Update on the Amplitude Calibration Issue Affecting some ALMA Data

Published: 11 Aug 2021
ALMA against the stars

ALMA has begun work on correcting some Cycle 7 interferometric datasets for a visibility amplitude calibration error that affects fields containing strong astronomical emission – details were described in this previous announcement. For all affected datasets with a >10% flux scale offset that have yet to be delivered, including those that will be observed in the remainder of Cycle 7 and in Cycle 8 2021, ALMA will apply a renormalization correction during data processing to correctly scale the amplitude calibration before being sent to PIs.

For affected datasets with flux scale offsets >2% but <10%, ALMA will provide renormalized data on request from the PI as needed. For affected data in the ALMA Archive, an investigation is underway and plans will be described in a future announcement. See the Knowledgebase article for details of the issue and the renormalization process. If you have any questions, or have comments or concerns, please contact your local ALMA Regional Center via the ALMA Helpdesk.