RAWINSONDE SYSTEMS Al-3 
2.2 Transponder. The transponder- radiosonde is essentially the same 
as that used in the basic system except that a ranging capability is built 
into the radiosonde. The slant range between the transponder- radiosonde 
and the tracking unit is obtained by measuring the phase difference be- 
tween the transmitted and received range signal generated in the ground- 
based transmitter. This signal is received and retransmitted by the 
radiosonde to the ground-based receiving equipment. The difference in 
phase between the transmitted and received range signal is a measure 
of slant range. The phase difference occurs because of the finite time 
required for the range signal to travel from the ground-based trans- 
mitter to the radiosonde and back again. A phase change of one complete 
cycle corresponds to a range change of 2000 meters. The cumulative 
phase shift is a measure of the total range change. Stations that use 
equipment with ranging capability compute winds using slant range and 
elevation angle or slant range and computed height to obtain distance 
from observation point. On some transponder-radiosondes, the conven- 
tional baroswitch commutator is replaced with a clock switch com- 
mutator. 
2.3 Transponder-Hypsometer, This radiosonde combines the features 
of both the transponder and hypsometer type radiosondes. 
2.4 Rabal. An optical theodolite is used to obtain the elevation and 
azimuth angles of the radiosonde for winds-aloft computations. 
2.5 Automatic Wind and Height Systems. An analog-to-digital con- 
verter and a digital computer are addedtothe basic rawinsonde system, 
The meteorological data processor provides, on punched tape, azimuth 
and elevation tracking angles, slant range, temperature and humidity 
data, and elapsed time. Prelaunch calibration data, station identification, 
etc., may be entered manually. 
2.6 Radar Wind. A target, suitably matched to the frequency of the 
radar in use, is attached to the trainof the radiosonde balloon. The radar 
will provide the slant range to the target by measurement of the time 
interval between the transmitted and reflected radar pulse. The azimuth 
indicator of the radar set will indicate the azimuth angle of the target. 
Slant range is used in conjunction with height data, computed from the 
radiosondes' meteorological data, to compute distance from observation 
point. 
2.7 Radiosonde System. A radiosonde system is basically the same as 
a rawinsonde system except that winds-aloft data are not provided. 
1-1-69 FMH#3 
