Difference between revisions of "Sky temperature maps"

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A typical header for the data extension of an intensity only map is:
 
A typical header for the data extension of an intensity only map is:
  
−
  XTENSION= 'BINTABLE'          / binary table extension                       
+
;-----------------------------------------------------------------------------
−
  BITPIX  =                    8 / 8-bit bytes                                   
+
; EXTENSION 1: FREQ-MAP
−
  NAXIS  =                    2 / 2-dimensional binary table                    
+
; - Header
−
  NAXIS1  =                   12 / width of table in bytes                      
+
;-----------------------------------------------------------------------------
−
  NAXIS2  =             50331648 / number of rows in table                       
+
  XTENSION= 'BINTABLE'          /Written by IDL:  Fri Nov 30 15:13:55 2012     
−
  PCOUNT  =                    0 / size of special data area                     
+
  BITPIX  =                    8 /                                              
−
  GCOUNT  =                    1 / one data group (required keyword)             
+
  NAXIS  =                    2 /Binary table                                  
−
  TFIELDS =                    3 / number of fields in each row                 
+
  NAXIS1  =           603979776 /Number of bytes per row                       
−
  TTYPE1  = 'I_Stokes'          / label for field  1                           
+
  NAXIS2  =                   1 /Number of rows                                
−
  TFORM1 = '1E8    '          / data format of field: 4-byte REAL             
+
  PCOUNT  =                    0 /Random parameter count                         
−
  TUNIT1 = 'K_CMB  '          / physical unit of field                       
+
  GCOUNT  =                    1 /Group count                                   
−
  TTYPE2 = 'Hits    '           / label for field  2                           
+
  TFIELDS =                    3 /Number of columns                             
−
  TFORM2  = '1J      '           / data format of field: 4-byte INTEGER         
+
COMMENT                                                                       
−
  TUNIT2 = 'none    '           / physical unit of field                       
+
COMMENT  *** End of mandatory fields ***                                       
−
  TTYPE3 = 'II_cov  '          / label for field  3                           
+
COMMENT                                                                       
−
  TFORM3 = '1E8    '          / data format of field: 4-byte REAL             
+
COMMENT                                                                       
−
  TUNIT3  = '(K_CMB)^2'          / physical unit of field                       
+
COMMENT  *** Column names ***                                                 
−
  EXTNAME = 'CH-MAP '          / name of this binary table extension           
+
COMMENT                                                                       
−
FREQ    = '857    '                                                           
+
  TTYPE1  = 'I_STOKES'          /                                              
−
  PIXTYPE = 'HEALPIX '                                                           
+
  TTYPE2 = 'HITS    '          /                                              
−
COORDSYS= 'GALACTIC'                                                          
+
  TTYPE3 = 'II_COV  '          /                                              
−
  ORDERING= 'NESTED  '                                                          
+
COMMENT                                                                       
−
FILENAME= 'HFI_857-2_2048_20120210_nominal.fits'                               
+
COMMENT  *** Column formats ***                                               
−
  NSIDE  =                2048                                                
+
COMMENT                                                                       
−
CHANNEL = '857-2  '                                                           
+
  TFORM1 = '50331648E'         /                                              
−
  FIRSTPIX=                    0                                                
+
  TFORM2  = '50331648E'         /                                              
−
  LASTPIX =            50331647                                                
+
  TFORM3 = '50331648E'         /                                              
−
  EXTVER  = '1      '                                                          
+
COMMENT                                                                       
−
  PROCVER = 'v50    '                                                          
+
COMMENT  *** Column units ***                                                 
−
  BAD_DATA= '-1.63750E+30'                                                         
+
COMMENT                                                                       
−
  COMMENT = 'Rel DR4 '                                                           
+
  TUNIT1 = 'K_CMB  '          /                                              
−
  END
+
  TUNIT2 = '       '          /                                              
 +
  TUNIT3  = 'K_CMB  '          /                                               
 +
COMMENT                                                                       
 +
COMMENT  *** Planck params ***                                                 
 +
COMMENT                                                                       
 +
UNITCONV=              0.00000 / (MJy/sr)/K_cmb unit conv. factor             
 +
  EXTNAME = 'FREQ-MAP'          /                                              
 +
  COORSYS = 'GALACTIC'           / Coordinate system                             
 +
  ORDERING= 'NESTED  '           / Healpix ordering                             
 +
  NSIDE  =                2048 / Healpix Nside                                 
 +
  FIRSTPIX=                    0 /                                               
 +
  LASTPIX =            50331647 /                                               
 +
  FILENAME= 'HFI_SkyMap_100_2048_R1.00_nominal.fits' / FITS filename             
 +
  FILEDATE= '2012-11-30 15:13'   / File creation date                           
 +
  BAD_DATA=         -1.63750E+30 / bad pixel value                               
 +
PROCVER = 'DX9-delta'         / Product version                               
 +
COMMENT                                                                       
 +
COMMENT ------------------------------------------------------------------------
 +
COMMENT Full channel frequency map for nominal mission                         
 +
COMMENT ------------------------------------------------------------------------
 +
COMMENT HFI-DMC objects:                                                        
 +
  COMMENT in-group: MAP_DX9_2048_GALACTIC_0240_27008/                           
 +
COMMENT Creation date  - object name                                           
 +
COMMENT 12-05-29 13:38 - 100GHz_W_TauDeconv_nominal_I                         
 +
COMMENT 12-05-29 13:38 - 100GHz_W_TauDeconv_nominal_H                         
 +
COMMENT 12-05-29 13:38 - 100GHz_W_TauDeconv_nominal_II                         
 +
COMMENT ------------------------------------------------------------------------
 +
  END                                                                            
  
