SUMMARY
Despite poor weather, sufficient pointing data were obtained to recover the pointing model, and tracking data on Mars show no signs of the old (central bearing) defects. However, all of this could bear repeating under more stable conditions.

All-sky Pointing
33 data were collected between 20:50 and 23:10 as shown below left. The data were run through FIT7 to yield radio_telescope.dat;489 which was created and installed at 01:00 on the 13th. The expected rms scatters in (daz,del) from this model are (1.7",2.1")

This new model was tested later when 39 data were collected between 02:30 and 06:30; these data are shown above, right. The scatters remain large, but the sky conditions deteriorated throughout the run. However, this model should suffice to enable observing to resume.

Tracking
Tracking is done so as to reveal defects such as those due to the central bearing.
The weather was not ideal for this test - thick cirrus everywhere, tau_cso was tolerably 0.1 or so, but the seeing was variable and never less than 0.5".

Tracking of Mars was done using the SCUBA map16 method. There were no empirical corrections ! The data were obtained in three chunks :

• between 19:48 and 20:43, where (az,el) = (121,38) to (133,48)
• between 23:12 and 01:02, where (az,el) = (195,59) to (232/44),
• between 01:03 and 02:24, where (az,el) = (232,44) to (246,28).

The second dataset is broken in two to create plots with similar azimuth ranges, and the data are adjusted internally by their mean values for display purposes, although, of course, the latter lot form one continuous dataset :

The data show some strong baseline drifts, which are not easily ascribed to the weather or to defects in the 7-parameter telescope model. But there is no indication of residual defects at azimuths 125, 209, 225, 240 of the type seen with the old central bearing. As with the all-sky pointing, the experiment should be repeated in better weather conditions.

A repeat
Further data was obtained the following evening :

• between 19:45 and 21:27, from (az,el) = (121,38) to (148,55)

Again the seeing was typically 0.7", which explains the internal noise. The baseline drift is not explained at this stage, but it is of the same size as seen in this azimuth range previously (above). Again, there is no sign of defects at azimuths 125 or 140.

Another repeat
Further data was obtained on the morning of the 16th May HST :

• between 01:16 and 02:13, from (az,el) = (238,39) to (247,27)

There is no sign of defect at azimuth 240.