In recent EHT campaigns, data processing has been repeatedly slowed by issues related to ALMA QA2 calibration tables and polarization conversion (PolConvert). These issues often require multiple iterations between calibration, correlation, and analysis stages, leading to delays that can span months to years.

To address this critical bottleneck, a new ALMA QA2/PolConvert verification and troubleshooting procedure has been developed by Ivan Marti-Vidal and Ciriaco Goddi within the collaboration. This new workflow introduces an early-stage validation step, allowing potential issues in ALMA QA2 tables and polarization conversion to be identified within a short time after correlation, rather than late in the data analysis process.

Workshop Objectives

This workshop aims to train EHT members in the implementation of this new validation framework as part of the data processing within the C&E working group, including:

• Understanding procedure of ALMA-VLBI QA2 calibration and learning how to identify and resolve QA2 calibration issues.
• Running the PolConvert verification scripts developed by Ivan Martí-Vidal and Ciriaco Goddi, examining the polconversion quality of EHT2024 data.
• Diagnosing common failure modes in polarization conversion
• Identify the bands/tracks of the EHT2024 data that would allow for robust M87 imaging based on polconverted data.

Participants will gain hands-on experience with a prototype end-to-end verification pipeline, covering:
QA2 → PolConvert → rPICARD → Diagnostics → Troubleshooting

Why This Matters

The new QA2/PolConvert validation workflow is expected to:

• Dramatically reduce iteration cycles in EHT data processing
• Enable early identification of ALMA QA2 and polconversion issues
• Allow the collaboration to move toward faster and more robust L1 data releases

Instructors and Contributors

This workshop will be led by experts in Polconvert, ALMA QA2, and EHT calibration, including :

• Ivan Martí-Vidal (Polconvert Verification Procedure)
• Hiroshi Nagai (ALMA QA2 Calibration)
• Hugo Messias (ALMA-VLBI QA2 Calibration; on-line participation)
• Michael Janssen (CASA/rPICARD support)

Location

9F, Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Taipei, Taiwan

Agenda

Detailed agenda will be announced soon. The workshop will include half a day for excursion in Taipei.

Contact Person

Cheng-Yu Kuo (NSYSU/ASIAA)
Email: cykuo.tarag-mail.nsysu.edu.tw