<s>
The	O
Advanced	O
Along	O
Track	O
Scanning	O
Radiometer	O
(	O
AATSR	B-Algorithm
)	O
is	O
one	O
of	O
the	O
Announcement	O
of	O
Opportunity	O
(	O
AO	O
)	O
instruments	O
on	O
board	O
the	O
European	O
Space	O
Agency	O
(	O
ESA	O
)	O
'	O
s	O
Envisat	B-Algorithm
satellite	O
.	O
</s>
<s>
AATSR	B-Algorithm
can	O
measure	O
Earth	O
's	O
surface	O
temperature	O
to	O
a	O
precision	O
of	O
,	O
for	O
climate	O
research	O
.	O
</s>
<s>
Among	O
the	O
secondary	O
objectives	O
of	O
AATSR	B-Algorithm
is	O
the	O
observation	O
of	O
environmental	O
parameters	O
such	O
as	O
aerosols	O
,	O
clouds	O
,	O
fires	O
,	O
gas	O
flares	O
,	O
water	O
content	O
,	O
biomass	O
,	O
and	O
vegetal	O
health	O
and	O
growth	O
.	O
</s>
<s>
AATSR	B-Algorithm
is	O
the	O
successor	O
of	O
ATSR-1	B-Algorithm
and	O
ATSR-2	B-Algorithm
,	O
payloads	O
of	O
ERS-1	B-Algorithm
and	O
ERS-2	O
.	O
</s>
<s>
In	O
order	O
to	O
achieve	O
this	O
accuracy	O
while	O
viewing	O
the	O
Earth	O
's	O
surface	O
through	O
the	O
atmosphere	O
,	O
AATSR	B-Algorithm
views	O
the	O
surface	O
at	O
two	O
angles	O
,	O
one	O
close	O
to	O
the	O
nadir	O
(	O
immediately	O
below	O
the	O
satellite	O
)	O
and	O
the	O
other	O
along	O
the	O
satellite	O
track	O
at	O
close	O
to	O
55°	O
from	O
the	O
nadir	O
,	O
thereby	O
providing	O
two	O
views	O
of	O
each	O
point	O
on	O
the	O
Earth	O
's	O
surface	O
,	O
each	O
with	O
a	O
different	O
effective	O
atmospheric	O
thickness	O
.	O
</s>
<s>
AATSR	B-Algorithm
also	O
embodies	O
an	O
exceptionally	O
precise	O
and	O
stable	O
on-board	O
calibration	O
system	O
,	O
comprising	O
two	O
reference	O
targets	O
specially	O
designed	O
for	O
high	O
uniformity	O
and	O
stability	O
.	O
</s>
<s>
These	O
two	O
targets	O
,	O
known	O
as	O
'	O
black	O
bodies	O
 '	O
are	O
maintained	O
at	O
temperatures	O
near	O
to	O
the	O
extremes	O
of	O
the	O
Earth	O
temperatures	O
as	O
measured	O
by	O
AATSR	B-Algorithm
and	O
they	O
are	O
both	O
viewed	O
during	O
each	O
scan	O
cycle	O
of	O
the	O
instrument	O
.	O
</s>
<s>
This	O
calibration	O
system	O
ensures	O
that	O
measurements	O
of	O
thermal	O
radiation	O
from	O
the	O
Earth	O
’s	O
surface	O
are	O
properly	O
calibrated	O
and	O
do	O
not	O
rely	O
on	O
ground-based	O
measurements	O
,	O
although	O
such	O
measurements	O
are	O
continually	O
used	O
to	O
evaluate	O
AATSR	B-Algorithm
’s	O
performance	O
.	O
</s>
<s>
AATSR	B-Algorithm
has	O
three	O
channels	O
at	O
thermal	O
infrared	O
wavelengths	O
,	O
from	O
which	O
surface	O
temperatures	O
are	O
derived	O
over	O
both	O
sea	O
and	O
land	O
surfaces	O
.	O
</s>
<s>
In	O
addition	O
,	O
AATSR	B-Algorithm
has	O
four	O
visible	O
and	O
near-infrared	O
wavelength	O
channels	O
which	O
are	O
used	O
to	O
identify	O
cloudy	O
areas	O
and	O
to	O
measure	O
solar	O
radiation	O
that	O
is	O
scattered	O
and	O
reflected	O
from	O
the	O
Earth	O
’s	O
surface	O
and	O
atmosphere	O
.	O
</s>
<s>
The	O
dual-view	O
measurements	O
provided	O
by	O
the	O
along-track	O
scanning	O
technique	O
is	O
also	O
a	O
key	O
feature	O
of	O
AATSR	B-Algorithm
when	O
used	O
for	O
atmospheric	O
or	O
vegetation	O
