CIMA / WAPP examples for pulsar observations

Setup:

In observer2, go to an "xterm" and type "CIMA". If you are at AO, you can also move the mouse to the left screen, click on the background with the right mouse button and select ``CIMA''.

If observing remotely, the controller will have to grant you permission to observe (this is done according to the telescope schedule).

On the first window that comes up ("Identify New User"), answer THREE QUESTIONS:

Your name
The project number (as on the schedule, with lower-case letter)
The type of observation (in this case, click on ``Pulsar'' button)

In what follows, the setup might seem to be a bit strange. This happens because CIMA is in a state of flux. There are several new features (like the "NEW AND IMPROVED IF/LO SETUP") which are a) guaranteed to work for any frequency and b) will soon become the basis of CIMA. So you should become acquainted with these as soon as possible.

The setup occurs in three phases; that will eventually converge in three relevant widgets: Pointing, IF/LO setup and Back-end setup. Telescope setup should occur in this order.

Pointing:

After starting CIMA, a window shows up asking you to select the receiver ("Choose Receiver"). Select your receiver at this stage.

Go to CIMA observer's Interface:

... and click on "pointing control". The following widget will appear:

With the left mouse button, select the pulsar you want to observe, and then click ``point''. If the telescope does not start moving, click again. If still the telescope does not start moving (as seen in the "aostatus" display), ask what is happening to the operator. After he tells you to proceed, issue the command again.

Now, while the telescope is moving, you have time to setup the IF/LO system.

IF/LO setup:

Go to CIMA Observers' Interface and press on the RECEIVER IF/LO control button! The following widget will appear:

You don't have to worry about any of this, with one exception. Click on the "New Improved IFLO setup" button. The following widget will appear:

Image of ew Improved IF/LO control widget

Using the pulldown menus, select:

The receiver
The polarization (for a few receivers, like L-wide, one can choose between linear and circular polarizations, for other receivers this is not available)
The front-end filterbank (for L-wide, I normally choose the 1120-1220, 1320-hipass filters; this creates a notch between 1220 and 1320 MHz which excludes a lot of very strong RFI from radars like Punta Salinas). Again, a front-end filterbank is not available for all receivers.
The IF path from the Gregorian to the control room (for new projects, this should be chosen as 10GHz to 1500; this has several advantages, like keeping the LOs of the band being observed, and a very large bandwidth). Until now, the 750 MHz path was used for L-wide and 750-MHz narrow was used to the low-frequency receivers. Now, the 750-narrow is still strongly recommended for the receivers below 1 GHz, for Lband and above, we recommend 10GHz ro 1.5.
Select destination. The WAPP is the normal destination. However, one might want to use the WAPP in parallel with other backends. Details here.
The central frequencies for the 4 WAPPs
The bandwidths for the 4 WAPPs.
Optional: Press the "Show these Choices" button. This will show you a screen like that produced by "rxview". You can see in that screen if LOs are in your passbands, and other useful information.
Press button that says "Apply this setup". You should be ready to go. The view given by "rxview" will become similar to what you saw in the previous line.

The reason why the WAPP bandwidths have to be chosen at this point is the following: If the bandwidth selection is 100 MHz, the WAPPs accept incoming signals at 250 MHz. If the bandwidth selected is 50 MHz or smaller, then the WAPPs accept incoming signals at 275 MHz. This information is needed to calculate the LO frequencies.

If you like the present configuration, and if it takes time to setup and if you have taken time testing it, then you might want to save it. You can do this by clicking on the "Save Configuration" button.
You can recover this later by clicking on the "Load configuration" button.

Back-end setup:

The telescope is now driving towards the pulsar, so you have time to set up the WAPPs. On CIMA Observer's Interface, click on the ``pulsar observing'' button. A window shows up with the ``WAPP datataking control GUI''.

For this to proceed well, you have to ignore the following buttons, which will soon disappear: "Bandwidth", "Frequency" type-in box and the "Setup IFLO button". All these things have been defined already by the "New Improved IFLO Control".

On WAPP1, select: number of lags, sampling time, and the type of voltage sampling (3 or 9 level).

Important: The ratio between number of lags and number of microseconds in the sampling time should not exceed 4 (for 3-level, no polarization mode)! Otherwise, the data rate is too fast, and the machine becomes unstable.

