If
e = the total pointing error,
e
= the mechanical error,
e
= the error from the 7 parameters of
the pointing model,
e
= the encoder error,
e
= the thermal error,
e
= the tracking error,
e
= the error from noise in the FIVEPOINT measures,
e
= the error of inclinometry data,
e
= the error from the track model,
e
= the seeing,
then
e
= e
+ e
+ e
+
e
+ e
+
e
+ e
+ e
+
e
eqn. (1)
Assuming sufficient integration, good seeing, and estimates derived above for
e
, e
, e
, e
, e
and e
, equation (1)
becomes
e
= 0.5
+ e
+ 0.3
+ 0.5
+
0.1
+ 0.1
+ 0.3
+ e
+
0.3
i.e.
e
= 0.86 + e
+ e
Current pointing errors of 1.6
in each coordinate imply e
may be
as large as 1.4
, although MTPPN004 suggests values between 0.5 and
1.0 may be more appropriate. These imply e
has a value between
0.8
and 1.2
and may be the limit to the pointing accuracy.
In any case, arcsecond pointing requires e
<0.4
(rms).