990304 report
Pointing: update central bearing solution (19990128)
MArch 04, 1999
A NEW 'EMPIRICAL' SOLUTION WAS INSTALLED AT THE TELESCOPE ON 04-MAR-1999 AT
12:33:27.23
Central bearing measurement - higher amplitude confirmed
The last measurement (
990220 ),
revealed a surprising increase in the amplitude of the c.b. defect.
To continue the monitoring of this effect, Mars was tracked using the
SCUBA map16 method, with the empirical corrections left enabled, from :
- (az,el) = (121/31) at 01:00 HST to (131/43) at 01:54
The pointing residuals are shown below :
The elevation pointing residuals, del have an rms scatter of 0.6".
The azimuth residuals clearly show the up and down signature of
the defect at about azimuth 125. With a correction for the baseline
trend, the daz residuals have a
peak-to-peak amplitude of ~8.5";
10.7" at the horizon.
It is (as on 990220 ),
in the sense of the empirical terms under-correcting the effect,
and confirms this most recent measure.
The new data are added to the
collection .
Based on the above measurement a new correction was derived and a new
new version of TEL_EMPIRICAL.DAT was installed today (3/04/99 12:33).
The plot below shows pointing data of 990304 without the
empirical correction in green,
with at the bottom the residuals (black
line) resulting from the empirical solution (black line, top) in use at the time of the
measurement. The red lines show the
new model and the new residuals: the horizon errors over the range of
the CB feature are within 1".
A WARNING: between 990128 and 990220 the effect changed from being
half of nominal to larger than seen before: the current peak-to-peak
effect is about 17.25"!
Please address any comments,
suggestions or requests to:
Iain Coulson
04 Mar 1999
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