−
and for a polarized frequency map:
 
−
 
−
XTENSION= 'BINTABLE'          / binary table extension                       
 
−
BITPIX  =                    8 / 8-bit bytes                                   
 
−
NAXIS  =                    2 / 2-dimensional binary table                   
 
−
NAXIS1  =                  40 / width of table in bytes                       
 
−
NAXIS2  =            50331648 / number of rows in table                       
 
−
PCOUNT  =                    0 / size of special data area                     
 
−
GCOUNT  =                    1 / one data group (required keyword)             
 
−
TFIELDS =                  10 / number of fields in each row                 
 
−
TTYPE1  = 'I_Stokes'          / label for field  1                           
 
−
TFORM1  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT1  = 'K_CMB  '          / physical unit of field                       
 
−
TTYPE2  = 'Q_Stokes'          / label for field  2                           
 
−
TFORM2  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT2  = 'K_CMB  '          / physical unit of field                       
 
−
TTYPE3  = 'U_Stokes'          / label for field  3                           
 
−
TFORM3  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT3  = 'K_CMB  '          / physical unit of field                       
 
−
TTYPE4  = 'Hits    '          / label for field  4                           
 
−
TFORM4  = '1J      '          / data format of field: 4-byte INTEGER         
 
−
TUNIT4  = 'none    '          / physical unit of field                       
 
−
TTYPE5  = 'II_cov  '          / label for field  5                           
 
−
TFORM5  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT5  = '(K_CMB)^2'          / physical unit of field                       
 
−
TTYPE6  = 'IQ_cov  '          / label for field  6                           
 
−
TFORM6  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT6  = '(K_CMB)^2'          / physical unit of field                       
 
−
TTYPE7  = 'IU_cov  '          / label for field  7                           
 
−
TFORM7  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT7  = '(K_CMB)^2'          / physical unit of field                       
 
−
TTYPE8  = 'QQ_cov  '          / label for field  8                           
 
−
TFORM8  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT8  = '(K_CMB)^2'          / physical unit of field                       
 
−
TTYPE9  = 'QU_cov  '          / label for field  9                           
 
−
TFORM9  = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT9  = '(K_CMB)^2'          / physical unit of field                       
 
−
TTYPE10 = 'UU_cov  '          / label for field  10                           
 
−
TFORM10 = '1E8    '          / data format of field: 4-byte REAL             
 
−
TUNIT10 = '(K_CMB)^2'          / physical unit of field                       
 
−
EXTNAME = 'FR-MAP  '          / name of this binary table extension           
 
−
FREQ    = '217    '                                                           
 
−
PIXTYPE = 'HEALPIX '                                                           
 
−
COORDSYS= 'GALACTIC'                                                           
 
−
ORDERING= 'NESTED  '                                                           
 
−
FILENAME= 'HFI_217_2048_20120210_nominal.fits'                                 
 
−
NSIDE  =                2048                                                 
 
−
FIRSTPIX=                    0                                                 
 
−
LASTPIX =            50331647                                                 
 
−
EXTVER  = '1      '                                                           
 
−
PROCVER = 'v50    '                                                           
 
−
BAD_DATA= '-1.63750E+30'                                                       
 
−
COMMENT = 'Rel DR4 '                                                           
 
−
END
 
  
 
[[Category:Mission science products]]
 
[[Category:Mission science products]]

Revision as of 12:56, 3 December 2012

Introduction[edit]

Frequency maps are produced by combining appropriately the data of several detectors over some period of the mission. They may be intensity only or polarized, meaning that they will consist of a set of three maps of I, Q, and U. These will be accompanied by a hit-count map and by a set of variance maps. All maps are in Healpix format, with Nside of 2048 for HFI and of 1024 for LFI, in Galactic coordinates, and Nested ordering. The maps are packaged into a single BINTABLE extension; the structure of the FITS file is given in the FITS file structure section below.

