<s>
The	O
Naval	O
Observatory	O
Vector	O
Astrometry	O
Software	O
(	O
NOVAS	B-Application
)	O
is	O
a	O
software	B-Library
library	I-Library
for	O
astrometry-related	O
numerical	B-General_Concept
computations	I-General_Concept
.	O
</s>
<s>
Currently	O
,	O
NOVAS	B-Application
has	O
three	O
different	O
editions	O
,	O
for	O
C	B-Language
,	O
Fortran	B-Application
,	O
and	O
Python	B-Language
.	O
</s>
<s>
The	O
algorithms	O
used	O
by	O
NOVAS	B-Application
are	O
based	O
on	O
vector	O
astrometry	O
theories	O
and	O
the	O
IAU	O
resolutions	O
.	O
</s>
<s>
Instead	O
of	O
using	O
trigonometric	O
formulae	O
from	O
spherical	O
astrometry	O
,	O
NOVAS	B-Application
uses	O
the	O
matrix	B-Architecture
and	O
vector	O
formulation	O
which	O
is	O
more	O
rigorous	O
.	O
</s>
<s>
According	O
to	O
the	O
Astronomical	O
Applications	O
Department	O
,	O
the	O
algorithms	O
used	O
in	O
NOVAS	B-Application
are	O
identical	O
to	O
those	O
used	O
in	O
the	O
production	O
of	O
the	O
US	O
part	O
of	O
the	O
Astronomical	O
Almanac	O
.	O
</s>
<s>
The	O
NOVAS	B-Application
library	O
provides	O
three	O
levels	O
of	O
subroutines	O
(	O
functions	O
)	O
:	O
basic	O
,	O
utility	O
,	O
and	O
supervisory	O
.	O
</s>
<s>
Utility-level	O
subroutines	O
perform	O
transformations	B-Algorithm
,	O
such	O
as	O
those	O
caused	O
by	O
precession	O
,	O
nutation	O
and	O
aberration	O
.	O
</s>
<s>
The	O
NOVAS	B-Application
library	O
can	O
be	O
linked	B-Application
by	O
programs	O
that	O
work	O
with	O
positions	O
of	O
celestial	O
bodies	O
.	O
</s>
<s>
For	O
example	O
,	O
"	O
Pocket	O
Stars	O
"	O
,	O
an	O
astronomy	O
software	O
for	O
Smartphone	B-Application
and	O
PDA	B-Application
platforms	O
,	O
used	O
the	O
NOVAS	B-Application
as	O
its	O
astrometry	O
engine	O
.	O
</s>
<s>
The	O
Python	B-Language
edition	O
allows	O
calling	O
the	O
NOVAS	B-Application
functions	O
from	O
Python	B-Language
.	O
</s>
<s>
It	O
is	O
mostly	O
feature	O
complete	O
with	O
respect	O
to	O
the	O
C	B-Language
edition	O
,	O
with	O
a	O
few	O
exceptions	O
,	O
and	O
shares	O
the	O
C	B-Language
edition	O
's	O
API	O
.	O
</s>
<s>
The	O
current	O
edition	O
uses	O
Python	B-Language
's	O
foreign	O
function	B-Library
library	I-Library
,	O
ctypes	O
.	O
</s>
<s>
Future	O
versions	O
of	O
the	O
Python	B-Language
interface	O
will	O
add	O
support	O
for	O
passing	O
data	O
via	O
NumPy	B-Application
types	O
(	O
and	O
therefore	O
support	O
vectorized	O
operations	O
)	O
,	O
and	O
present	O
a	O
more	O
Pythonic	O
interface	O
.	O
</s>
