PAPER Polarimetry Observing Procedures

Software downloads

You can obtain the software mentioned below from the Github folder here: PAPER Polarimetry Project Repo

Running the observations

First Light

Before running your first observation with the PAPER antenna system, you will want to download the programs dsp-flowgraph.py (a GNU Radio Python script) and rpi_client.py and save them in your home directory on Maia. You will then want to create a /bin folder in your home directory and save the bash script run_dsp to that folder, and make it executable.

Next, ssh into Soyuz and the Raspberry Pi from Maia. You will want to have the program rpi-sensor-data.py saved to your home directory on the Pi, and you will want to have the GRC file ettus-test.grc saved in your directory on Soyuz. You are now ready to prepare for and start observing.

Running an Observing Session

There are a number of steps to perform prior to starting up each observation:

• Set the observing interval (total time to observe) by changing the number of seconds to observe in the interval variable in line 251 of dsp-flowgraph.py, and in line 8 of rpi_client.py. Default is 24 hours.
• Set the integration time by changing the value of the variable int_size on line 47 of dsp-flowgraph.py, which sets the decimation in GNU Radio. Note that this value does not correspond directly to the number of seconds to integrate over -- see more on this in the section "Problems / potential improvements". The default value is 16380, which corresponds to roughly 3 minutes integration time.
• Set the RPI sensor reading frequency by changing the variable INT_TIME on line 12 of rpi-sensor-data.py to the number of seconds you want between each sensor reading. Default is 5 minutes.
• VERY IMPORTANT: Change the filenames of the data session you want to save by changing the data filenames given in lines 90 and 92 in dsp-flowgraph.py.

After these initial steps have been completed, follow these steps to run the observation:

• On the Raspberry Pi, run the command python3 rpi-sensor-data.py
• On Soyuz, run the ettus-test.grc flowgraph.
• On Maia, run the command run_dsp. You should see an initial message and after a few minutes, data readings from the sensors should show up on the terminal display.

If you run into problems, contact me at elliewhite1420@gmail.com.

Processing the observations:

First, download the programs dataGraphing.py, tempCorrections.py, getCoeffs.py, and the S-Parameter data files (the s2p files) to the same directory. In dataGraphing.py, change the variables infile_a (line 21) and infile_b (line 22) so that the filenames match the filenames of the data you recorded for Channel A and Channel B respectively (Channel A is N-S polarization, B is E-W). Change the rpi_filename (line 25) to the name of the RPI metadata file produced during your observation (this filename is printed in the terminal after you run the observing command). You should now be able to run python3 dataGraphing.py and obtain plots of antenna temperature vs. time, with temperature corrections applied.

Problems / potential improvements

One main issue that was encountered when developing the data acquisition system was difficulty in calculating the decimation value that corresponds to a given integration time in seconds. Another problem is that when observations are attempted with larger decimation rates than somewhere around 16380, the flowgraph does not store any samples at all. This problem is not well understood by me, and would benefit from further investigation / experimentation.

-- EllieWhite - 2019-09-05