Difference between revisions of "Timelines"

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== Semi-raw signal timelines ==
 
 
=== HFI timelines ===
 
 
Originally defined to be the raw (ADU) data demodulated and converted to engineering units (V) via the HFI transfer functions (includes 3-pt filtering?).  But (1) this is not the same demodulation method as used in the TOI prod pipeline, and (2) the ADC correction (or at least one method thereof) implies a modification of the raw data before demodulation.  Thus what the HFI will deliver is not yet decided
 
 
=== LFI timelines ===
 
 
TBW
 
 
== Cleaned and calibrated signal timelines ==
 
 
=== HFI processing ===
 
 
The calibrated timelines are produced by the ''TOIprod'' pipeline (link to wiki; link to paper) which in brief performs the following operations:
 
; demodulation: this is performed around a variable level which is determined from the valid input data (a validity flat from a previous version of the processing is determined for this purpose), and the data are converted to engineering units (V) using known conversion coefficients.
 
; despiking: using the demodulated data converted to V (by the transfer function) the glitches are identified and fitted with templates.  A glitch flag is produced that identifies the strongest part of the glitches, and a timeline of glitch tails is produced from the template fits, and subtracted from the demodulated timeline from step 1.  Finally, the flagged ranges are replaced with data from TBC ''(is this done here, if not where?)''
 
; dark template removal: ''TBW''
 
; conversion to absorbed power: the timeline is converted to watts of absorbed power using the bolometer function.  This includes a non-linearity correction
 
; removal of the 4K cooler lines: ''TBW''
 
at this point a timeline in W and a glitch flag are written to disk
 
; deconvolution by the time transfer function: ''TBW''
 
; jump correction: removes some (relatively rare) jumps in the signal baseline
 
at this point a ''tau-deconvolved'' and ''jump-corrected'' timeline and its associated glitch flag are written to disk. These timelines are later used in the flux calibration and mapmaking stages
 
 
Note that these timelines contain the full sky signal, i.e. including the solar and orbital dipoles and the Zodiacal light. The dipoles are necessary for the flux calibration and are removed by the pipeline at the mapmaking stage. 
 
 
'''Need to discuss dipoles removal and conversion to astrophysical units at the export stage'''
 
 
 
=== LFI processing ===
 
 
TBW
 
 
== Pointing timelines ==
 
 
The pointing is determined starting from the AHF produced by MOC, which gives the direction and orientation of the LOS of a fiducial position in the focal plane at frequencies of 8Hz during stable pointing and 4 Hz during maneuvers (TBC for details, reference).  This is interpolated to the times of data observation (ref to method), corrected for the wobble and other time-dependent offsets determined from the observed positions of a large number of sources around the sky, and finally converted to the LOS of each detector using the quaternions in the IMO (which are determined from observations of bright planets - see the Focal plane reconstruction pipeline).
 
 
''Details of delivery are TBD''
 
 
== FITS file structure ==
 
 
The FITS files will begin with a minimal primary header that will be followed by several BINTABLE extensions: the first one for the OBT and its (global) flag, the following ones for each detector signal data and its (local) flag. 
 
 
Filenames will be of the form ''{H|L}FI_HscN-DDDD-R-yyymmdd.fits'', where ''DDDD'' is the OD number, ''sc'' indicates science data, and N=1-5 for the 5 HFI  files, and ''R'' indicates it is reduced (i.e., cleaned and calibrated) data.
 
 
''NB. this is the current name used in DPC exchanges, perhaps it should be changed … eg. replace the date with the release number. Will also indicate that they are calibrated in astrophysical units and will have the dipoles removed, thus they are for delivery to the external community.''
 
 
=== Header keywords ===
 
 
An example is given below.
 
 
 
==== EXTENSION 0: ====
 
 
SIMPLE  =                    T / file does conform to FITS standard           
 
BITPIX  =                  32 / number of bits per data pixel                 
 
NAXIS  =                    0 / number of data axes                           
 
EXTEND  =                    T / FITS dataset may contain extensions           
 
COMMENT  FITS (Flexible Image Transport System) format is defined in 'Astronomy
 
COMMENT  and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
 
EFDD_VER= '99.9    '                                                           
 
ICD_VER = '99.9    '                                                           
 
IMO    = 'IMO_2_62'                                                           
 
DATE    = '2012-09-04T13:45:59' / file creation date (YYYY-MM-DDThh:mm:ss UT) 
 
END                                                                           
 
 
where EFDD_VER and ICD_VER are the versions of the respective documents in which the structure is defined (dummy values in the example).
 
 
 
==== EXTENSION 1: OBT  ====
 
 
 
XTENSION= 'BINTABLE'          / binary table extension                       
 
BITPIX  =                    8 / 8-bit bytes                                   
 
NAXIS  =                    2 / 2-dimensional binary table                   
 
NAXIS1  =                    9 / width of table in bytes                       
 
NAXIS2  =            15573106 / number of rows in table                       
 
PCOUNT  =                    0 / size of special data area                     
 
GCOUNT  =                    1 / one data group (required keyword)             
 
TFIELDS =                    2 / number of fields in each row                 
 
TTYPE1  = 'OBT    '          / label for field  1                           
 
TFORM1  = '1K      '          / data format of field: 8-byte INTEGER         
 
TUNIT1  = '2**(-16)sec'        / physical unit of field                       
 
TTYPE2  = 'Flag    '          / label for field  2                           
 
TFORM2  = '1B      '          / data format of field: BYTE                   
 
TUNIT2  = 'N/A    '          / physical unit of field                       
 
EXTNAME = 'OBT    '          / name of this binary table extension           
 
TIMEZERO= '1660237181'                                                         
 
END                                                                           
 
 
 
 
where TIMEZERO is the value of the first timesample  in the units of TUNIT1
 
 
 
==== EXTENSION 2: 14_545_1_LFER4_JC_v51 ====
 
 
This is the first of the extensions containing the detector data, and is followed by more like it for the other detectors.
 
 
XTENSION= 'BINTABLE'          / binary table extension                       
 
BITPIX  =                    8 / 8-bit bytes                                   
 
NAXIS  =                    2 / 2-dimensional binary table                   
 
NAXIS1  =                    5 / width of table in bytes                       
 
NAXIS2  =            15573106 / number of rows in table                       
 
PCOUNT  =                    0 / size of special data area                     
 
GCOUNT  =                    1 / one data group (required keyword)             
 
TFIELDS =                    2 / number of fields in each row                 
 
TTYPE1  = 'Signal  '          / label for field  1                           
 
TFORM1  = '1E      '          / data format of field: 4-byte REAL             
 
TUNIT1  = 'KCMB    '          / physical unit of field                       
 
TTYPE2  = 'Flag    '          / label for field  2                           
 
TFORM2  = '1B      '          / data format of field: BYTE                   
 
TUNIT2  = 'N/A    '          / physical unit of field                       
 
EXTNAME = '14_545_1_LFER4_JC_v51' / name of this binary table extension       
 
TIMEZERO= '1660237181'                                                         
 
CHANNEL = '545-1  '                                                           
 
END                                                                           
 
 
Note that NAXIS must be the same for all extensions.
 
 
''NB. may want to change EXTNAME to be just the detector name; the rest was for internal purposes only''
 
  
  
  
 
[[Category:Mission science products|001]]
 
[[Category:Mission science products|001]]

Revision as of 07:54, 15 March 2013

This section intentionally left empty