Sky temperature maps
Introduction[edit]
Sky maps are produced by combining appropriately the data of all working detectors in a frequency channel over some period of the mission. They give the best estimate of the signal from the sky (unpolarised) after removal, as far as possible, of known systematic effects and of the dipole signals induced by the motion of the solar system in the CMB and of the Planck satellite in the solar system. In particular, they include the Zodiacal light emission (Zodi for short) and also the scattering from the far-side lobes of the beams (FSL). More on this below.
Sky maps are provided for the nominal Planck mission and for the first two single surveys, the third one being covered only for a small part during the nominal mission (REF). AMo: There is a table with table below that defines these coverage periods, but I believe that information should be in an earlier section that describes the mission and the events that interrupted it, the planet passages, the pointing, issues relating to timing, etc. That section should define a pointing period, and operational day, etc. There is some of that info in the HFI pre-processing section, but that may not be the best place for it.For characterization purposes, are also provided maps covering the nominal survey but using only half of the available data. These are the ringhalf_{1|2} maps, which are built using the first and second half of the stable pointing part of the data in each pointing period.
| Name | Ini_OD | Ini_Ring | Ini_ptgID | End_OD | End_ring | End_ptgID |
|---|---|---|---|---|---|---|
| Nominal | 91 | 240 | 00004200 | 563 | 14724 | 03180200 |
| HFI-Full | 91 | 240 | 00004200 | 993 | 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 | 04243900 |
| SCAN5 | 807 | 21721 | 95000020 | 993 | 27008 | 06344800 |
| SCAN6 | 993 | ---- | 06344810 | 993 | ---- | TBD |
All sky maps are in Healpix format, with Nside of 2048 for HFI and of 1024 for LFI, in Galactic coordinates, and Nested ordering. The signal is given in units of Kcmb for 33-353 GHz, and of MJy/sr (for a constant $\nu F_\nu$ energy distribution ) for 545 and 857 GHz. Each sky map is packaged into a BINTABLE extension of a FITS file together with a hit-count map (or hit map, for short) and a variance map, and additional information is given in the FITS file header. 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_SkyMap_fff_nnnn_R1.nn_{type}_{coverage}_{type}.fits, where fff are three digits to indicate the Planck frequency band, and nnnn is the Healpix Nside of the map, coverage indicates which part of the mission is covered, and the optional type indicates the subset of input data used. A full list of products, by their names, is given in the List of products below.
HFI processing[edit]
The mapmaking pipeline is described in detail in the Map-making section, and a brief summary is given here for convenience.
The cleaned TOIs of signal of each detector, together with their flags, and the TOIs of pointing (quaternions), are the inputs to the mapmaking step. The input signal TOIs are calibrated in Watt, and their associated flags are used to samples or full rings to discard. Are discarded periods of unstable pointing and pointing maneuvers in general, glitched data, transits over bright planets (and some asteroids TBC) (since they move, the hole is covered during another sky survey), and some full rings are discarded if their noise properties differ significantly from the nominal value and the few rings of duration longer than 90 min, since the pointing is not sufficiently stable over such long periods (details in Discarded rings section). The TOIs are first used to build Healpix rings, each ring containing the combined data of one pointing period using the nearest grid point method (NGP). These are then calibrated in brightness, cleaned of the dipole signals, and projected onto Healpix maps as explained in the following sections. Need to add POINTING DETAILS
The cleaned TOIs are expressed in Watts from the sky absorbed by the bolometer and must be calibrated in astrophysical units. At 100-353 GHz, the flux calibration gains are determined for each pointing period (or ring) from the solar-motion dipole after removal of the small dipole induced by the motion of the Planck satellite in the solar system. The solar-motion dipole from WMAP (REF) is used for this purpose. This gain by ring is then smoothed with a window of width 50 rings, which reveals an apparent variation of ~1-2% on a scale of 100s to 1000s of rings for the 100-217 GHz channels, and is applied to the Watt data. At 353GHz, where the solar motion dipole is weaker compared to the signal, no gain variation is detected, and the same fixed gain is applied to all rings. At 545 and 857 GHz the gain is determined from the observation of Uranus and Neptune (Jupiter is not used because its brightness produced some non-linearity in the bolometer response) and comparison to recent models (REF) made explicitly for this mission. A single gain is applied to all rings at these frequencies.
Prior to projecting the Healpix rings (HPRs) onto a map, a destriping approach is used to remove low-frequency noise. The noise is modelled as the sum of a white noise component and a constant, or offset, per pointing period which represents the low frequency 1/f noise. The offsets are determined by minimizing the differences between HPRs at their crossings. 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.
