  New analysis is presented of the 1.1 mm wavelength absorption lines in Venus'
atmosphere that suggested the presence of phosphine. We retrieve a sulphur
dioxide observation from the JCMT archive that was simultaneous within a few
days of the PH3 1-0 spectrum obtained in June 2017, and demonstrate via a
radiative transfer calculation that contamination of PH3 by SO2 was ~10 per
cent. We also present ALMA 2019 spectra of PH3 1-0 and an SO2 transition
acquired simultaneously, and infer that SO2 line-contamination was ~2 percent
(for the least-noisy half of the planetary disc). The contamination-subtracted
ALMA and JCMT spectra (of 6-8 sigma confidence) are now consistent with similar
absorption-depths at the two epochs. The two values span -1.9(+/-0.2) 10-4 of
the continuum signal (which was re-estimated for ALMA), albeit for differing
planetary areas. This suggests that the abundance attributed to phosphine in
Venus' atmosphere was broadly similar in 2017 and 2019.
