<s>
Envisat	B-Algorithm
(	O
"	O
Environmental	O
Satellite	O
"	O
)	O
is	O
a	O
large	O
inactive	O
Earth-observing	O
satellite	O
which	O
is	O
still	O
in	O
orbit	B-Application
and	O
now	O
considered	O
space	O
debris	O
.	O
</s>
<s>
It	O
was	O
launched	O
on	O
1	O
March	O
2002	O
aboard	O
an	O
Ariane	O
5	O
from	O
the	O
Guyana	O
Space	O
Centre	O
in	O
Kourou	O
,	O
French	O
Guiana	O
,	O
into	O
a	O
Sun	O
synchronous	O
polar	O
orbit	B-Application
at	O
an	O
altitude	O
of	O
790±10km	O
.	O
</s>
<s>
It	O
orbits	B-Application
the	O
Earth	O
in	O
about	O
101	O
minutes	O
,	O
with	O
a	O
repeat	O
cycle	O
of	O
35	O
days	O
.	O
</s>
<s>
After	O
losing	O
contact	O
with	O
the	O
satellite	O
on	O
8	O
April	O
2012	O
,	O
ESA	O
formally	O
announced	O
the	O
end	O
of	O
Envisat	B-Algorithm
's	O
mission	O
on	O
9	O
May	O
2012	O
.	O
</s>
<s>
Envisat	B-Algorithm
cost	O
2.3	O
billion	O
Euro	O
(	O
including	O
300	O
million	O
Euro	O
for	O
5	O
years	O
of	O
operations	O
)	O
to	O
develop	O
and	O
launch	O
.	O
</s>
<s>
The	O
first	O
of	O
these	O
,	O
Sentinel	B-Algorithm
1	I-Algorithm
,	O
has	O
taken	O
over	O
the	O
radar	B-Application
duties	O
of	O
Envisat	B-Algorithm
since	O
its	O
launch	O
in	O
2014	O
.	O
</s>
<s>
Envisat	B-Algorithm
was	O
launched	O
as	O
an	O
Earth	O
observation	O
satellite	O
.	O
</s>
<s>
Its	O
objective	O
was	O
to	O
service	O
the	O
continuity	O
of	O
European	B-Algorithm
Remote-Sensing	I-Algorithm
Satellite	I-Algorithm
missions	O
,	O
providing	O
additional	O
observational	O
parameters	O
to	O
improve	O
environmental	O
studies	O
.	O
</s>
<s>
In	O
working	O
towards	O
the	O
global	O
and	O
regional	O
objectives	O
of	O
the	O
mission	O
,	O
numerous	O
scientific	O
disciplines	O
currently	O
use	O
the	O
data	O
acquired	O
from	O
the	O
different	O
sensors	O
on	O
the	O
satellite	O
to	O
study	O
such	O
things	O
as	O
atmospheric	O
chemistry	O
,	O
ozone	O
depletion	O
,	O
biological	O
oceanography	O
,	O
ocean	O
temperature	O
and	O
colour	O
,	O
wind	O
waves	O
,	O
hydrology	O
(	O
humidity	O
,	O
floods	O
)	O
,	O
agriculture	O
and	O
arboriculture	O
,	O
natural	O
hazards	O
,	O
digital	B-Application
elevation	I-Application
modelling	I-Application
(	O
using	O
interferometry	O
)	O
,	O
monitoring	O
of	O
maritime	O
traffic	O
,	O
atmospheric	O
dispersion	O
modelling	O
(	O
pollution	O
)	O
,	O
cartography	O
and	O
study	O
of	O
snow	O
and	O
ice	O
.	O
</s>
<s>
×	O
×	O
in	O
orbit	B-Application
with	O
the	O
solar	O
array	O
deployed	O
.	O
</s>
<s>
Envisat	B-Algorithm
carries	O
an	O
array	O
of	O
nine	O
Earth-observation	O
instruments	O
that	O
gathered	O
information	O
about	O
the	O
Earth	O
(	O
land	O
,	O
water	O
,	O
ice	O
,	O
and	O
atmosphere	O
)	O
using	O
a	O
variety	O
of	O
measurement	O
principles	O
.	O
</s>
<s>
Several	O
of	O
the	O
instruments	O
were	O
advanced	O
versions	O
of	O
instruments	O
that	O
were	O
flown	O
on	O
the	O
earlier	O
