Figure 2-2.MX-8577/SSQ-61 bathythermograph through-the-hull launcher.
bathythermograph probe (fig. 2-3), equipment
components are all interchangeable. The standard
probe is manufactured by the Sippican Corporation and
is widely known as the T-4 probe, rather than as the OC-
An expendable bathythermograph probe is
popularly called an XBT. An XBT consists of a probe
with a thermistor installed in the nose and a canister.
The probe descends at a known rate through the water,
and the recorder converts the thermistors electrical
resistance (and descent time) into depth and
temperature units. The thermistor is connected by a fine
wire to contact pins mounted in the end of the canister,
which is retained in the launcher during the
measurement. When the measurement is completed,
the wire breaks as the probe descends beyond the
maximum depth of the probe. The canister is then
removed from the launcher and discarded. A cable from
the launcher connects to the recorder. Specific
operation and maintenance instructions for each system
are contained in the manualscited in the reference list.
All recorders except the original RO-326 have
changeable chart drive gears and an internal selector
switch that allows operation with different types of
probes. All systems most commonly use the T-4 probe.
An XBT observation may be conducted by one
person, but it is much easier using two people with
sound-powered telephones. One person should be
stationed at the recorder (identified as A) and the
second person at the launcher (identified as "B"). With
two people (A and B), the following sequence must be
" A " :
" B " :
" B " :
" A " :
Turns on power at the recorder.
Opens launcher ball valve and breech
Removes end cap from XBT, loads
probe canister, and locks the breech.
Verifies automatic start sequence of
recorder and chart alignment.