<s>
A	O
Doppler	B-Device
velocity	I-Device
sensor	I-Device
(	O
DVS	O
)	O
is	O
a	O
specialized	O
Doppler	B-Algorithm
radar	I-Algorithm
that	O
uses	O
the	O
Doppler	O
effect	O
to	O
measure	O
the	O
three	O
orthogonal	O
velocity	O
components	O
referenced	O
to	O
the	O
aircraft	O
.	O
</s>
<s>
To	O
measure	O
an	O
aircraft	O
three-dimensional	O
velocity	O
,	O
a	O
Doppler	B-Algorithm
radar	I-Algorithm
antenna	O
is	O
caused	O
to	O
radiate	O
a	O
minimum	O
of	O
three	O
non-coplanar	O
microwave	O
electromagnetic	O
beams	O
toward	O
the	O
earth	O
's	O
surface	O
.	O
</s>
<s>
Some	O
of	O
the	O
energy	O
is	O
backscattered	O
to	O
the	O
radar	B-Application
by	O
the	O
earth	O
surface	O
.	O
</s>
<s>
DVS	O
transmission	O
is	O
performed	O
at	O
a	O
center	O
frequency	O
of	O
13.325	O
GHz	O
in	O
the	O
internationally	O
authorized	O
Ku	B-Algorithm
band	I-Algorithm
of	O
13.25	O
to	O
13.4GHz	O
.	O
</s>
<s>
Because	O
the	O
Doppler	B-Algorithm
radar	I-Algorithm
measures	O
velocity	O
relative	O
to	O
surface	O
,	O
sea	O
current	O
and	O
tidal	O
effects	O
create	O
biases	O
.	O
</s>
<s>
These	O
radars	B-Application
were	O
formally	O
approved	O
under	O
the	O
FAA	O
TSO-65a	O
until	O
2013	O
,	O
and	O
are	O
designed	O
in	O
accordance	O
with	O
the	O
Radio	O
Technical	O
Commission	O
for	O
Aeronautics	O
(	O
RTCA	O
)	O
DO-158	O
standard	O
titled	O
Minimum	O
Performance	O
Standards	O
−	O
Airborne	O
Doppler	B-Algorithm
Radar	I-Algorithm
Navigation	O
Equipment	O
.	O
</s>
<s>
The	O
functional	O
operation	O
and	O
accuracy	O
of	O
Doppler	B-Device
velocity	I-Device
sensors	I-Device
is	O
affected	O
by	O
many	O
factors	O
,	O
including	O
aircraft	O
velocity	O
,	O
attitude	O
and	O
altitude	B-Application
above	O
terrain	O
.	O
</s>
<s>
It	O
is	O
also	O
affected	O
by	O
environmental	O
factors	O
,	O
including	O
the	O
type	O
of	O
terrain	O
the	O
radar	B-Application
is	O
illuminating	O
,	O
and	O
precipitation	O
in	O
the	O
atmosphere	O
.	O
</s>