ERS-1	B-Algorithm
and	O
ERS	B-Algorithm
2	I-Algorithm
missions	O
and	O
other	O
satellites	O
.	O
</s>
<s>
AATSR	B-Algorithm
(	O
Advanced	O
Along	O
Track	O
Scanning	O
Radiometer	O
)	O
can	O
measure	O
the	O
sea	O
surface	O
temperature	O
in	O
the	O
visible	O
and	O
infrared	O
spectra	O
.	O
</s>
<s>
It	O
is	O
the	O
successor	O
of	O
ATSR1	O
and	O
ATSR2	O
,	O
payloads	O
of	O
ERS	B-Algorithm
1	I-Algorithm
and	O
ERS	B-Algorithm
2	I-Algorithm
.	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
water	O
content	O
,	O
biomass	O
,	O
and	O
vegetal	O
health	O
and	O
growth	O
.	O
</s>
<s>
MIPAS	B-Algorithm
(	O
Michelson	O
Interferometer	O
for	O
Passive	O
Atmospheric	O
Sounding	O
)	O
is	O
a	O
Fourier	O
transforming	O
infrared	O
spectrometer	O
which	O
provides	O
pressure	O
and	O
temperature	O
profiles	O
,	O
and	O
profiles	O
of	O
trace	O
gases	O
nitrogen	O
dioxide	O
(	O
)	O
,	O
nitrous	O
oxide	O
(	O
)	O
,	O
methane	O
(	O
)	O
,	O
nitric	O
acid	O
(	O
)	O
,	O
ozone	O
(	O
)	O
,	O
and	O
water	O
(	O
)	O
in	O
the	O
stratosphere	O
.	O
</s>
<s>
MIPAS	B-Algorithm
has	O
a	O
vertical	O
resolution	O
of	O
depending	O
on	O
altitude	O
(	O
the	O
larger	O
at	O
the	O
level	O
of	O
the	O
upper	O
stratosphere	O
)	O
.	O
</s>
<s>
SCIAMACHY	B-Algorithm
(	O
SCanning	O
Imaging	O
Absorption	O
spectroMeter	O
for	O
Atmospheric	O
CHartographY	O
)	O
compares	O
light	O
coming	O
from	O
the	O
sun	O
to	O
light	O
reflected	O
by	O
the	O
Earth	O
,	O
which	O
provides	O
information	O
on	O
the	O
atmosphere	O
through	O
which	O
the	O
Earth-reflected	O
light	O
has	O
passed	O
.	O
</s>
<s>
SCIAMACHY	B-Algorithm
is	O
an	O
image	O
spectrometer	O
with	O
the	O
principal	O
objective	O
of	O
mapping	O
the	O
concentration	O
of	O
trace	O
gases	O
and	O
aerosols	O
in	O
the	O
troposphere	O
and	O
stratosphere	O
.	O
</s>
<s>
SCIAMACHY	B-Algorithm
uses	O
3	O
different	O
targeting	O
modes	O
:	O
to	O
the	O
nadir	O
(	O
against	O
the	O
sun	O
)	O
,	O
to	O
the	O
limbus	O
(	O
through	O
the	O
atmospheric	O
corona	O
)	O
,	O
and	O
during	O
solar	O
or	O
lunar	O
eclipses	O
.	O
</s>
<s>
SCIAMACHY	B-Algorithm
was	O
built	O
by	O
Netherlands	O
and	O
Germany	O
at	O
TNO/TPD	O
,	O
SRON	O
and	O
Airbus	O
Defence	O
and	O
Space	O
Netherlands	O
.	O
</s>
<s>
RA-2	O
(	O
Radar	B-Application
Altimeter	O
2	O
)	O
is	O
a	O
dual-frequency	O
Nadir	O
pointing	O
Radar	B-Application
operating	O
in	O
the	O
Ku	B-Algorithm
band	I-Algorithm
and	O
S	B-Algorithm
bands	I-Algorithm
,	O
it	O
is	O
used	O
to	O
define	O
ocean	O
topography	O
,	O
map/monitor	O
sea	O
ice	O
and	O
measure	O
land	O
heights	O
.	O
</s>
<s>
Mean	O
sea	O
level	O
measurements	O
from	O
Envisat	B-Algorithm
are	O
continuously	O
graphed	O
at	O
the	O
web	O
site	O
,	O
on	O
the	O
.	O
</s>
<s>
ASAR	O
(	O
Advanced	O
Synthetic	O
Aperture	O
Radar	B-Application
)	O
operates	O
in	O
the	O
C	B-Algorithm
band	I-Algorithm
in	O
a	O
wide	O
variety	O
