<s>
In	O
ballistics	B-Application
and	O
flight	O
dynamics	O
,	O
axes	B-Algorithm
conventions	I-Algorithm
are	O
standardized	O
ways	O
of	O
establishing	O
the	O
location	O
and	O
orientation	O
of	O
coordinate	O
axes	O
for	O
use	O
as	O
a	O
frame	O
of	O
reference	O
.	O
</s>
<s>
Finally	O
,	O
in	O
case	O
of	O
space	O
vehicles	O
like	O
space	O
shuttles	O
etc.	O
,	O
a	O
modification	O
of	O
the	O
latter	O
convention	O
is	O
used	O
,	O
where	O
the	O
vehicle	O
's	O
(	O
body	O
's	O
)	O
positive	O
y	O
-	O
or	O
pitch	O
axis	O
again	O
always	O
points	O
to	O
its	O
right	O
,	O
and	O
its	O
positive	O
z	O
-	O
or	O
yaw	O
axis	O
always	O
points	O
down	O
,	O
but	O
“	O
down	O
”	O
now	O
may	O
have	O
two	O
different	O
meanings	O
:	O
If	O
a	O
so-called	O
local	O
frame	O
is	O
used	O
as	O
external	O
reference	O
,	O
its	O
positive	O
z-axis	O
points	O
“	O
down	O
”	O
to	O
the	O
center	O
of	O
the	O
earth	O
as	O
it	O
does	O
in	O
case	O
of	O
the	O
earlier	O
mentioned	O
NED-system	O
,	O
but	O
if	O
the	O
inertial	O
frame	O
is	O
used	O
as	O
reference	O
,	O
its	O
positive	O
z-axis	O
will	O
point	O
now	O
to	O
the	O
north	O
celestial	O
pole	O
,	O
and	O
its	O
positive	O
x-axis	O
to	O
the	O
Vernal	O
Equinox	B-Application
or	O
some	O
other	O
reference	O
meridian	O
.	O
</s>
<s>
in	O
order	O
to	O
perform	O
certain	O
astronomical	O
observations	O
,	O
the	O
preferred	O
reference	O
is	O
the	O
inertial	O
frame	O
,	O
and	O
the	O
RPY	O
angle	O
vector	O
(	O
0|0|0	O
)	O
describes	O
an	O
attitude	O
then	O
,	O
where	O
the	O
shuttle	O
's	O
wings	O
are	O
kept	O
permanently	O
parallel	O
to	O
the	O
earth	O
's	O
equator	O
,	O
its	O
nose	O
points	O
permanently	O
to	O
the	O
vernal	O
equinox	B-Application
,	O
and	O
its	O
belly	O
towards	O
the	O
northern	O
polar	O
star	O
(	O
see	O
picture	O
)	O
.	O
</s>
<s>
(	O
Note	O
that	O
rockets	O
and	O
missiles	O
more	O
commonly	O
follow	O
the	O
conventions	O
for	O
aircraft	O
where	O
the	O
RPY	O
angle	O
vector	O
(	O
0|0|0	O
)	O
points	O
north	O
,	O
rather	O
than	O
toward	O
the	O
vernal	O
equinox	B-Application
)	O
.	O
</s>
