<s>
Beam	B-Algorithm
park	I-Algorithm
is	O
a	O
radar	B-Application
mode	O
used	O
for	O
space	O
surveillance	O
,	O
particularly	O
tracking	O
space	O
debris	O
.	O
</s>
<s>
In	O
beam-park	O
mode	O
,	O
a	O
radar	B-Application
beam	O
is	O
kept	O
in	O
a	O
fixed	O
direction	O
with	O
respect	O
to	O
the	O
Earth	O
,	O
while	O
objects	O
passing	O
through	O
the	O
beam	O
are	O
tracked	O
.	O
</s>
<s>
In	O
24	O
hours	O
,	O
as	O
a	O
result	O
of	O
the	O
Earth	O
’s	O
rotation	O
,	O
the	O
radar	B-Application
effectively	O
scans	O
a	O
narrow	O
strip	O
through	O
360°	O
of	O
the	O
celestial	O
sphere	O
.	O
</s>
<s>
The	O
scattered	O
waves	O
are	O
detected	O
by	O
a	O
receiver	O
and	O
the	O
measurements	O
obtained	O
during	O
the	O
observations	O
can	O
be	O
used	O
to	O
determine	O
object	O
radar	B-Application
cross-section	O
,	O
time	O
of	O
peak	O
occurrence	O
,	O
polarization	O
ratio	O
,	O
doppler	O
shift	O
and	O
object	O
rotation	O
.	O
</s>
<s>
This	O
limits	O
the	O
use	O
of	O
radar-based	O
beam	B-Algorithm
park	I-Algorithm
observations	O
to	O
objects	O
in	O
Low-Earth	O
Orbit	O
(	O
LEO	O
)	O
.	O
</s>
<s>
The	O
radar	B-Application
technique	O
typically	O
outperforms	O
optical	O
facilities	O
in	O
LEO	O
and	O
can	O
conduct	O
observations	O
for	O
longer	O
periods	O
,	O
both	O
during	O
day	O
and	O
night	O
,	O
independently	O
of	O
the	O
weather	O
and	O
object	O
illumination	O
by	O
sunlight	O
.	O
</s>
<s>
The	O
tracking	O
sensitivity	O
of	O
radar-based	O
space	O
debris	O
tracking	O
systems	O
can	O
be	O
further	O
improved	O
if	O
they	O
are	O
working	O
in	O
conjunction	O
with	O
another	O
transmitter	O
or	O
receiver	O
,	O
forming	O
a	O
bistatic	B-Algorithm
radar	I-Algorithm
system	O
.	O
</s>
<s>
Several	O
US	O
radars	B-Application
were	O
the	O
first	O
to	O
start	O
carrying	O
out	O
beam-park	O
tracking	O
.	O
</s>
<s>
These	O
were	O
the	O
Haystack	O
Radar	B-Application
in	O
Massachusetts	O
,	O
Goldstone	O
Radar	B-Application
in	O
California	O
,	O
and	O
multiple	O
radars	B-Application
at	O
the	O
Kwajalein	O
Atoll	O
.	O
</s>
<s>
Most	O
notable	O
,	O
the	O
Haystack	O
radar	B-Application
is	O
capable	O
of	O
tracking	O
objects	O
as	O
small	O
as	O
2mm	O
.	O
</s>
<s>
Performing	O
observations	O
in	O
the	O
L-band	B-Algorithm
during	O
a	O
10-hour	O
long	O
experiment	O
,	O
the	O
system	O
was	O
able	O
to	O
detect	O
small-sized	O
objects	O
in	O
LEO	O
.	O
</s>
<s>
The	O
first	O
24-hour	O
operational	O
measurement	O
campaign	O
was	O
performed	O
on	O
13	O
–	O
14	O
December	O
1994	O
,	O
with	O
TIRA	O
and	O
the	O
Fylingdales	O
Phased-Array	O
Radar	B-Application
.	O
</s>
<s>
Dedicated	O
space	O
surveillance	O
sensors	O
,	O
often	O
operating	O
in	O
beam-park	O
mode	O
,	O
include	O
the	O
French	O
GRAVES	O
bistatic	B-Algorithm
radar	I-Algorithm
,	O
the	O
defunct	O
US	O
Air	O
Force	O
Space	O
Surveillance	O
System	O
(	O
Space	O
Fence	O
)	O
and	O
its	O
replacement	O
Space	O
Fence	O
.	O
</s>
<s>
Other	O
systems	O
currently	O
used	O
for	O
space	O
surveillance	O
that	O
operate	O
in	O
beam-park	O
mode	O
include	O
the	O
multistatic	B-Algorithm
EISCAT	O
incoherent	O
scatter	O
radar	B-Application
system	I-Application
and	O
the	O
Medicina	O
Radio	O
Observatory	O
's	O
Northern	O
Cross	O
Radio	O
Telescope	O
and	O
32	O
m	O
parabolic	O
dish	O
antenna	O
.	O
</s>
