<s>
The	O
ODOP	B-Algorithm
(	O
Offset	O
DOPpler	B-Algorithm
)	O
radar	O
tracking	O
system	O
is	O
essentially	O
the	O
same	O
as	O
the	O
UDOP	B-Algorithm
system	O
used	O
for	O
many	O
years	O
at	O
the	O
Atlantic	O
Missile	O
Range	O
,	O
but	O
ODOP	B-Algorithm
operates	O
at	O
different	O
frequencies	O
.	O
</s>
<s>
It	O
is	O
a	O
phase-coherent	O
,	O
multistation	O
Doppler	B-Algorithm
tracking	O
system	O
which	O
measures	O
position	O
of	O
a	O
vehicle	O
equipped	O
with	O
the	O
ODOP	B-Algorithm
transponder	O
.	O
</s>
<s>
ODOP	B-Algorithm
stations	O
are	O
located	O
at	O
and	O
around	O
Cape	O
Kennedy	O
.	O
</s>
<s>
The	O
ODOP	B-Algorithm
transponder	O
is	O
carried	O
in	O
the	O
first	O
stage	O
(	O
S-IB	O
or	O
S-IC	O
)	O
of	O
the	O
Saturn	O
vehicles	O
and	O
,	O
therefore	O
,	O
ODOP	B-Algorithm
tracking	O
data	O
is	O
limited	O
to	O
the	O
flight	O
of	O
the	O
first	O
stage	O
only	O
.	O
</s>
<s>
The	O
ODOP	B-Algorithm
tracking	O
system	O
provides	O
data	O
immediately	O
following	O
lift-off	O
while	O
other	O
tracking	O
systems	O
cannot	O
"	O
see	O
"	O
the	O
vehicle	O
or	O
their	O
accuracy	O
is	O
reduced	O
by	O
multipath	O
propagation	O
during	O
the	O
early	O
phase	O
of	O
the	O
flight	O
.	O
</s>
<s>
The	O
ODOP	B-Algorithm
system	O
is	O
a	O
radar	O
interferometer	O
tracking	O
system	O
which	O
determines	O
the	O
position	O
of	O
a	O
vehicle-borne	O
transponder	O
.	O
</s>
<s>
The	O
signal	O
from	O
the	O
transponder	O
received	O
at	O
the	O
ground	O
stations	O
contains	O
a	O
2-way	O
Doppler	B-Algorithm
shift	O
fD	O
which	O
is	O
extracted	O
by	O
mixing	O
the	O
received	O
signal	O
(	O
fi	O
=	O
960MHz	O
+	O
fD	O
)	O
with	O
the	O
reference	O
frequency	O
(	O
fR	O
=	O
960MHz	O
)	O
derived	O
from	O
the	O
transmitter	O
frequency	O
.	O
</s>
<s>
Actually	O
,	O
a	O
reference	O
frequency	O
of	O
53.33MHz	O
is	O
transmitted	O
over	O
a	O
VHF	B-Algorithm
link	O
to	O
each	O
transmitter	O
station	O
and	O
then	O
multiplied	O
by	O
a	O
factor	O
of	O
18	O
,	O
yielding	O
959.94MHz	O
.	O
</s>
<s>
When	O
this	O
frequency	O
is	O
combined	O
with	O
the	O
signal	O
received	O
from	O
the	O
transponder	O
,	O
the	O
Doppler	B-Algorithm
shift	O
is	O
obtained	O
with	O
a	O
60kHz	O
bias	O
frequency	O
(	O
60kHz	O
+	O
fD	O
)	O
.	O
</s>
<s>
The	O
UDOP	B-Algorithm
system	O
used	O
a	O
transmitter	O
frequency	O
of	O
450MHz	O
which	O
was	O
doubled	O
in	O
the	O
transponder	O
(	O
900MHz	O
)	O
.	O
</s>
<s>
The	O
higher	O
frequency	O
in	O
the	O
ODOP	B-Algorithm
system	O
(	O
890MHz	O
versus	O
450MHz	O
)	O
is	O
less	O
affected	O
by	O
the	O
ionosphere	O
and	O
the	O
result	O
is	O
increased	O
tracking	O
accuracy	O
.	O
</s>
<s>
The	O
Doppler	B-Algorithm
frequencies	O
,	O
fD	O
,	O
(	O
including	O
the	O
bias	O
frequency	O
)	O
from	O
all	O
receiving	O
stations	O
are	O
transmitted	O
to	O
the	O
central	O
station	O
and	O
recorded	O
on	O
magnetic	O
tape	O
.	O
</s>
<s>
Integration	O
of	O
the	O
Doppler	B-Algorithm
frequency	O
received	O
at	O
a	O
particular	O
station	O
provides	O
the	O
range	O
sum	O
,	O
i.e.	O
,	O
the	O
distance	O
transmitter-transponder	O
receiver	O
.	O
</s>
<s>
The	O
ODOP	B-Algorithm
system	O
uses	O
20	O
receiver	O
stations	O
around	O
Cape	O
Kennedy	O
for	O
redundancy	O
and	O
optimum	O
tracking	O
geometry	O
.	O
</s>
<s>
ODOP	B-Algorithm
tracking	O
data	O
is	O
not	O
available	O
in	O
real	O
time	O
but	O
is	O
obtained	O
from	O
post-flight	O
evaluation	O
.	O
</s>
<s>
The	O
ODOP	B-Algorithm
transponder	O
is	O
a	O
modified	O
version	O
of	O
the	O
transponder	O
used	O
by	O
the	O
Jet	O
Propulsion	O
Laboratory	O
in	O
the	O
Ranger	O
vehicles	O
.	O
</s>
