Evening star., 1938-03-12

Stratosphere-p e-probing brass brains,
first announced by the Bureau of Stand
ards about year ago, now have been
perfected to the point where they are
ready for routine daily use in making
weather observations.
Attached to unnamed balloons, these
robot observers make accurate records
of temperature, humidity, wind direc-
tions and other weather. determining
factors in the great ocean of thin air
IL to IS miles above the earthS surface.
They radio their observations back to
the ground as soon as they make them
During the past year, according to an
announcement by the Bureau OF Stand
ards, the radiometeorograph has been
greatly improved and subjected to rigid
tests. Fifty early-morning soundings
were made at the Naval Air Station
here. These soundings were timed to
occur practically simultaneously with
the regular early morning Navy air.
ment was reached between the signals
sent back from the robots and the rec
ords of instruments in the piloted planes.
The accuracy of the meteorograph Is
of the same order as that OF the air
plane instruments, says the Bureau OF
Standards report on these tests. IN
addition the robot can be used under
adverse weather conditions and can at
tain attitudes of Is miles, compared with
miles for the average alrplane flight
1t can make practically every observa-
ton needed in making up weather maps.
The decrease in barometric pressure as
the balloon rises is utilized to operate
small switch arm which moves over
strip of electrical insulating and con-
Quoting strips. The conducting strips
are electrically interconnected with two
resistors which control the modulatlng
frequency or pitch of the radio signals.
One of these resstors consists OF
small capillary glass tube filled with an
electrolytic which varies markedly IN
electrical resistance with the surround
ing air temperature. The second reslstor
is mechanically varied by the expansion
or contraction of hair element, ana
hence varies with the relative humldlty.
The temperature resistor is normally in
circuit so that the pitch is proportional
to the temperature.
At predetermined pressure levels cor
responding to 500-foot stages in the
height of the balloon. the switch arm
switches in the humidity resistor and
the pitch becomes measure of the rela-
tive humidity. At the ground receiving
station an automatic frequency recorder
converts the variations in pitch into
plot of humidity and temperature against
pressure. The improvements incorpo-
rated in the system during the past year
have increased the stability of the in
strument and the accuracy of signals
to the ground station. Other improve
ments enable the robots to be manu-
factured at lower cost.
The results of the comparison tests
OF the radiometeorograph and the aero
graph showed agreement of tempera-
ture readings within two per cent and
IN humidity readings within 10 per cent
relative humidity. One unusual COM
parison test is of interest. On Novem-
Der 3 new airmass passed over Ana
costa just after the release of the
radlometeorograph. The robot observer
was carried away with the old air mass,
while the airplane sounding made a
little later was in the new airmass. OBJ
servations obtained in an airplane over
Nor1olk an hour earlier showed the
same temperature inversion indicated by
the radiometeorograph and not shown
oy the Anacostia airp1Hne record. A