The FITS filenames are of the form {H|L}FI_fff_nnnn_yyyymmdd_{type}_{mission}.fits, where fff are three digits to indicate the Planck frequency band, and nnnn is the Healpix Nside of the map, the optional type indicates the subset of input data used, and mission indicates the coverage period, i.e., full, nominal, or survey_n (TBC; an alternative of the type {H|L}FI_fff_{type}_{mission}_Rn.mm.fits is being considered, where Rn.mm is the release number). A full list of products, by their names, is given in the List of products below.

HFI processing[edit]

The cleaned TOIs of each detector (calibrated in Watts) with their associated flags (flagged samples and anomalous rings) are first used to build Healpix rings, each ring containing the combined data of one pointing period. These are then calibrated in brightness, cleaned of the dipole signals, and projected onto Healpix maps as explained in the following sections.

Gains are initially determined for each pointing period. These estimates are systematically biased by Galactic foregrounds. These gains are averaged over a time interval in the first survey where the Solar dipole amplitude is large enough to reduce these bias. For 100 to 217 GHz, evidence of apparent gain variations of order 1 to 2% over a few tens to thousands of pointing periods led us to adopt a more sophisticated approach, where we determined relative gains for each pointing period, smoothed with a 50 pointing period width.

At the higher frequencies, 545 and 857 GHz, calibration is map-based; a constant gain is determined by fitting HFI data onto FIRAS data, together with a zero-point (as FIRAS is absolutely calibrated). These zero point are applied for all frequencies to set them at the same scale.

A destriping approach is used, where noise is modelled as the sum of a white noise component and a constant, aka offset, per pointing period which represent the low frequency 1/f noise. After subtracting these offsets, calibrated data are projected onto Healpix maps, with the data of each bolometer weighted by a factor of 1/NET of that bolometer. Maps are build after a simple classical dipole removal based on WMAP measurements.

Together with signal maps, hit count and variance maps are also produced. The hit maps give the (integer) number of valid TOI-level samples that contribute to the signal of each pixel. All valid samples are counted in the same way, i.e., there is no weighting factor applied. The variance maps project the white noise estimate, provided by the NETs, in the sky domain. They give the covariance between the Stokes parameters I,Q andU inside each pixels, whenever polarization is reconstructed.

LFI processing[edit]

TBW

Types of maps[edit]

Full channel maps[edit]

Full channel maps are built using all the valid detectors of a frequency channel and cover the full mission (or the nominal mission for the 1st release). For HFI, the 143-8 and 545-3 bolometers are rejected entirely as they are seriously affected by RTS noise.

Single survey maps[edit]

Single survey maps are built using all valid detectors of a frequency channel, but cover separately the different sky surveys. The single sky surveys are defined in terms of the direction of the satellite's spin axis: the first survey covers from the beginning of the science observations (the First Light Survey) to the time when the spin axis has rotated by 180 degrees (to the nearest pointing period), the following ones covers from 180 to 360, and so on. In the case of the nominal mission, the process stops at the third survey, which is incomplete. In the case of the full mission the 4th survey was interrupted shortly before completing the 180 degree rotation (see LINK), in order to begin observing with a different scanning law. The HFI mission ended slightly before the natural end of the 5th survey, the LFI mission continued to the XXX survey. The coverage of each of these periods in terms of ring number, pointingID, and OD, is given in the table below. Note that the OD numbers are only to indicate during which OD the period boundary occurs.

Missions and sky survey coverage periods
Name Ini_OD Ini_Ring Ini_ptgID End_OD End_ring End_ptgID
Nominal 91 240 00004200 807 14724 04243900
HFI-Full 91 240 00004200 563 27008 06344800
LFI-Full 91 240 00004200 TBD TBD TBD
SCAN1 91 240 00004200 270 5720 01059820
SCAN2 270 5721 01059830 456 11194 02114520
SCAN3 456 11195 02114530 636 16691 03193660
SCAN4 636 16692 03193670 807 21720 04243990
SCAN5 807 21721 95000020 974 27008 06344800


Detector-set maps[edit]

There are no detset maps in the first release.

This section will serve for later releases.