of	O
modes	O
.	O
</s>
<s>
It	O
served	O
as	O
a	O
data	O
link	O
for	O
ERS	B-Algorithm
1	I-Algorithm
and	O
ERS	B-Algorithm
2	I-Algorithm
,	O
providing	O
numerous	O
functions	O
such	O
as	O
observations	O
of	O
different	O
polarities	O
of	O
light	O
or	O
combining	O
different	O
polarities	O
,	O
angles	O
of	O
incidence	O
and	O
spatial	O
resolutions	O
.	O
</s>
<s>
DORIS	O
(	O
Doppler	O
Orbitography	O
and	O
Radiopositioning	O
Integrated	O
by	O
Satellite	O
)	O
determines	O
the	O
satellite	O
's	O
orbit	B-Application
to	O
within	O
.	O
</s>
<s>
ESA	O
announced	O
on	O
12	O
April	O
2012	O
that	O
they	O
lost	O
contact	O
with	O
Envisat	B-Algorithm
on	O
Sunday	O
,	O
8	O
April	O
2012	O
,	O
after	O
10	O
years	O
of	O
service	O
,	O
exceeding	O
the	O
initially	O
planned	O
life	O
span	O
by	O
5	O
years	O
.	O
</s>
<s>
The	O
spacecraft	O
was	O
still	O
in	O
a	O
stable	O
orbit	B-Application
,	O
but	O
attempts	O
to	O
contact	O
it	O
were	O
unsuccessful	O
.	O
</s>
<s>
Ground-based	O
radar	B-Application
and	O
the	O
French	O
Pleiades	O
Earth	O
probe	O
were	O
used	O
to	O
image	O
the	O
silent	O
Envisat	B-Algorithm
and	O
look	O
for	O
damage	O
.	O
</s>
<s>
ESA	O
formally	O
announced	O
the	O
end	O
of	O
Envisat	B-Algorithm
's	O
mission	O
on	O
9	O
May	O
2012	O
.	O
</s>
<s>
Envisat	B-Algorithm
was	O
launched	O
in	O
2002	O
and	O
it	O
operated	O
five	O
years	O
beyond	O
its	O
planned	O
mission	O
lifetime	O
,	O
delivering	O
over	O
a	O
petabyte	O
of	O
data	O
.	O
</s>
<s>
Envisat	B-Algorithm
poses	O
a	O
hazard	O
because	O
of	O
the	O
risk	O
of	O
collisions	O
with	O
space	O
debris	O
.	O
</s>
<s>
Given	O
its	O
orbit	B-Application
and	O
its	O
area-to-mass	O
ratio	O
,	O
it	O
will	O
take	O
about	O
150	O
years	O
for	O
the	O
satellite	O
to	O
be	O
gradually	O
pulled	O
into	O
the	O
Earth	O
's	O
atmosphere	O
.	O
</s>
<s>
Envisat	B-Algorithm
is	O
currently	O
orbiting	O
in	O
an	O
environment	O
where	O
two	O
catalogued	O
space	O
debris	O
objects	O
can	O
be	O
expected	O
to	O
pass	O
within	O
about	O
of	O
it	O
every	O
year	O
,	O
which	O
would	O
likely	O
trigger	O
the	O
need	O
for	O
a	O
manoeuvre	O
to	O
avoid	O
a	O
possible	O
collision	O
.	O
</s>
<s>
A	O
collision	O
between	O
a	O
satellite	O
the	O
size	O
of	O
Envisat	B-Algorithm
and	O
an	O
object	O
as	O
small	O
as	O
10kg	O
could	O
produce	O
a	O
very	O
large	O
cloud	O
of	O
debris	O
,	O
initiating	O
a	O
self-sustaining	O
chain-reaction	O
of	O
collisions	O
and	O
fragmentation	O
with	O
production	O
of	O
new	O
debris	O
,	O
a	O
phenomenon	O
known	O
as	O
the	O
Kessler	O
Syndrome	O
.	O
</s>
<s>
Envisat	B-Algorithm
was	O
a	O
candidate	O
for	O
a	O
mission	O
to	O
remove	O
it	O
from	O
orbit	B-Application
,	O
called	O
e.Deorbit	O
.	O
</s>
<s>
The	O
spacecraft	O
sent	O
to	O
bring	O
down	O
Envisat	B-Algorithm
would	O
itself	O
need	O
to	O
have	O
a	O
mass	O
of	O
approximately	O
1.6	O
tonnes	O
.	O
</s>