These maps provide the main mission products. A second, reduced, set of maps, cleaned of the Zodiacal emission of the FSL leakage is also produced for the nominal mission and the two single surveys, but not for the half-rings. For this purpose, the the Zodiacal emission and the FSL contamination, which are not fixed on the sky, are modeled separately at HPR-level, and subtracted from the signal HPR before projecting them onto the maps.
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.
LFI processing[edit]
LFI processing is covered in Sect. 4.5
Selected images[edit]
Insert here some images:
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.
Caveats and known issues[edit]
The Zodiacal light and the Far-Side Lobes[edit]
Insert here how these are seen in the differences of the single survey maps
Artifacts near caustics of the scanning strategy[edit]
TBW if still an issue??
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]
A comment from E. Keihänen:
Here is a list of things that should go into this section:
- Insert a table of maps delivered
-file name
-radiometers included
-PID/OD range
-resolution
(-polarization included or not)
-sky coverage
-baseline length
(-reference to input toi objects)
- Explain the format of the files, what is in what column, in what units.
- Information common for all LFImaps
-LFI maps were constructed with the Madam map-making code (version 3.7.4).
-Maps are in Healpix format, in nested pixeling scheme, in K_cmb units, and in galactic coordinate system.
-Unobserved pixels are marked by the special value -1.6375e30.
EK's comment ends
The list of products containing sky maps are given below, grouped by type
Outstanding: link to archive objects / LFI to fill in their products
- Full channel maps
LFI maps …. HFI_SkyMap_100_2048_R1.nn_nominal.fits HFI_SkyMap_143_2048_R1.nn_nominal.fits HFI_SkyMap_217_2048_R1.nn_nominal.fits HFI_SkyMap_353_2048_R1.nn_nominal.fits HFI_SkyMap_545_2048_R1.nn_nominal.fits HFI_SkyMap_857_2048_R1.nn_nominal.fits
- Single survey maps
LFI maps …. HFI_SkyMap_100_2048_R1.nn_survey_1.fits HFI_SkyMap_143_2048_R1.nn_survey_1.fits HFI_SkyMap_217_2048_R1.nn_survey_1.fits HFI_SkyMap_353_2048_R1.nn_survey_1.fits HFI_SkyMap_545_2048_R1.nn_survey_1.fits HFI_SkyMap_857_2048_R1.nn_survey_1.fits HFI_SkyMap_100_2048_R1.nn_survey_2.fits HFI_SkyMap_143_2048_R1.nn_survey_2.fits HFI_SkyMap_217_2048_R1.nn_survey_2.fits HFI_SkyMap_353_2048_R1.nn_survey_2.fits HFI_SkyMap_545_2048_R1.nn_survey_2.fits HFI_SkyMap_857_2048_R1.nn_survey_2.fits
- Half-ring maps
LFI maps …. HFI_SkyMap_100_2048_R1.nn_nominal_ringhalf_1.fits HFI_SkyMap_143_2048_R1.nn_nominal_ringhalf_1.fits HFI_SkyMap_217_2048_R1.nn_nominal_ringhalf_1.fits HFI_SkyMap_353_2048_R1.nn_nominal_ringhalf_1.fits HFI_SkyMap_545_2048_R1.nn_nominal_ringhalf_1.fits HFI_SkyMap_857_2048_R1.nn_nominal_ringhalf_1.fits HFI_SkyMap_100_2048_R1.nn_nominal_ringhalf_2.fits HFI_SkyMap_143_2048_R1.nn_nominal_ringhalf_2.fits HFI_SkyMap_217_2048_R1.nn_nominal_ringhalf_2.fits HFI_SkyMap_353_2048_R1.nn_nominal_ringhalf_2.fits HFI_SkyMap_545_2048_R1.nn_nominal_ringhalf_2.fits HFI_SkyMap_857_2048_R1.nn_nominal_ringhalf_2.fits
- Zodi and Far-side-lobes corrected maps
HFI_SkyMap_100_2048_R1.nn_nominal_ZodiCorrected.fits HFI_SkyMap_143_2048_R1.nn_nominal_ZodiCorrected.fits HFI_SkyMap_217_2048_R1.nn_nominal_ZodiCorrected.fits HFI_SkyMap_353_2048_R1.nn_nominal_ZodiCorrected.fits HFI_SkyMap_545_2048_R1.nn_nominal_ZodiCorrected.fits HFI_SkyMap_857_2048_R1.nn_nominal_ZodiCorrected.fits