Detector-set (detset) maps are built for the full (or nominal) mission using a minimal set of detectors. This concept is applicable to polarization maps, which are built using two PSB pairs at the proper orientations. The HFI polarized channels are designed to provide two detsets (or quads) each, namely:

HFI detector sets or quads
100–ds1: 100-1a,100-1b,100-4a,100-4b 100–ds2: 100-2a,100-2b,100-3a,100-3b
143–ds1: 143-1a,143-1b,143-3a,143-3b 143–ds2: 143-2a,143-2b,143-4a,143-4b
217–ds1: 217-5a,217-5b,217-7a,217-7b 217–ds2: 217-6a,217-6b,217-8a,217-8b
353–ds1: 353-5a,353-5b,353-3a,353-3b 353–ds2: 353-6a,353-6b,353-4a,353-4b

Some maps built using a set of a single detector are also provided, and are described in Single detector maps

The LFI Detector-set maps are built using pairs of horns in the same scanning row, namely:

LFI Couple Horn sets
18_23: 18M,18S,23M,23S
19_22: 19M,19S,22M,22S
20_21: 20M,20S,21M,21S
24: 24M,24S
25_26: 25M,25S,26M,26S


Half-ring maps[edit]

Half-ring maps are built using only the first or the second half of the stable pointing period data. There are thus two half-ring maps per frequency channel named ringhalf_1 and ringhalf_2 respectively. These maps are built for characterization purposes in order to perform null tests.


List of products[edit]

First release[edit]

For the first release, all maps will be Intensity-only

Full channel maps 
LFI_030_2048_yyyymmdd_nominal.fits
LFI_044_2048_yyyymmdd_nominal.fits
LFI_070_2048_yyyymmdd_nominal.fits
HFI_100_2048_yyyymmdd_nominal.fits
HFI_143_2048_yyyymmdd_nominal.fits
HFI_217_2048_yyyymmdd_nominal.fits
HFI_353_2048_yyyymmdd_nominal.fits
HFI_545_2048_yyyymmdd_nominal.fits
HFI_857_2048_yyyymmdd_nominal.fits
Single survey maps 
LFI_030_2048_yyyymmdd_survey_1.fits
LFI_030_2048_yyyymmdd_survey_2.fits
LFI_030_2048_yyyymmdd_survey_3.fits
LFI_044_2048_yyyymmdd_survey_1.fits
LFI_044_2048_yyyymmdd_survey_2.fits
LFI_044_2048_yyyymmdd_survey_3.fits
LFI_070_2048_yyyymmdd_survey_1.fits
LFI_070_2048_yyyymmdd_survey_2.fits
LFI_070_2048_yyyymmdd_survey_3.fits
HFI_100_2048_yyyymmdd_survey_1.fits
HFI_100_2048_yyyymmdd_survey_2.fits
HFI_100_2048_yyyymmdd_survey_3.fits
HFI_143_2048_yyyymmdd_survey_1.fits
HFI_143_2048_yyyymmdd_survey_2.fits
HFI_143_2048_yyyymmdd_survey_3.fits
HFI_217_2048_yyyymmdd_survey_1.fits
HFI_217_2048_yyyymmdd_survey_2.fits
HFI_217_2048_yyyymmdd_survey_3.fits
HFI_353_2048_yyyymmdd_survey_1.fits
HFI_353_2048_yyyymmdd_survey_2.fits
HFI_353_2048_yyyymmdd_survey_3.fits
HFI_545_2048_yyyymmdd_survey_1.fits
HFI_545_2048_yyyymmdd_survey_2.fits
HFI_545_2048_yyyymmdd_survey_3.fits
HFI_857_2048_yyyymmdd_survey_1.fits
HFI_857_2048_yyyymmdd_survey_2.fits
HFI_857_2048_yyyymmdd_survey_3.fits
Half-ring maps 
LFI_030_2048_yyyymmdd_ringhalf_1_nominal.fits
LFI_030_2048_yyyymmdd_ringhalf_2_nominal.fits
LFI_044_2048_yyyymmdd_ringhalf_1_nominal.fits
LFI_044_2048_yyyymmdd_ringhalf_2_nominal.fits
LFI_070_2048_yyyymmdd_ringhalf_1_nominal.fits
LFI_070_2048_yyyymmdd_ringhalf_2_nominal.fits
HFI_100_2048_yyyymmdd_ringhalf_1_nominal.fits
HFI_100_2048_yyyymmdd_ringhalf_2_nominal.fits
HFI_143_2048_yyyymmdd_ringhalf_1_nominal.fits
HFI_143_2048_yyyymmdd_ringhalf_2_nominal.fits
HFI_217_2048_yyyymmdd_ringhalf_1_nominal.fits
HFI_217_2048_yyyymmdd_ringhalf_2_nominal.fits
HFI_353_2048_yyyymmdd_ringhalf_1_nominal.fits
HFI_353_2048_yyyymmdd_ringhalf_2_nominal.fits
HFI_545_2048_yyyymmdd_ringhalf_1_nominal.fits
HFI_545_2048_yyyymmdd_ringhalf_2_nominal.fits
HFI_857_2048_yyyymmdd_ringhalf_1_nominal.fits
HFI_857_2048_yyyymmdd_ringhalf_2_nominal.fits

Second release[edit]

All the above + TBD, including polarization for the polarized frequency channels.


