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Metis data format & availability

R. Susino & the Metis team

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Aditya-L1 & Metis Meeting – February 25th, 2025

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Data types & on-board processing

Visible-light channel

    • polarised-brightness (pB) mode → sequences of 4 polarised images (min. 1 minute cadence)
      • polarised images, polarised and total brightness, polarisation angle, Stokes parameters
    • total-brightness (tB) mode → switch of polarisation at mid. integration (min. 20 s cadence)
      • single total-brightness image
    • fixed-polarisation (FP) mode (min. 1 s cadence)
      • single polarimetric image

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UV channel

    • analogue-mode → single HI Lyman-α image

135° pol.

90° pol.

pol. angle

0° pol.

45° pol.

pB

HI Lyα

tB

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Data types & on-board processing

On-board processing

    • frame average
    • binning, masking
    • compression (lossless, lossy)
    • cosmic-ray/SEP correction

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Secondary data products

    • light curves (for each pB sequence)
    • cosmic-ray/SEP correction maps (twice per day)

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Data flow

Solar Orbiter Archive

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Metis pipeline

Mission Operation Centre

L2

Telemetry

Data

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On-ground processing and calibration

Level 0 (L0)

    • uncalibrated data (units of DN) obtained from telemetry packets, that are uncompressed and formatted in standard FITS format
    • metadata contain only the information that is available from the telemetry packet headers

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Level 1 (L1)

    • uncalibrated data (units of DN)
    • metadata contain extra engineering data from housekeeping telemetry
    • all the available orbital and attitude information is used and coordinates expressed in scientific coordinate systems (WCS)

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On-ground processing and calibration

Level 2 (L2)

    • calibrated data (physical units)
    • standard operations:
      • detector bias/dark current correction
      • flat-field correction
      • optical vignetting correction
      • exposure normalisation
      • radiometric calibration
      • demodulation (applied only to polarimetric acquisitions)
    • the most up-to-date calibration is always applied

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On-ground processing and calibration

Level 2 (L2)

    • calibrated data (physical units)
    • standard operations:
      • detector bias/dark current correction
      • flat-field correction
      • optical vignetting correction
      • exposure normalisation
      • radiometric calibration
      • demodulation (applied only to polarimetric acquisitions)
    • the most up-to-date calibration is always applied

Calibration papers

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De Leo et al. (2023) A&A 676, A45 - VL

Liberatore et al. (2023) A&A 672, A14 - VL

Uslenghi et al. (2024) SPIE 13103, 1310324 - UV

De Leo et al. (2024) A&A in press - UV

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On-ground processing and calibration

Level 3 (L3) → science-grade data derived from L2 data:

    • data obtained after scientific analysis, e.g., electron-density maps, solar-wind outflow velocity maps
    • images, movies, Carrington maps → JP2000 (image + header) and PNG images available soon

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L2 FITS structure

  • Quality matrix
    • image mask flagging:
      • saturated/bad pixels (NaN)
      • unreliable pixel values (0)
      • good pixels (1)
  • Error matrix
    • uncertainty map derived from measured counts through error propagation → under assessment

Main

header

Image*

Quality

matrix

Error

matrix

Stokes Q

Stokes U

* VL pB tB, pol. angle, or Stokes I or UV Lyα intensity

FITS file

FITS extensions

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Data availability

Nominal-phase L2 data

    • publicly available through the Solar Orbiter Archive (SOAR) at https://soar.esac.esa.int/soar/ (~ 90 days after download) → available up to March 2024

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L2 data not yet available on the SOAR, L0, L1, or cruise-phase data

    • available upon request, please write to metis@inaf.it

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https://soar.esac.esa.int/soar/

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https://soar.esac.esa.int/soar/

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http://metis.oato.inaf.it

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Title Text

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Title Text

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How to look into Metis data?

  • With any tool that can handle FITS files...
  • Recommended: iCID (IDL Coronal Images Display, developed and maintained by Silvio G.) or the python version pyCID (developed and maintained by Aleksandr B.)

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JHelioviewer

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JHelioviewer

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JHelioviewer

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Reference documents and useful links