143 MHz, 340 meter baseline integrated data you can play with

[David Lonard]

Hello everyone,

I've finished a 30 day run with my 340 meter baseline interferometer centered at 143 MHz and a 10 MHz bandwidth. 21 out of 30 days were pretty clean during the night time, so I integrated this data to produce the attached figures. A pair of 3 element Yagis were used, pointed to the zenith. The field of view is very large for these antennas and the dominant fringes are likely coming from Cas A and or Sgr A in the late night/early morning when recorded in March/April.

Some important parameters for this data:

2D spectrograms are 1200 (Y-axis) x 400 (X-axis) bins

Y-axis is time, 20 seconds per row (6.666 hours of observation per sidereal day)

X-axis is frequency, 25 kHz per column

Vertical and horizontal blanks are places where I deleted RFI

Powerphase - a plot of the power and phase from a single 25 kHz channel

2D phase - 2D phase spectrogram of the visibility filterbank data

2D power - 2D power spectrogram of the same filterbank data

As you can see, the S/N is pretty good and the integrated data is small enough to post here. To play with this data yourself, you can use the attached file 'reader3.py'. You will need to save this file and 'binti.fit' on your local computer and make sure that the path is correct in the Python program. In the next message, retrieve the file named 'bintr.fit' as well. The reason for the two files is that one file contains the I and the other file contains the Q components of the complex visibility. The program will fuse this data into a complex visibility spectrogram.

By commenting in/out some of the lines of code, you can reproduce the images that I have attached. This is the complex visibility data that I will be using for my upcoming imaging attempts.

David

[David Lonard]

Here is the other part of the visibility data that you will need if you want to run the program.

[David Lonard]

I'm still working on gridding to get a better image of this data. In the mean time, here is a 2D delay/delay-rate 'image' of the visibility data taken from the padded 2D IFFT of the visibility filterbank.

What it shows is two fairly bright objects moving over in their positions across the sky over a 6 hour time frame (curved lines that draw incomplete ellipses).

In a properly gridded image, I would need to track one of the bright objects, repositioning it so that it doesn't move over time.