Pointing errors after platform reinforcement

10feb11

The telescope beam reinforcement finished on 05feb11. The time line was:

11sep10 to 13oct10 - u2-u2l3 diagonal beam repair, reinforcement.
18nov10 to 05feb10 - reinforcement of vertical members.

This work added weight to the platform. The final distribution of new weight should be symmetric so the pointing should not be affected (other than the platform will now be lower at a fixed tiedown position).

After the work, pointing runs were done on:

07feb11: cband receiver, za limits still 16 degrees
08feb11: lband receiver, za limits 19.69 degrees.
09feb11: lband receiver, za limits 19.69

The plots show the results of the pointing runs (.ps) (.pdf):

Each page shows the za Errors vs za, az (top two frames) followed by the az Errors vs za,az (bottom two frames).
Page 1: 07-09feb11 pointing results:

This is after all of the work was completed. cband and lband was used.
The za error of B0320+053 near 20 degrees za (10asecs) is from the tiedowns going slack
The larger az errors below za=3deg is because the telescope is moving pretty fast in azimuth.

Page 2: 01dec10 thru 31jan11 pointing results:

This data was taken during the vertical member reinforcement. The za was limited to 16 deg. Cband and lband was used.

Page 3: 01dec10 thru 09feb11. all data separating out before after 01feb11.

The black points are 01dec1 thru jan11
The red points are 07,09 feb11.
there are no large differences below za=16 degrees.

Page 4: 01dec10 thru 09feb11. all data separating out lband and cband.

The black points are lband, the red points are cband.
They seem to track pretty well.

Page 5: the az, za coverage for the data

Top: 07-09 feb11
bottom: 01dec10 thru 31jan11

the results are summarized in the table below:

data set	offsets (asecs)		rms err (asecs)
	za	az	za	az
07-09feb11	-4.40	3.17	3.76	6.89
dec10-jan11	-5.06	0.35	5.23	6.11
All Data	-4.78	1.55	4.67	6.60

All Data (except B0428+205)	-4.60	0.73	4.79	5.87
All Data lbw	-5.25	1.85	4.51	6.19
All Data cband	-3.67	0.85	4.85	7.42

Summary:

The rms pointing errors after the beam repair are:

za=3.76, az=6.89 asecs

Using the dec thru feb data gives similar results.
Looks like an offset in za of about -5 asecs .
Removing the source B0428+205 reduces the rms to 4.79,5.87 asecs.
there is probably a small 1az term to be removed from the data.
Data from oct,nov10 did not have the -4.4 asec offset in za.
These offsets were not added to the pointing models (as of 20may11).

processing: x101/110204/x102..pro

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