FITS file structure[edit]

The FITS file will have one of the following structures:


FITS file structure

The exact order of the columns is indicative only, and the details will be given in the keywords. Keywords will also indicate the coordinate system (GALACTIC), the Healpix ordering scheme (NESTED), the units (K_cmb), and of course the detector. Details of the FITS file general structure can be found in the EFDD (ref), and the specifics of certain parameters in ICD-031 (ref)

Header keywords[edit]

A typical header for the data extension of an intensity only map is: 

;-----------------------------------------------------------------------------
; EXTENSION 1: FREQ-MAP
; - Header
;-----------------------------------------------------------------------------
XTENSION= 'BINTABLE'           /Written by IDL:  Fri Nov 30 15:13:55 2012       
BITPIX  =                    8 /                                                
NAXIS   =                    2 /Binary table                                    
NAXIS1  =            603979776 /Number of bytes per row                         
NAXIS2  =                    1 /Number of rows                                  
PCOUNT  =                    0 /Random parameter count                          
GCOUNT  =                    1 /Group count                                     
TFIELDS =                    3 /Number of columns                               
COMMENT                                                                         
COMMENT  *** End of mandatory fields ***                                        
COMMENT                                                                         
COMMENT                                                                         
COMMENT  *** Column names ***                                                   
COMMENT                                                                         
TTYPE1  = 'I_STOKES'           /                                                
TTYPE2  = 'HITS    '           /                                                
TTYPE3  = 'II_COV  '           /                                                
COMMENT                                                                         
COMMENT  *** Column formats ***                                                 
COMMENT                                                                         
TFORM1  = '50331648E'          /                                                
TFORM2  = '50331648E'          /                                                
TFORM3  = '50331648E'          /                                                
COMMENT                                                                         
COMMENT  *** Column units ***                                                   
COMMENT                                                                         
TUNIT1  = 'K_CMB   '           /                                                
TUNIT2  = '        '           /                                                
TUNIT3  = 'K_CMB   '           /                                                
COMMENT                                                                         
COMMENT  *** Planck params ***                                                  
COMMENT                                                                         
UNITCONV=              0.00000 / (MJy/sr)/K_cmb unit conv. factor               
EXTNAME = 'FREQ-MAP'           /                                                
COORSYS = 'GALACTIC'           / Coordinate system                              
ORDERING= 'NESTED  '           / Healpix ordering                               
NSIDE   =                 2048 / Healpix Nside                                  
FIRSTPIX=                    0 /                                                
LASTPIX =             50331647 /                                                
FILENAME= 'HFI_SkyMap_100_2048_R1.00_nominal.fits' / FITS filename              
FILEDATE= '2012-11-30 15:13'   / File creation date                             
BAD_DATA=         -1.63750E+30 / bad pixel value                                
PROCVER = 'DX9-delta'          / Product version                                
COMMENT                                                                         
COMMENT ------------------------------------------------------------------------
COMMENT Full channel frequency map for nominal mission                          
COMMENT ------------------------------------------------------------------------
COMMENT HFI-DMC objects:                                                        
COMMENT in-group: MAP_DX9_2048_GALACTIC_0240_27008/                             
COMMENT Creation date  - object name                                            
COMMENT 12-05-29 13:38 - 100GHz_W_TauDeconv_nominal_I                           
COMMENT 12-05-29 13:38 - 100GHz_W_TauDeconv_nominal_H                           
COMMENT 12-05-29 13:38 - 100GHz_W_TauDeconv_nominal_II                          
COMMENT ------------------------------------------------------------------------
END

(Planck) High Frequency Instrument

(Planck) Low Frequency Instrument

Flexible Image Transfer Specification

To be confirmed

Noise Equivalent Temperature

random telegraphic signal

Operation Day definition is geometric visibility driven as it runs from the start of a DTCP (satellite Acquisition Of Signal) to the start of the next DTCP. Given the different ground stations and spacecraft will takes which station for how long, the OD duration varies but it is basically once a day.

To be defined / determined

Interface Control Document

Cosmic Microwave background

Data Management Component, the databases used at the HFI and LFI DPCs

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