mg002

MG002 Correlation Report

General:

• Session info: http://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/
• Station feedback: http://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/sessions/apr17/feedback_apr17.asc
• ALMA QA2: 2016.1.01116.V was used for polarization conversion
• This experiment has ALMA with 32x62.5MHz, VLBA with 2x128MHz channels, and most of the EVN with a 1x512MHz channel
• Two EVN stations (Yebes, Pico Veleta) observed in an incorrect backend mode, with a 32 MHz polyphase filterbank.
• Due to the issue at Yebes and Pico, three correlations were performed:
  • a) standard ALMA correlation setup (58 MHz bands) discarding Yebes and Pico
  • b) narrower band correlation setup (32 MHz bands) including Yebes and Pico
  • c) mixed-band correlation with additional postprocessing of all baselines to Yebes and Pico Veleta (reconstructed 58 MHz bands)
• The correlation output (c) appears correct, but uses a new feature that has not been vigorously tested. The data are provided without guarantees. Details are given further below.

Fringes:

Fringes plotted on all baselines to Effelserg (No0134 Effelsberg PDF), and ALMA (No0140 ALMA PDF), and VLBA only (No0200 VLBA FD PDF).

Notes:

1. In case (c) the additional processing consisted of, first, correlation with 58 MHz bands and several narrower bands that fitted the Pico/Yebes recorded bands (e.g., 32 MHz, 24 MHz, 2 MHz and similar), secondly, after correlation passing the visibility data through a post-processing script to form 58 MHz bands on the affected baselines using the narrow bands (i.e., combining visibilities in frequency domain from 32 + 24 + 2 MHz bands), thirdly, spectrally averaging inside the 58 MHz bands from 3712 channels per band to the final goal of 116 channels per band that matches the originally intended correlation mode.
2. Yebes began recording 20 seconds late in every scan
3. Pico restarted backend for scan 092-2100, bad sampler statistics in earlier scans