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ASDE Radar Equipment
Airport Surface Detection Equipment (ASDE), short -range, K -band
radar, supplements or replaces the visual observation of the
control -tower operator. This article reviews the design considerations,
construction and performance of a new system now being
developed for the Air Force.
ii-baud, had a pulse width of about
0.1 µsec; its antenna beamwidth
was 0.4 degree in azimuth and 1.0
degree in elevation. This represents
a pulse of 50 ft. in range and,
at a distance of 7000 ft., 50 ft. in
azimuth. There was considerable
interest in this radar, which displayed
the runways and taxiways
of an airport with aircraft moving
around on them.
Early observations of the capabilities
of the first Taxi Radar
proved that it did have considerable
promise as an aid in surface traffic
control. However, it became evident
that increased resolution would
be highly desirable, and Airborne
Instruments Laboratory received a
contract to modify one of the Taxi
Radar equipments to obtain increased
resolution. To do this, the
transmitter pulse length was reduced
to 0.02 µsec, and the receiver
bandwidth and indicator resolution
were improved to adequately display
this short pulse. The Air
Force decided against increasing
the antenna size on this program.
However, it was decided to add a
spoiler plate to the existing reflector
to fan out the vertical -plane
radiation pattern of the antenna.
This was done to provide better
coverage of close -in areas when
the antenna was located some distance
above the ground.
The equipment resulting from
this modification was known as the
Experimental Model of ASDE. As
the name indicates, it was an experimental
equipment and was
known to have some shortcomings
that would not be desirable in a
final model. However, the basic
performance of the system was not
affected, and the equipment was
used in an extensive evaluation
testing program.
After a short shake -down test at
Mitchell AFB, conducted by AIL,
the experimental model was taken
to the CAA Technical Development
Evaluation Center (TDEC) at Indianapolis.
There it was subjected
to a thorough technical as well as
operational evaluation. As part of
the evaluation program, the radar
was moved to the municipal airport
at Minneapolis, Minn., during the
winter of 1951 -1952 to check its op-
eration in heavy snow. It was
found, incidentally, that falling
snow did not bother the operation
of the radar, but that a snow -covered
airport looked entirely different
on the PPI display. The smooth
snow surface gave no returned signal,
but the snowbanks on the side
of a plowed runway gave a clear
outline of the runway.
Fig. 3: (r) Antenna construction.
Surface tolerance
is severe, to within 1/32 in.
Fig. 4: PPI screen provides
this picture of a 4- engine
I DC -61 aircraft at end of
runway
Upon completion of the tests by
TDEC, the Experimental Model of
ASDE was taken to Rome Air Development
Center (RADC) for a
brief testing period. While at
RADC, the equipment was made
ready for installation in the new
control tower at New York International
Airport (Idlewild).
In the spring of 1952, the Experimental
Model of ASDE was
installed in the new 11 -story control
tower at Idlewild. The antenna
and the transmitter -receiver were
located on the roof, one PPI was
located in the control cab, and one
in the approach control room along -
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