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The Explanatory Supplement is a reference text accompanying the public data products which result from the European Space Agency’s Planck mission, and includes descriptions of all the products available via the Planck Legacy Archive. The Explanatory Supplement has been produced by the Planck Collaboration.

There are have been four major data releases of Planck products:

• PR1 in 2013 (all files are identified by the label *.R1.??) ;
• PR2 in 2015 (all files are identified by the label *.R2.??) ;
• PR3 in 2018 (all files are identified by the label *.R3.??) ;
• PR4 (NPIPE) in 2020 (all files are identified by the label *.R4.??) .

In addition, the so-called "Planck Legacy Release" is a combination of PR1+PR2+PR3 products tha thave been tagged as "Legacy" and are shown by default the PLA.

This Explanatory Supplement accompanies the Planck 2018 release, however, the descriptions of the 2013, 2015 and 2020 products can be found at the end of each section under the heading Other Releases and appear under different background colors (white for 2018, salmon for 2015 and green for 2013).

Also note that not all the products issued in 2015 have been updated in the 2018 or 2020 release, this is one of the reasons for tagging a "Legacy" release.

The Index of the Explanatory Supplement is listed below; the Index and individual section headings can also be accessed directly via the menu bar at the left of this page.

1. Introduction
   1. The Planck mission
   2. The spacecraft
   3. Ground segment and Early operations
   4. Survey scanning and Routine operations
   5. Questions and answers
2. The instruments
   1. HFI design, qualification, and performance
      1. Cryogenics
      2. HFI cold optics and spectral response
      3. Detection chain
      4. Operations
      5. Performance summary
      6. Annexes
   2. LFI design, qualification, and performance
      1. Instrument description
      2. Ground tests
      3. In-flight calibration
      4. Performance summary
      5. Systematic effects
      6. Sorption cooler
      7. Annexes
3. Data processing
   1. HFI data processing
      1. Pre-processing
      2. TOI processing
      3. Beams
      4. Spectral response
      5. Systematic effects
      6. Mapmaking
      7. Internal overall validation
      8. Summary of HFI data characteristics
      9. HFI simulations
   2. LFI data processing
      1. Pre-processing
      2. TOI processing
      3. Beams
      4. Galactic stray light removal
      5. Mapmaking
      6. Systematic effects uncertainties
      7. Internal overall validation
      8. Summary of LFI data characteristics
   3. HFI/LFI joint data processing
      1. Detector pointing
      2. Compact source catalogues
      3. Astrophysical component separation
      4. CMB power spectra and Planck likelihood code
      5. NPIPE data processing pipeline
4. Planck Legacy Archive: mission products
   1. Timelines and Rings
      1. Timelines
      2. HEALPix rings
   2. Maps
      1. Frequency maps in Temperature and Polarization
      2. CMB maps
      3. Foreground maps
         1. Overview
         2. Commander-derived astrophysical foreground maps
         3. SMICA-derived astrophysical foreground maps
         4. GNILC thermal dust maps
      4. Correction maps
      5. Masks
      6. Simulation data
      7. External maps
         1. WMAP
         2. Haslam
         3. IRIS
         4. WISE
         5. IRAM - Crab nebula
      8. Dates of observations
   3. Catalogues
      1. PCCS
      2. PSZ
      3. PGCC
      4. PHZ
   4. Cosmology
      1. CMB spectrum and likelihood code
      2. Cosmological parameters and MC chains
      3. Lensing
   5. Beams
      1. Scanning beams
      2. Optical beams
      3. Effective beams
      4. Beam window functions
   6. Instrument model
   7. Planet-related data
   8. Software utilities
      1. Unit conversion and colour correction
      2. SMICA propagation code
5. Planck value-added tools
6. Operational data
   1. Survey history data
   2. Satellite history data
   3. Planck operational state history
   4. Space radiation environment monitor
7. Appendix
   1. Glossary
   2. List of acronyms