Surface changes, 24 April 2004

On 24 April 2004, eight surface maps were made with RxH3 between 17h44 and 01h15 the next morning. The first seven maps were made at 80 GHz, the last map at 160 GHz. During the night the CSO tau was fairly constant at approximately 0.13.
A preliminary analysis of temperatures recorded during the maps is here.

The eight maps can be seen at map 1, map 2, map 3, map 4, map 5, map 6, map 7, map 8

Roof and doors were opened at about 17h12, but the first map could only be started at 17h44 due to problems with the new TCS and we had to use an older TCS-version.
Using the new, preliminary, masking of 80 GHz maps the following mean rms values were derived for the maps (see table below). Given are the average rms of the whole map (excluding the masked parts) and the adjuster rms. The time is for the middle of each map (with 80 GHz maps taking 50 minutes and 160 GHz maps 1 hour 50 minutes). Because of still unknown reasons the adjuster rms is larger at 80 GHz than at 160 GHz.

	freq	time	rms	rms(adj)
Map 1	80	18h09	32.9	36.6
Map 2	80	19h00	35.9	37.5
Map 3	80	19h50	31.8	34.3
Map 4	80	20h40	27.3	28.8
Map 5	80	21h30	26.5	28.4
Map 6	80	22h20	26.1	27.6
Map 7	80	23h10	28.1	29.4
Map 8	160	00h30	27.4	22.4

It can be seen that the rms was above 35 micron at the beginning of the night, with a maximum in the second map, and decreased until 26 micron. The rms of the 160 GHz map, 27.4 micron, is consistent with the rms of the previous 160 GHz map made 20 March (27.0) micron (no adjustment was yet made due to a problem with the adjuster micro). It appears that the rms after decreasing first, increases again after 23h.

Below are three series of plots showing the differences between the maps.
First I subtracted each map from the first map. The times indicated above the plots are again for the middle of the maps. All colour plots are scaled from -50 to +50 micron. It is seen that the differences develop a very characteristic diagonal pattern (from sector 2 to sector 8) which becomes a bit distorted in the last map (map 7 - map 1). Differences are of the order of -20 to +20 micron with larger values in some parts of the dish.
The second series of plots shows the difference between subsequent maps. Many of these plots show a striking striping pattern, possibly caused by standing waves which were not cancelled by the 16 frequency observations. These difference maps show decreasing values with maps 5 and 6 almost equal. But the next map shows again increasing differences. This reminds of the effects seen on 15 June 2002, where also the difference between the last maps again increased - see here (these maps were combined with tests of panel movements).

The last plot shows the difference between the 160 GHz maps of 24 April and of 20 March 2004.
Additional maps were made on 28 April at 80 and 160 GHz at about the same time as the maps 7 and 8 of 24 April. The difference between these maps is shown as well.

In the table below are the rms values of the difference maps.

	freq	rms	Q	Remark
Map 1-2	80	20.4	bad	arcs
Map 2-3	80	24.6	bad	arcs
Map 3-4	80	16.5	bad	arcs
Map 4-5	80	10.1	aver	few arcs
Map 5-6	80	10.8	aver	arcs
Map 6-7	80	12.0	good	deviation in sect. 6, 7?
Map 1-3	80	20.0	bad	arcs
Map 1-4	80	17.4	good
Map 1-5	80	19.7	good
Map 1-6	80	21.7	good
Map 1-7	80	23.9	good
2404-2003	160	22.3	aver	arcs
2804-2404	80	14.7
2804-2404	160	18.8

During all this maps temperatures were registered at about 200 locations in the dish every 6 minutes and I shall next analyse these measurements to see if they show any correlation with the changes in the surface. An analyses will appear here.