measurements	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
parallax	B-Device
between	O
the	O
two	O
views	O
can	O
be	O
used	O
to	O
determine	O
cloud	O
top	O
and	O
aerosol	O
plume	O
heights	O
using	O
geometric	O
means	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
important	O
aspects	O
of	O
the	O
ATSR	B-Algorithm
series	O
of	O
space	O
instruments	O
is	O
that	O
it	O
has	O
,	O
over	O
a	O
period	O
of	O
just	O
over	O
15	O
years	O
,	O
undergone	O
the	O
transition	O
from	O
experimental	O
sensor	O
on	O
the	O
ERS	O
satellites	O
,	O
developing	O
the	O
technique	O
and	O
demonstrating	O
the	O
accuracy	O
that	O
can	O
be	O
achieved	O
with	O
along-track	O
scanning	O
,	O
to	O
that	O
of	O
an	O
operational	O
system	O
,	O
within	O
Europe	O
’s	O
Envisat	B-Algorithm
and	O
future	O
GMES	B-General_Concept
Programmes	O
.	O
</s>
<s>
The	O
AATSR	B-Algorithm
is	O
a	O
nationally	O
provided	O
instrument	O
,	O
funded	O
by	O
the	O
UK	O
’s	O
Department	O
for	O
Environment	O
,	O
Food	O
and	O
Rural	O
Affairs	O
(	O
Defra	O
)	O
in	O
order	O
to	O
support	O
their	O
programme	O
of	O
climate	O
prediction	O
and	O
research	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
significant	O
Australian	O
contribution	O
to	O
the	O
AATSR	B-Algorithm
programme	O
,	O
now	O
managed	O
by	O
the	O
Commonwealth	O
Scientific	O
and	O
Industrial	O
Research	O
Organisation	O
.	O
</s>
<s>
The	O
predecessor	O
instruments	O
,	O
ATSR-1	B-Algorithm
and	O
ATSR-2	B-Algorithm
,	O
were	O
funded	O
by	O
the	O
UK	O
's	O
Science	O
and	O
Engineering	O
Research	O
Council	O
.	O
</s>
<s>
AATSR	B-Algorithm
is	O
the	O
third	O
in	O
a	O
series	O
of	O
instruments	O
started	O
by	O
ATSR-1	B-Algorithm
,	O
which	O
was	O
launched	O
in	O
1991	O
on	O
the	O
European	B-Algorithm
Remote-Sensing	I-Algorithm
Satellite	I-Algorithm
,	O
ERS-1	B-Algorithm
.	O
</s>
<s>
This	O
was	O
followed	O
by	O
ATSR-2	B-Algorithm
on	O
ERS-2	O
in	O
1995	O
and	O
by	O
AATSR	B-Algorithm
on	O
the	O
Envisat	B-Algorithm
satellite	O
in	O
2002	O
.	O
</s>
<s>
The	O
original	O
ATSR-1	B-Algorithm
instrument	O
lacked	O
the	O
three	O
shortest	O
wavelength	O
channels	O
provided	O
by	O
AATSR	B-Algorithm
,	O
whereas	O
ATSR-2	B-Algorithm
was	O
functionally	O
identical	O
.	O
</s>
<s>
Looking	O
to	O
the	O
future	O
,	O
a	O
successor	O
instrument	O
is	O
being	O
developed	O
to	O
fly	O
on	O
ESA	O
’s	O
Sentinel	B-Algorithm
3	I-Algorithm
satellite	O
,	O
which	O
is	O
part	O
of	O
the	O
space	O
segment	O
of	O
the	O
European	O
Global	B-General_Concept
Monitoring	I-General_Concept
for	I-General_Concept
Environment	I-General_Concept
and	I-General_Concept
Security	I-General_Concept
(	O
GMES	B-General_Concept
)	O
programme	O
.	O
</s>
<s>
This	O
will	O
ensure	O
the	O
continuity	O
of	O
AATSR-standard	O
SST	O
data	O
into	O
the	O
foreseeable	O
future	O
.	O
</s>
<s>
The	O
Sentinel	B-Algorithm
3	I-Algorithm
Earth	O
observational	O
satellite	O
will	O
house	O
many	O
earth	O
observational	O
instruments	O
including	O
SLSTR	O
(	O
Sea	O
and	O
Land	O
Surface	O
Temperature	O
Radiometer	O
)	O
which	O
is	O
the	O
successor	O
to	O
AATSR	B-Algorithm
.	O
</s>
