<s>
The	O
AN/APS	B-Device
-20	I-Device
was	O
an	O
airborne	O
early	O
warning	O
,	O
anti-submarine	O
,	O
maritime	O
surveillance	O
and	O
weather	B-Application
radar	I-Application
developed	O
in	O
the	O
United	O
States	O
in	O
the	O
1940s	O
.	O
</s>
<s>
Shipborne	O
radar	O
did	O
not	O
have	O
sufficient	O
range	O
to	O
identify	O
attacking	O
bombers	B-Application
in	O
time	O
to	O
launch	O
defensive	O
interceptor	O
aircraft	O
due	O
to	O
the	O
radar	B-Algorithm
horizon	I-Algorithm
.	O
</s>
<s>
The	O
outcome	O
of	O
the	O
development	O
was	O
an	O
S-Band	B-Algorithm
radar	O
designated	O
AN/APS	B-Device
-20	I-Device
.	O
</s>
<s>
Cadillac	O
I	O
,	O
the	O
initial	O
platform	O
,	O
was	O
to	O
be	O
carrier-based	O
and	O
the	O
first	O
radar	O
was	O
to	O
be	O
fitted	O
to	O
converted	O
General	O
Motors	O
TBM-3	O
Avenger	O
torpedo	O
bombers	B-Application
.	O
</s>
<s>
Under	O
the	O
guise	O
of	O
Cadillac	O
II	O
,	O
it	O
was	O
decided	O
that	O
the	O
Boeing	O
B-17G	O
Flying	O
Fortress	O
heavy	O
bomber	B-Application
was	O
to	O
be	O
fitted	O
with	O
the	O
radar	O
.	O
</s>
<s>
The	O
first	O
version	O
,	O
the	O
AN/APS	O
-20A	O
,	O
had	O
,	O
initially	O
,	O
an	O
antenna	O
and	O
operated	O
on	O
a	O
frequency	O
of	O
2850	O
MHz	O
in	O
the	B-Algorithm
S	I-Algorithm
band	I-Algorithm
.	O
</s>
<s>
Initially	O
deployed	O
in	O
1953	O
,	O
the	O
E	O
model	O
operated	O
in	O
the	O
L	B-Algorithm
band	I-Algorithm
,	O
S	B-Algorithm
band	I-Algorithm
and	O
X	B-Algorithm
band	I-Algorithm
,	O
with	O
a	O
wide	O
selection	O
of	O
PRFs	O
and	O
pulse	O
widths	O
in	O
each	O
band	O
.	O
</s>
<s>
The	O
first	O
aircraft	O
equipped	O
with	O
the	O
AN/APS	B-Device
-20	I-Device
was	O
a	O
converted	O
TBM-3	O
Avenger	O
,	O
designated	O
XTBM-3W	O
,	O
which	O
first	O
flew	O
on	O
5	O
August	O
1944	O
.	O
</s>
<s>
They	O
were	O
especially	O
designed	O
to	O
combat	O
the	O
increasing	O
threat	O
of	O
Japanese	O
Kamikaze	B-Application
attacks	O
.	O
</s>
<s>
The	O
AN/APS	B-Device
-20	I-Device
was	O
installed	O
in	O
the	O
Douglas	O
AD-3W	O
Skyraider	O
,	O
which	O
replaced	O
the	O
Avenger	O
,	O
and	O
the	O
Lockheed	O
PO-2W	O
Warning	O
Star	O
,	O
a	O
specialised	O
platform	O
developed	O
from	O
the	O
Lockheed	O
L-1049	O
Super	O
Constellation	O
airliner	O
.	O
</s>
<s>
One	O
arena	O
where	O
the	O
radar	O
broke	O
new	O
ground	O
was	O
in	O
weather	B-Application
research	I-Application
,	O
particularly	O
with	O
the	O
hurricane	O
hunters	O
that	O
flew	O
into	O
tropical	O
cyclones	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
VW-1	O
was	O
providing	O
a	O
similar	O
service	O
tracking	O
typhoons	B-General_Concept
in	O
the	O
Pacific	O
.	O
</s>
<s>
Meanwhile	O
,	O
in	O
1948	O
,	O
the	O
UK	O
evaluated	O
a	O
PB-1W	O
equipped	O
with	O
AN/APS	B-Device
-20	I-Device
against	O
a	O
Vickers	O
Warwick	O
V	O
fitted	O
with	O
ASV.13	O
to	O
see	O
if	O
the	O
radar	O
could	O
also	O
be	O
used	O
to	O
identify	O
surface	O
ships	O
,	O
but	O
the	O
peak	O
power	O
was	O
deemed	O
too	O
high	O
and	O
the	O
pulse	O
length	O
too	O
long	O
for	O
the	O
application	O
.	O
</s>
<s>
The	O
AN/APS	B-Device
-20	I-Device
was	O
also	O
briefly	O
used	O
as	O
part	O
of	O
the	O
Space	B-Application
Race	I-Application
,	O
supporting	O
Project	O
Mercury	O
,	O
where	O
the	O
radar	O
's	O
long	O
range	O
enabled	O
it	O
to	O
be	O
used	O
in	O
tracking	O
and	O
other	O
tasks	O
.	O
</s>
<s>
The	O
AN/APS	B-Algorithm
-80	I-Algorithm
,	O
which	O
offered	O
similar	O
capabilities	O
to	O
the	O
AN/APS	B-Device
-20	I-Device
but	O
added	O
continuous	O
360°	O
area	O
search	O
coverage	O
,	O
replaced	O
the	O
radar	O
in	O
the	O
anti-submarine	O
role	O
from	O
1961	O
.	O
</s>
<s>
The	O
Canadians	O
finally	O
replaced	O
their	O
AN/APS	B-Device
-20	I-Device
with	O
AN/APS	B-Algorithm
-115	I-Algorithm
in	O
1981	O
.	O
</s>
<s>
When	O
the	O
Royal	O
Navy	O
retired	O
their	O
last	O
AN/APS	B-Device
-20	I-Device
,	O
they	O
were	O
refurbished	O
and	O
fitted	O
to	O
retiring	O
Avro	O
Shackleton	O
MR.2	O
maritime	O
patrol	O
aircraft	O
.	O
</s>
<s>
Initial	O
version	O
developed	O
for	O
carrier-based	O
aircraft	O
with	O
single	O
CRT	B-Device
display	I-Device
.	O
</s>
