Pointing measurements

We have tested the performance of the Plateau de Bure antennas by doing repeated pointing measurements on strong sources. The measurement technique was either cross scans of about 30 seconds duration, or five point maps with 10 second integrations on each of the five points. After each measurement the pointing corrections were updated. Focusing was also done on the same sources.

The sources were 2230+114, 3C454.3, 0923+392; their fluxes were in the range 4 to 6 Jy. The measurement errors were 0.12-0.20'' for the five point method and 0.25-0.50'' for the cross scan method. The results are summarised in Table 3. Only four antennas were available. The measured pointing errors show a slow drift (a few seconds per hour), and short term fluctuations. The results are shown in Figs. 1 to 5. For each day I have computed the residual r.m.s. deviation after removing a polynomial baseline (linear for the short experiments, of degree 2-4 for the long ones).

 

 

night Seeing(Az) .31 Seeing(El) .40

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .38 .70 .36 .48 .48 .41 .71 .94

Tracking rms .57 .37 .33 .76 .35 .23 .27 .18

Measurement rms .52 .44 .20 .26 .38 .23 .23 .24 20 Sep.

noon Seeing(Az) 2.90 Seeing(El) 3.56

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms 2.13 1.43 2.42 1.64 2.71 3.35 3.89 3.17

Tracking rms .36 .25 .25 .46 .35 .29 .31 .25

Measurement rms 1.18 1.01 1.02 .98 .98 .95 .94 .98 21 Sep.

sunrise Seeing(Az) .69 Seeing(El) .71

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .83 .60 .85 .40 1.06 .96 2.27 .93

Tracking rms .38 .27 .27 .39 .39 .28 .30 .29

Measurement rms .53 .46 .23 .22 .36 .30 .29 .42 21 Sep.

day Seeing(Az) 3.21 Seeing(El) 4.23

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms 2.61 2.12 2.76 2.46 3.11 2.94 2.80 3.14

Tracking rms .38 .27 .27 .39 .39 .28 .30 .29

Measurement rms .73 .70 .54 .58 .61 .52 .55 .60 25 Sep.

day Seeing(Az) .69 Seeing(El) 1.01

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .51 .65 .94 .34 1.40 1.00 1.29 1.05

Tracking rms .47 .58 .26 .67 .20 .13 .23 .18

Measurement rms .12 .12 .12 .12 .12 .12 .13 .12

 

 

night Seeing(Az) .59 Seeing(El) .69

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .84 .65 .74 .37 .83 .58 .82 .79

Tracking rms 2.67 .49 .29 .79 .35 .22 .55 .45

Measurement rms .12 .12 .12 .12 .12 .12 .13 .12 29 Sep.

noon Seeing(Az) 1.54 Seeing(El) 1.57

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .63 .85 .62 .74 1.15 .77 1.10 .92

Tracking rms .54 .52 .29 .60 .28 .26 .21 .19

Measurement rms .14 .13 .14 .14 .14 .14 .15 .14 29 Sep.

afternoon Seeing(Az) 3.19 Seeing(El) 3.42

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms 1.19 1.66 2.02 1.89 1.90 2.42 2.27 1.47

Tracking rms 1.25 .42 .40 .60 .38 .32 .39 .30

Measurement rms .14 .15 .16 .15 .15 .15 .15 .15 01 Oct.

night Seeing(Az) .50 Seeing(El) .54

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .52 .57 .36 .47 .83 .72 1.33 .84

Tracking rms 1.12 .60 .34 .83 1.02 .26 .31 .22

Measurement rms .18 .18 .19 .19 .18 .18 .19 .18 01 Oct.

night Seeing(Az) .66 Seeing(El) .76

Axis Azimuth Elevation

Antenna 1 2 4 5 1 2 4 5

Pointing rms .59 .56 .84 .71 .77 .71 1.08 .71

Tracking rms 2.11 .40 .39 1.03 .95 .31 .55 .33

Measurement rms .18 .18 .19 .19 .18 .18 .19 .18

  
Figure 1: September 19th data

  
Figure 2: September 21st data

  
Figure 3: September 28th data

  
Figure 4: September 29th data

  
Figure 5: October 1st data. The wind direction was almost exactly North; The antennas were pointed to the South-West at 40-60 degrees elevation.