Introduction

Measuring the azimuth track profile using inclinometry is usually taken with the antenna servo-ed close to zenith, since the inclinometer in the cabin is fixed to the TMU support structures. It needs to be within a couple of arcminutes of horizontal to stay within its operating range. Since the pointing corrections derived from the track profile are applied at all elevations it has been a long-standing anomaly that we have only collected track profile data with the antenna in one position. The introduction in the past month of another inclinometer mounted on the adjustable part of the tertiary mirror unit allows this inclinometer to be tilted to compensate for the elevation of the antenna, and so to obtain track profile data at any elevation. The loading of the antenna on the track has been considered sufficiently 'dynamic' that some variation may be expected.

Data

A normal CW run was done with the 'old' (fixed) TMU inclinometer on 05 Oct and data were taken on 06 Oct with the new, tiltable inclinometer. Full CW runs were planned at elevations = 60 and 30, but some TCS faults limited the data to quadrants 1, 2 & 5 (all in the east) as will be seen below. These data are compared below, data channel by data channel, with the previous successful track profile measurements of 21 Sep :

TX	TY
LX	LY
RX	RY

At first blush there appear to be no large changes in the inclinometry data as the elevation changes. Small scale structural differences certainly appear to be of very small size, while large scale effects are limited to the channels LX & RX which are not used in the creation of the track model.

Quantification of the apparent similarity must await completed datasets.