HFI_SkyMap_100_2048_R1.nn_survey_1_ZodiCorrected.fits HFI_SkyMap_143_2048_R1.nn_survey_1_ZodiCorrected.fits HFI_SkyMap_217_2048_R1.nn_survey_1_ZodiCorrected.fits HFI_SkyMap_353_2048_R1.nn_survey_1_ZodiCorrected.fits HFI_SkyMap_545_2048_R1.nn_survey_1_ZodiCorrected.fits HFI_SkyMap_857_2048_R1.nn_survey_1_ZodiCorrected.fits HFI_SkyMap_100_2048_R1.nn_survey_2_ZodiCorrected.fits HFI_SkyMap_143_2048_R1.nn_survey_2_ZodiCorrected.fits HFI_SkyMap_217_2048_R1.nn_survey_2_ZodiCorrected.fits HFI_SkyMap_353_2048_R1.nn_survey_2_ZodiCorrected.fits HFI_SkyMap_545_2048_R1.nn_survey_2_ZodiCorrected.fits HFI_SkyMap_857_2048_R1.nn_survey_2_ZodiCorrected.fits
FITS file structure[edit]
The FITS file will have one of the following structures:
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
The header of the Zodiacal light (and FSL) correction maps is:
;----------------------------------------------------------------------------- ; EXTENSION 1: COMP-MAP ; - Header ;----------------------------------------------------------------------------- XTENSION= 'BINTABLE' /Written by IDL: Fri Nov 30 15:29:58 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 = 'CORR_353' / Correction 353 GHz TTYPE2 = 'CORR_545' / Correction 545 GHz TTYPE3 = 'CORR_857' / Correction 857 GHz COMMENT COMMENT *** Column formats *** COMMENT TFORM1 = '50331648E' / TFORM2 = '50331648E' / TFORM3 = '50331648E' / COMMENT COMMENT *** Column units *** COMMENT TUNIT1 = 'K_CMB ' / TUNIT2 = 'MJy/sr[nuI(nu)=cst]' / TUNIT3 = 'MJy/sr[nuI(nu)=cst]' / COMMENT COMMENT *** Planck params *** COMMENT EXTNAME = 'COMP-MAP' / AST-COMP= 'ZODI-FSL' / Component COORSYS = 'GALACTIC' / Coordinate system ORDERING= 'NESTED ' / Healpix ordering NSIDE = 2048 / Healpix Nside FIRSTPIX= 0 / LASTPIX = 50331647 / FILENAME= 'HFI_SkyMap_ZodiCorr_2048_R1.00.fits' / FITS filename FILEDATE= '2012-11-30 15:29' / File creation date BAD_DATA= -1.63750E+30 / bad pixel value PROCVER = 'DX9-delta' / Product version COMMENT COMMENT ------------------------------------------------------------------------ COMMENT This is a map representation of the modelled Zodiacal light and Far Side COMMENT Lobe contributions that have been removed from nominal mission frequency COMMENT maps. See the Explanatory Supplement for details. COMMENT ------------------------------------------------------------------------ COMMENT HFI-DMC objects: COMMENT group uncorr 353: /data/dmc/MISS03/DATA/MAP_v53_noZodi_2048_GALACTIC_024 COMMENT group nozodi 353: /data/dmc/MISS03/DATA/MAP_DX9_2048_GALACTIC_0240_27008 COMMENT group uncorr GAL: /data/dmc/MISS03/DATA/MAP_v53_MJyResca_noZodi_2048_GAL COMMENT group nozodi GAL: /data/dmc/MISS03/DATA/MAP_v53_MJyResca_2048_GALACTIC_0 COMMENT Creation date - object name COMMENT 12-11-26 22:19 - 353GHz_W_TauDeconv_nominal_I COMMENT 12-06-07 21:20 - 353GHz_W_TauDeconv_nominal_I COMMENT 12-11-26 17:54 - 545GHz_W_TauDeconv_nominal_I COMMENT 12-11-24 19:31 - 545GHz_W_TauDeconv_nominal_I COMMENT 12-11-26 17:24 - 857GHz_W_TauDeconv_nominal_I COMMENT 12-11-24 21:09 - 857GHz_W_TauDeconv_nominal_I COMMENT ------------------------------------------------------------------------ END
Cosmic Microwave background
(Planck) High Frequency Instrument
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.
(Planck) Low Frequency Instrument
To be defined / determined
Flexible Image Transfer Specification
To be confirmed
Noise Equivalent Temperature
random telegraphic signal
Interface Control Document
Data Management Component, the databases used at the HFI and LFI DPCs
