<s>
AutoChem	B-Application
is	O
NASA	O
release	O
software	O
that	O
constitutes	O
an	O
automatic	O
computer	O
code	O
generator	O
and	O
documenter	O
for	O
chemically	O
reactive	O
systems	O
written	O
by	O
David	O
Lary	O
between	O
1993	O
and	O
the	O
present	O
.	O
</s>
<s>
AutoChem	B-Application
then	O
searches	O
chemical	O
reaction	O
databases	O
for	O
these	O
species	O
and	O
automatically	O
constructs	O
the	O
ordinary	O
differential	O
equations	O
(	O
ODE	O
)	O
that	O
describe	O
the	O
chemical	O
system	O
.	O
</s>
<s>
AutoChem	B-Application
symbolically	O
differentiates	B-Algorithm
the	O
time	O
derivatives	B-Algorithm
to	O
give	O
the	O
Jacobian	O
matrix	O
,	O
and	O
symbolically	O
differentiates	B-Algorithm
the	O
Jacobian	O
matrix	O
to	O
give	O
the	O
Hessian	O
matrix	O
and	O
the	O
adjoint	O
.	O
</s>
<s>
AutoChem	B-Application
documents	O
the	O
whole	O
process	O
in	O
a	O
set	O
of	O
LaTeX	B-Application
and	O
PDF	B-Application
files	I-Application
.	O
</s>
<s>
The	O
reactions	O
involving	O
the	O
user	O
specified	O
constituents	O
are	O
extracted	O
by	O
the	O
first	O
AutoChem	B-Application
preprocessor	O
program	O
called	O
Pick	O
.	O
</s>
<s>
This	O
subset	O
of	O
reactions	O
is	O
then	O
used	O
by	O
the	O
second	O
AutoChem	B-Application
preprocessor	O
program	O
RoC	O
(	O
rate	O
of	O
change	O
)	O
to	O
generate	O
the	O
time	O
derivatives	B-Algorithm
,	O
Jacobian	O
,	O
and	O
Hessian	O
.	O
</s>
<s>
A	O
huge	O
observational	O
database	O
of	O
many	O
different	O
atmospheric	O
constituents	O
from	O
a	O
host	O
of	O
platforms	O
are	O
available	O
from	O
the	O
AutoChem	B-Application
site	O
.	O
</s>
<s>
AutoChem	B-Application
has	O
been	O
used	O
to	O
perform	O
long	O
term	O
chemical	O
data	O
assimilation	O
of	O
atmospheric	O
chemistry	O
.	O
</s>
<s>
This	O
assimilation	O
was	O
automatically	O
documented	O
by	O
the	O
AutoChem	B-Application
software	O
and	O
is	O
available	O
on	O
line	O
at	O
CDACentral	O
.	O
</s>
