The aims:   

• Semi-blind intercomparison of UV-Vis (MAX-)DOAS sensors, with external referee:

  • Assess consistency of instruments (following FRM principles)

  • Certification of (new) instruments contributing to ACTRIS/NDACC

• Provide training on various aspects of instrument operation, calibration, QA/QC of data

• Motivate R&D on new products developments, harmonization of retrieval strategies, etc

• Target species:

  • main: NO₂, O₃

  • secondary: HCHO, CHOCHO and aerosols

  • other: HONO, BrO, H₂O

• Products to intercompare:

  • slant columns from direct-sun and sky (MAX-DOAS) measurements

  • Vertical columns

  • Partial columns & profiles