Pointing data obtained since the return of a 'wait' in mid-March are collected and analyzed. The plots below show the data with RxA, RxW_B, FE_HA (one receptor of HARP) and HARP (the centre of the array) obtained in the interval UT20070320-20070409:

Mean collimation adjustments have been applied as follows:

(CA,IE) = ( -0.6,  +4.7) for RxA
          ( +0.2,  -2.2) for RxW_B
          (+30.9, +50.8) for FE_H 
          (+14.7, +39.2) for HARP 

(2.0", 3.5"), (1.9", 3.1"), (2.6", 3.6") and (1.7",4.0"), respectively.

The scatters in dS are essentially as predicted when the model was installed, whereas those in dZ are disconcertingly large. Any underlying patterns are likely to be discerned only from the 135 RxA and 106 HARP-array data.

• The RxA plot (top) shows an increasing spread of dZ towards large zenith distance (centre subframe)- a phenomenon that may be explained by anomalous refraction. (The transparency of the atmosphere has been reasonably good for a large fraction of the period, and the humidity was often below 10%.)
• The HARP data (bottom plot) shows (in the corresponding subframe) a linear trend of dZ with Z that contradicts the above theory of anomalous refraction and demands a HARP-specific adjustment to the flexure parameter (TF) of about -12". This would reduce (dS,dZ) to (1.7",2.8").

There is no evidence to support changing the current RxA-based model, although a dedicated pointing run with RxA seems necessary to confirm its continued applicability. Some consideration must also seemingly be given to providing for HARP-specific model terms like TF.

Elevation residuals -vs- Leg Temperatures
Not since Feb 2006 have we been able to monitor the thermal component of the pointing. New logfiles now provide appropriate temperature data at the instant of each logged pointing measurement, and the results below for the RxA and HARP data show that the current algorithms are working reasonably well: