Difference between revisions of "Owen's Notes"

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(Reference Calibration)
(Phase Calibration)
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=== Phase Calibration ===
 
=== Phase Calibration ===
  
After the reference calibration has been done, the phase calibration can be performed. Click on a good calibration (one that has not had a windscram and has a reasonable duration).
+
After the reference calibration has been done, the phase calibration can be performed. Click on a good calibration for the high band (one that has not had a windscram and has a reasonable duration). Not that Phase Cals are not performed using the low band.
  
The click on 'Analyze as Phasecal'. At the top of the screen click on the 'Sum Pha' tab. The important thing here is that the slopes look good.
+
Then click on 'Analyze as Phasecal'. At the top of the screen click on the 'Sum Pha' tab. The important thing here is that the slopes look good. Below is an example display of the slopes.
  
 
== Update Antenna Pointing (17 March 2020) ==
 
== Update Antenna Pointing (17 March 2020) ==

Revision as of 15:16, 31 March 2020

Remote Login (23 March 2020)

The computers can be accessed remotely using SSH and VNC. Since I use Linux (Ubuntu) these instruction are for that OS.

To VNC into Helios, open a terminal and type the following command:

ssh -L 5902:helios.solar.pvt:20000 oweng@ovsa.njit.edu

I then open Remmina Remote Desktop Client. Make sure VNC is selected at the top left. Type in:

localhost:2

and enter the password when prompted.

The Helios display should now be visible.

Occasionally, the VNC connection will be lost. If this occurs the following procedure need to be performed.

From a new terminal window type:

ssh -L 8887:helios.solar.pvt:22 oweng@ovsa.njit.edu

From another terminal issue the command:

ssh -p 8887 sched@localhost

Now type in:

x11go

Now restart the VNC client.

Phase Calibrations (23 March 2020)

Phase calibrations are to be performed every day when possible.

Reference Calibration

Before the phase calibration can be done, a reference calibration needs to e performed, which will be subsequently used as the reference for the phase calibration.

Access the Helios computer.

On the terminal window make sure that the ipython: /home/user tab is selected.

There should be a prompt as follows: pipeline:~>

At the prompt type the following command:

python /common/python/current/calwidget.py

The following window will open up:

The calwidget window.

In the date box near top right of the window type in or use the up and down arrows to select the previous days date and hit enter.

Click on the first available scan that does not suffer from a Windscram. Windscrams are marked in red. If a windscram occurred for less than 20% of the scan then it will be marked in yellow and may still be usable. The example below shows a windscram at 22:14:05.

The calwidget window with windscram shown at 22:14:05 highlighted in red.

Select the earliest calibration that does not have a windscram, and then click on 'Analyze as Refcal'. The Sigma map should now be populated as shown below:

The calwidget window with sigma map. It also shows power and phases for Antenna 1 and Frequency Band 12.

The above chart is for the low-band (channels 1 to 12). Yellow blocks indicate bad or unavailable data. Bands 3 and 4 are excluded due to intense RFI at these frequencies. Antenna 5 currently is not operating well, and will be excluded from any analysis. The green blocks indicate that the data may be alright if some points are excluded. Purple blocks indicate the data is good.

Also shown in the above plot is the power and phase for Antenna 1 and band 12. The blue points are the X-polarization and the orange points are the Y-polarization. These should be close to straight lines.

In this case we need to exclude all of Antenna 5 from the calibration. First click on any block for antenna 5 in the range of band 1 to 12. Next check the box 'Apply to all bands'. Move the mouse over to either the Power or Phase plots (either works). We need to exclude all points. Move the mouse slightly before the first point in the chosen plot and press the 'A' key. A green line will appear. next move the mouse slightly past the last point and press the 'B' key. A red line will appear. The screen should look like the figure below.

The calwidget window with antenna 5 having all points flagged for all bands.

Now click on 'Apply time flagging. All of antenna 5's bands should turn yellow.

Once complete, select the associated high band calibration and then click on 'Analyse as refcal'. In this case bands 7 to 52 will be shown on the sigma map as shown in the figure below.

The calwidget window with sigma map. It also shows power and phases for Antenna 8 and Frequency Band 34.

Antenna 5 once again needs to be excluded using the procedure described above. In addition antenna 13 has problems from band 13 to 52. We will remove these channels from the analysis. Ensure 'Apply to all bands is unchecked and select 'Apply to all bands above selected one'. Select band 13. As before select all of the points by pressing 'a' and 'b' at the appropriate points (start and end of the plot). Click on 'Apply Time Flagging'. All of the bands from the selected band up should turn yellow as shown in the figure below.

The calwidget window with Antenna 5 excluded and most of Antenna 13 excluded.

As can be seen, there are still 3 green squares. We can make these good by selecting each one and flagging bad samples. In this example I have selected Antenna 4, Band 23.

Ensure all checkboxes are unchecked. Slelect the box for the antenna and band the you wish to time flag. select (using mouse and a and b keys) up to two ranges of points to exclude. pressing the x key will remove the most resent line chosen. Once you have flagged the ranges, click on 'Apply Time Flagging'. Hopefully the box will turn purple. If not you may need to select different ranges.

The result of this procedure is shown below.

The result of time flagging an individual antenna and band. Antenna 4, Band 13 is now purple.

Repeat this procedure for the remaining bad antennas and bands.

Once completed, select one of the bands of the refcals from list on the left and then click on 'Set as Refcal'. The click on extend selection. NOw select the other refcal. Make sure both are highlighted. Click on 'Set as extended refcal'. Click on 'Save to SQL'.

Phase Calibration

After the reference calibration has been done, the phase calibration can be performed. Click on a good calibration for the high band (one that has not had a windscram and has a reasonable duration). Not that Phase Cals are not performed using the low band.

Then click on 'Analyze as Phasecal'. At the top of the screen click on the 'Sum Pha' tab. The important thing here is that the slopes look good. Below is an example display of the slopes.

Update Antenna Pointing (17 March 2020)

Access the Pipeline Computer.

From the terminal, start ipython:

ipython --pylab

Import the calibration and Time libraries:

import calibration as cal

from util import Time

Load up the solar pointing scans for a given date and time.

x,y,qual=cal.solpntanal(Time('2020-03-17 18:30'))

The above command will load the scans from the 17 March 2020 18:30 UT.

To view the beam widths as a function of frequency for each antenna and polarisation:

cal.sp_bsize(x,y)

An example of the X-beam widths for each antenna
An example of the Y-beam widths for each antenna

To obtain the pointing offsets:

xoff,yoff,dx,dy=cal.sp_offsets(x,y)

This will display the offsets for each antenna and feed. Ideally the offsets should be at zero. If particular antennas significantly deviate from zero then a correction can be made.

For example, the following command will adjust the pointing offsets for antennas 6 to 8, 10 and 13:

cal.offsets2ants(Time('2020-03-17 18:30'),xoff,yoff,antst='ant6 ant7 ant8 ant10 ant13')

The newer antennas with the alt-az drives that have had tracking updated will need to be rebooted. From the Schedule Window issue the commands:

reboot 1 ant6-8

tracktable sun_tab.radec 1 ant6-8

track ant6-8

The antenna pointing adjustment is typically performed once per month.

Helios Displays

The Schedule window show the currently running schedule as shown below.

The Schedule Window

The left side of the window shows each of the scripts that is to be run. The orange bar shows the task that is currently being run.

The right side of the window shows each command that is to be run in the current script.

At the bottom of the window are a series of buttons. The STOP button will stop at the current script. Once stopped, the remaining buttons will become active.