Temperature changes, 24 April 2004 and
comparison 20 - 29 April

The temperatures are recorded every 6 minutes in about 180 sensors (which are not all functional) in different parts of the dish:
Conebars (12), Coneheads (12), Spinebars (12), Bifurcated beams (8), Backing structure (7 in each of the 12 sectors of the dish), Square (8), A-Frame (16), Centerbeams (16). Elevation Ring (2), Counterweight (2), Ambients (8).
This page shows some results of these measurements on 24 April 2004, which can be compared with the RxH3 maps:

1. The location of the 12 sectors of the dish as seen from UKIRT.

2. The ambient temperature recorded by the weather station in the well behind the doors but in front of the membrane. The doors were closed at about 10h20 HST and opened again at about 17h12 which resulted in a slight increase in temperature. Two plots are for the period HST 0h - 24h and 16h - 24h.

3. Five figures show the change in temperature between 0h and 24h HST for the 180 sensors in the above mentioned parts of the dish. The more massive parts (e.g. counterweight) have only small temperature variations whereas other parts show large variations similar to but not equal to those of the air temperature: the maximum is at the end of the afternoon rather than in the morning. The centerbeams show rather deviant changes: these sensors are located in the four (partly) isolated columns in the cabin at different height. Some of the backing structure sensors show a sharp cusp just after the doors were opened, and in some sectors of the dish they show almost equal temperatures during the day but a gradient where the temperatures increase from the outer edge to the inner part of the dish.

The next plots show an analysis of the average temperatures of sensors during the seven 80 GHz RxH3 maps which were made between 17h44 and 23h54. Each data point is an average of eight temperature measurements. This is done for the sensors on the conebars, coneheads, spinebars, and in the 12 sectors of the backing structure (112 sensors). For the conebars, coneheads, and spinebars the sensors are ordered according to sector number from 1 to 12. In each of the backing structure sectors the sensors are approximately (this still has to be checked in more detail) ordered from the inner ring to the outer ring of the dish.
Shown are the following plots:
4. The average temperature during each of the seven maps.
5. The temperature difference with respect to map 1 (left) and the difference of the derived moves wrt map 1 (right). Within a sector moves are plotted from the outer ring to the inner ring of the dish (opposite to the temperatures)
6. The temperature (left) and derived moves difference (right) between two subsequent maps.

Below these plots follows a analysis of the recorded temperatures for the period 20 - 29 April 2004.

An important conclusion from the figures 3 and 4 seems to be that the temperature distribution during RxH3 observations (at 8.5 degrees elevation) is significantly different from that on other days. This is the case on 24 April when the telescope was pointing towards UKIRT during the whole first shift. On 28 April also holography was done. However it was preceded by 5.5 hours of normal observing and the effect of the holography on the measured temperatures apparently is much less.