Then push button that says ``Copy WAPP1 to all''. For arbitrary choices of number of lags, press on the button that says, e.g., "WAPP2", and type in the number of lags and sampling time there.

On the WAPP datataking control GUI, Click on the ``sanity check'' button

IF everything is alright, go to the next step.
IF one of the WAPPs is not responding, open another xterm, slogin to the wapp that is not responding as "wapp"
> slogin wapp2 -l wapp
type in the password (wappme), and then type ``start_wapp''.

Press the ``monitor'' in the WAPP Datataking Control GUI.

To be able to ``monitor'' the signal, you must have the WAPPs on ``search'' mode. If you swicth to ``timing'' or ``sampler'' (a mode that can do baseband sampling), you can no longer monitor the signal.

The power levels should appear in the WAPP Datataking control GUI, in the position where before you could see the letters "(a)(b)" (Just below the frequency box).. They should not be too far (in a logarithmical sense) from 1.

Press ``auto-attenuation'' in the WAPP Datataking Control GUI. See if both channels for all WAPPs come to within 1 dB of 1.0

To check the band and the RFI, go to the "snap" display and press the button that says "continuous".

Select the WAPP you want to look at from the menu in the upper left (by default it starts with WAPP, which is the same as WAPP1)

In the lower plot of ``snap'', you can select the total power or ``bandpass''. The right plot is a waterfall plot, showing time in the horizontal axis and frequency in the vertical axis for the two polarizations.

If the levels of the WAPPs are not 1.0 (i.e., if they are either too low or too large after clicking on the "Auto Attenuation" button on the WAPP Datataking Control GUI, then go to the Receiver IFLO control widget. Without stopping the monitorization, click on the ``Advanced IF power control''. The following widget will appear:

Image of Advanced IF power control widget

ATTENTION NEEDED: in the column labelled "Atten (act)", in blue, are the PRESENT VALUES. In the column called called "Atten(cmd)" are the values you are going to send. For IF1A and IF1B, copy the blue numbers into the box. For IF2A and IF2B, you can change the total attenuation to solve your IF power problem (try typing in "0" for both columns.

Press "Send this configuration" button. See what happens to the power levels in the WAPP Datataking Control GUI.

In the WAPP Datataking Control GUI, press ``Auto-attenuation'' again. Keep adjusting IF2 attenuators until everything converges to a value near 1.0.

End the Monitoring: Press ``stop observation'' in the WAPP Datataking Control GUI. Monitoring is like any other observation, so it must be stopped like if it was a normal observation.

Wait until the telescope reaches the pulsar (if it has not reached it already).

In the WAPP Datataking Control GUI, select the observation time. If you want to observe for an amount of time different than the choices available in the pull-down menu, you can press the ``Set run time'' button and type in the amount of time.

End of setup stage. Now do observation in "search mode", "timing mode" or "sampler mode".

IF/LO setup for simultaneous observations with the WAPP and other backends:

After starting the CIMA session, do the normal IF/LO setup until the "New and Improved IFLO" setup stage. This is repeated below:

After starting CIMA, typing in observer's name, project number and "pulsar", a window shows up asking you to select the receiver ("Choose Receiver"). Choose your favourite receiver.

Point the telescope.

Go to CIMA observer's Interface and press on the RECEIVER IF/LO control button! The Receiver IFLO Control widget appears.

You don't have to worry about any of this, with one exception. Click on the "New Improved IFLO setup" button. The New Improved IFLO Control widget appears.

Using the pulldown menus, select:
1. The receiver
2. The polarization (for a few receivers, like L-wide, one can choose between linear and circular polarizations, this option is not available for all receiver)
3. The front-end filterbank (available for some receivers, like L-wide and S-wide).
4. The IF path from the Gregorian to the control room (Recommended: 750 Narrow for receivers below 1 GHz, 10GHzto1.5 for L-band and above).
5. Select destination.
6. Set the central frequencies and bandwidths for the usable WAPPs.
7. Optional: Press the "Show these Choices" button. This will show you a screen like that produced by "rxview". You can see in that screen if LOs are in your passbands, and other useful information.

From here on, you can do the WAPP setup to do a search observation, timing observation. Just keep in mind which WAPPs are being fed the wrong frequencies.

Last updated: Nov.2 2004
Paulo Freire