aiter consizeration of several system types (ratar, Cotar, and ghase com
parison dewices such as Ninitrack Mz I and Microlock), ic was determined that
the systes most lizely to meet all cesign criteria was a motification of the
Minitrack “k LI.
MIDOT (Multizle Interferometer Deter=ination of TIrejectory), the system
that was evolved, is a passive, mill-recording, angle~-measuring device.
A
radio interferometer using two crossed base lines, MIDOT operates from the
Celemetering sisual.
A typical MIDOT installation coasists of two antennas
mounted on each of two orthogonal base lines.
The base-line length chosen
Was approximately 100 wavelengths at the telemetering frequencies.
Signals frum antemmas at each end of a single base line are added together
at an RF tee Iccated midway between the antennas.
From this tee the signal {s
sent to a staniard telemetering receiver when a record of signal strength is
made.
When arrival tise of the transmitted signal is 180 degrees out of phase
at the two anteceas, a mill results at the tee.
Through application of rela-
tively simple geometric relationships it can be demonstrated that, for the oll
to occur, the transmitter must be located on a cone the apex of which is at the
center of the base line.
When double base lines are used, the transmitter loca-
tion is deternimed to be on a line formed by the intersection of two cones.
Therefore, given two or more double base-line stations, the position of the
transmitter aay be determined as the intersection of lines froma the stations.
The system is ambiguous, but the ambiguity can be resolved when the initial
condition geometry is known.
Experimental data indicate chat the system in
the field will yield data accurate to about & mils, or approximately t 1000
feet at a range of 250,000 feet with a baseline between stations of 10,000 t
1000 feet.
Figure 9.% is a block diagram of a single base-line, seven-channel recording station.
The helical antennas feed Andrews Coupany Beliax cable to
the tee at the aiddle.
From the tee the signal is fed to ASCOP milticouplers
and then to Sens-Clarke crystal-controlled receivers.
Signal strength at
each receiver is recorded by a Miller paper oscillograph.
Data reduction is
conplex and time-consuming and requires use of analog and digital computers.
Ok