentgens (1).

The next party to approach ground zero consisted of a photographer and
a radiological safety monitor. Wearing protective clothing and
respirators, the two men were about 730 meters northwest of ground
zero photographing "JUMBO" from 1100 to 1200 hours. "JUMBO," shown in
figure 2-7, was a massive container built to contain the
high-explosive detonation of the TRINITY device and to allow recovery
of the fissionable material if the device