Holography Run 2000 at the HHT

HHT 2000 Holography Run

Map Results

We are using the LES-9 satellite, provided by the Navy and MIT Lincoln Laboratory. This satellite has a 37 GHz transmittor, which the Navy let us use for 6 hours a day. The satellite normally supports communications (most notably to the south pole research stations).

Previous holography runs are summarized for 1998, 1997 and 1995.

Here we present log entries and representative holography maps. Each map covers the range of surface errors shown (early maps are of +/- 50 microns only). The total size of the maps (in pixels) is also given. The holography maps are made by measuring the signal from LES-9 as the telescope is scanned in a raster pattern. Along a raster line the telescope is scanned at a constant rate in either the azimuth direction or the elevation direction. In principle, the direction of the raster lines should be immaterial. There was no noticeable difference between the two kinds of maps in past years. Our maps this year were made in azimuth.

There are 3 rings. The center ring has 12 panels and the outer two rings have 24 each. Each panel has several positions around the edge or in the middle where it can be adjusted. The goal is to adjust the panels so that the RMS deviations from a perfect surface are less than 15 microns.

There is a quadrapod that supports a secondary reflector. It casts a shadow along diagonal lines. We get no information about panel positions here, but they don't matter since the light that hits them strikes the quadrapod legs. The legs also produce diffraction lines parallel to them that confuse the measurement. We have blanked out the shadowed region plus about an additional foot on either side in the maps below.

The accuracy of the maps depend upon the accuracy with which one can measure the phase of the radio waves entering the feed horn of the holography receiver. The feed horn introduces phase shifts that mimic misalignments of the telescope panels. We first correct the maps for these phase shifts. An improved measurement of the phase shift due to the horn was made this summer at the Georgia Tech Research Institute. The new measurement corrected some phase errors that caused some panels to be misaligned by 5-10 microns in 1998.

This animated GIF shows the daily progress of the 2000 holography session. For this animation we have used the averaged azimuth scans for various dates between 09/15-10/01/2000. The scale is +/-50 microns, as it is on all plots.

RMS of Ring 1 starts at 10.9 microns, finishes at 09.4 microns

RMS of Ring 2 starts at 13.7 microns, finishes at 10.0 microns

RMS of Ring 3 starts at 30.3 microns, finishes at 19.6 microns

Overall RMS of telescope starts at 22.7 microns, finishes at 15.17 microns

We achieved our goal of 15 microns rms over the entire dish surface!

See below for the individual plots.

We present below a sample of our averaged maps to illustrate how the the holography results changed with time and panel adjustments.

Map	Log Entry	Scan
Scale +/-50 Microns	Day 6 September 16, 2000
	Average of two 65 by 65 maps (5499 and 5575) taken on separate days. RMS of ring 1 = 10.9 microns RMS of ring 2 = 13.7 microns RMS of ring 3 = 30.3 microns Overall RMS of map = 22.7 microns	Average of scans 5499 & 5575 Sept 16, 2000 (65 by 65 map)
Scale +/-50 Microns	Day 6 September 19, 2000
	Average Map of Day 9 Sum of maps taken on same day RMS of ring 1 = 11.8 microns RMS of ring 2 = 13.8 microns RMS of ring 3 = 25.2 microns Overall RMS of map = 19.9 microns	Average Map of Day 9 5772 & 5807 Sept 19, 2000 (65 by 65 map)
Scale +/-50 Microns	September 19, 2000
	Average of scans from 3 days 5499+5575+5772+5807 This map is the pre-adjustment average RMS of ring 1 = 10.9 microns RMS of ring 2 = 13.7 microns RMS of ring 3 = 26.3 microns Overall RMS of map = 20.0 microns	Average of scans 5499+5575+5772+5807 Sept 19, 2000 (65 by 65 map)
Scale +/-50 Microns	September 20, 2000
	Average Map of Day 10 RMS of ring 1 = 11.5 microns RMS of ring 2 = 12.5 microns RMS of ring 3 = 33.8 microns Overall RMS of map = 24.7 microns	Average of scans 6058+6070 Sept 20, 2000 (65 by 65 map)
Scale +/-50 Microns	September 25, 2000
	Average Map of Day 15 6296 and 6329 Panel Adjustments Inner Ring Panels: 6,7,9,10 Middle Ring Panels: 8,13,19,20 Outer Ring Panels: 1,6,7,12,13,14,17,18,19,20,24 RMS of ring 1 = 10.6 microns RMS of ring 2 = 10.6 microns RMS of ring 3 = 18.9 microns Overall RMS of map = 15.1 microns	Average of scans 6296 and 6329 Sept 25, 2000 (65 by 65 map)
Scale +/-50 Microns	September 26, 2000
	Average Map of Day 16 Panel Adjustments Inner Ring Panels: 1,6,9,10 Middle Ring Panels: 1,2,5,11,14,17,20,23 Outer Ring Panels: 6,7,14,20,23 RMS of Ring 1 = 10.0 microns RMS of Ring 2 = 10.6 microns RMS of Ring 3 = 18.5 microns Overall RMS of map = 14.7 microns	Average of scans 6391 and 6424 Sept 26, 2000 (65 by 65 map)
Scale +/-50 Microns	September 30, 2000
	Average Map of Day 19+20 No panels moved. RMS of Ring 1 = 09.4 microns RMS of Ring 2 = 10.1 microns RMS of Ring 3 = 19.9 microns Overall RMS of map = 15.3 microns	Average of scans 6635+6694+6728 Sept 30, 2000 (65 by 65 map)
Scale +/-50 Microns	October 01, 2000
	Average Map of Day 21 Outer Ring Panels: 11 RMS of Ring 1 = 09.6 microns RMS of Ring 2 = 09.9 microns RMS of Ring 3 = 19.5 microns Overall RMS of map = 15.1 microns	Average of scans 6783+6818 Oct 01, 2000 (65 by 65 map)
Scale +/-50 Microns	October 01, 2000
	Grand Average Map of Day 20 and 21 This map is the post-adjustment average. RMS of Ring 1 = 09.4 microns RMS of Ring 2 = 10.0 microns RMS of Ring 3 = 19.6 microns Overall RMS of map = 15.2 microns	Grand Average of scans 6635+6694+6728+6783+6818 Oct 01, 2000 (65 by 65 map)

Created: 09/28/00
Last Changed: 10/03/00
contact: hbutner@as.arizona.edu

HHT 2000 Holography Run

Map Results

Map

Log Entry

Scan