Difference between revisions of "Timelines"
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An example is given below. | An example is given below. | ||
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SIMPLE = T / file does conform to FITS standard | SIMPLE = T / file does conform to FITS standard | ||
Revision as of 16:36, 4 September 2012
There will be no timelines in the 1st data release …
Contents
Semi-raw signal timelines[edit]
HFI timelines[edit]
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[edit]
TBW
Cleaned and calibrated signal timelines[edit]
HFI processing[edit]
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[edit]
TBW
Pointing timelines[edit]
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[edit]
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[edit]
An example is given below.
EXTENSION 0:[edit]
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[edit]
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[edit]
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
(Planck) High Frequency Instrument
analog to digital converter
(Planck) Low Frequency Instrument
To be confirmed
sudden change of the baseline level inside a ring
Attitude History File
[ESA's] Mission Operation Center [Darmstadt, Germany]
Line Of Sight
To be defined / determined
Flexible Image Transfer Specification
On-Board Time
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.
Data Processing Center
Interface Control Document
