TOI processing
This Section is kept short as this Planck release does not contain TOIs. The main information in the HFI processing paper is not duplicated here.
Contents
Overview[edit]
We describe here the how the TOIs are processed in order to be used for map production. We do not repeat the general features of the pipeline which are given in the HFI Data Processing article (REF). Here we give complementary explanations on some details. The TOI of each bolometer is processed independently of the other bolometers, so as to keep the noise properties as uncorrelated as possible. The processing involves modifying the TOI itself for what concerns the conversion to absorbed power and the correction of glitch tails. It also adds a flag TOI that masks the TOI samples that are not to be projected on maps for various reasons.
Input TOI[edit]
The input TOI consists in the AC modulated voltage output of the readout of each bolometer. The input has previously been decompressed, and converted from internal digital units to voltage via a constant factor. The TOI has a regular sampling at the acquisition frequency of facq=180.373700+-0.000050 Hz. There are almost no missing data in the TOIs, except for few hundred samples of 545 and 857GHz TOIs which are lost in the on-board compression due to saturation on the Galactic Center crossings.
General Pipeline Structure[edit]
The figure on the right shows how the initial ccTOI is transformed and how flags are produced:
Output TOIs and products[edit]
A TOI of clean calibrated samples (ccTOI) and a combined flag TOI (fTOI) are the outputs of the processing. The ccTOI is calibrated so as to represent the instantaneous power absorbed by the detector up to a constant (which will be determined by the map-making destriper). It is worth mentioning how the ccTOI is changed with respect to the input TOI, beyond the harmless constant conversion factor from voltage to absorbed power. The demodulation stage allows to get the demodulated bolometer voltage. The non-linearity correction is a second-order polynomial correction based on the physical but static bolometer model. In order to avoid too much masking after glitches, a glitch tail is subtracted after an occurrence of a glitch in the TOI. The 4K cooler lines noise is substituted at a series of 9 single temporal frequencies. Finally, the temporal response of the bolometer is deconvolved. This affects mostly the high-temporal frequency part of the TOI, although a small but significant low frequency (the long time response) tail is corrected too. Although flagged samples are not projected, their value influences the valid samples somehow. Hence interpolation procedures introduce some indirect modifications of the TOI. The flag TOI is a combination a dozen flags with an OR logic. Only unflagged data are projected. The exhaustive list of flags is given here: CompressionError, NoData, SSO, UnstablePointing, Glitch, BoloPlateFluctuation, RTS, Jump, PSBab. A complete qualification of the data is obtained at the ring level. If the TOI shows an anomalous behaviour on a given ring, this ring is discarded from projection. A special production of TOIs is also made as an input to the beam analysis with Mars, Jupiter and Saturn.
Examples of clean TOIs[edit]
Samples of PBR, TOIs, and PSDs of all detectors are shown in this file
Trends in the output processing variables[edit]
Here we intend to show the trend of the systematic effects that are dealt with in the TOI processing. The full impact of each of them is analyzed in HFI-Validation.
ADC baseline[edit]
The following figure shows the ADC baseline which is used prior to demodulation (a constant offset is removed for clarity). This baseline is obtained by smoothing on an hour block average the undemodulated TOI on unflagged samples.
Glitch statistics[edit]
The glitch rate per channel is shown in this figure. For details, see copap.
The percentage of flagged data (mostly due to Cosmic Rays) at the ring level is shown in these examples. No smoothing was applied. Only valid rings are shown.
The complete set of plots is here
Thermal template for decorrelation[edit]
A simple linear decorrelation is performed using the 2 dark bolometers as a proxy of the bolometer plate temperature. Coupling coefficients were measured during the CPV phase.
4K cooler lines variability[edit]
The amplitude of the nine 4K cooler lines in aW at 10, 20, 30, 40, 50, 60, 70, 80 and 17 Hz is shown for 2 bolometers in the following figures. The trend is smoothed over 31 ring values after having discarded measurements done at a ring which is discarded for all bolometers.
The 4K cooler line coefficients of all bolometers are shown in this file
jump correction[edit]
A piecewise constant value is removed to the TOI if a jump is detected. See a jump example in this figure:
The number of jumps per day (all bolometers included) is shown in this figure:
The jumps are uncorrelated from bolometer to bolometer. The total number of jumps detected in the nominal and full mission is shown here:
Trends in noise and signal[edit]
The smooth TOIs of all detectors are shown in this file
Noise stationarity[edit]
This is not the final version but gives a good idea of power spectra at the detector level of rmsigTOIs. All PSDs can be seen in this file
The standard deviation per ring corrected by ring duration bias is given here, one per bolometer using only valid rings. No smoothing is applied (except a 31-point smoothing for the 545 and 857 GHz channels) but values for rings discarded for all bolometers are not used. The standard deviation is computed on samples valid for map-making which are also not affected by the Galaxy or the point-sources using the usual flags. Two examples are given here.
The full series of plots is here:
Standard deviation of rmsig TOIs at the ring level
Note the presence for 3 bolometers of a two-level noise system. No correction can be done for that effect. See one example here:
An example of the higher order statistics which are used to unveil rings affected by RTS problems.
Flag description[edit]
Input flags[edit]
These flags are used as inputs to the TOI processing
- The point-source flag (PSflag):
An earlier version of HFI point-source catalog is read back into a flag TOIs, at a given frequency. In practice, 5 sigma sources are masked within a radius of 1.3 FWHM (9, 7, 5, 5, 5, 5 arcmin at 100,143,217,353,545,857 GHz)
- the galactic flag (Galflag):
An earlier version of HFI maps is thresholded and apodized. The produced masks are read into flag TOIs. The retained threshold corresponds to a sky coverage of respectively 70, 70, 80, 90, 90, 90% at 100,143,217,353,545,857 GHz.
- Solar System Object flag
For the TOI flag, Mars, Jupiter, Saturn are flagged up to a radius of NbBeam= 2,3,3,4,4,4 times the fiducial FWHM (FWHM= 9, 7, 5, 5, 5, 5 arcmin at 100,143,217,353,545,857 GHz)
As an input to planet mask for maps, Mars, Jupiter, Saturn are flagged using a Coefficient depending on the planet (Factor_per_source) times NbBeam2 times FWHM, with
- Factor_per_Source1 = 1.1 (Mars)
- Factor_per_Source2 = 2.25 (Jupiter)
- Factor_per_Source3 = 1.25 (Saturn)
and
- NbBeam2 = 2.25 at 100 GHz
- NbBeam2 = 4.25 at 143 GHz
- NbBeam2 = 4.0 at 217 GHz
- NbBeam2 = 5.0 at 353 GHz
- NbBeam2 = 6.0 at 545 GHz
- NbBeam2 = 8.0 at 857 GHz
A small trailing tail is added to the mask to take into account the non-deconvolution of the planet signal which has been replaced by background values. The width of that tail is 10 % of the main flag diameter. The number of samples which are flagged are Factor_per_Source2 * AddSNafter with:
- AddSNafter1 = 10 at 100 GHz
- AddSNafter2 = 30 at 143 GHz
- AddSNafter3 = 20 at 217 GHz
- AddSNafter4 = 20 at 353 GHz
- AddSNafter5 = 30 at 545 GHz
- AddSNafter6 = 40 at 857 GHz
Uranus and Neptune are detected and masked by HFI.
24 asteroids have been detected with HFI at 857 GHz. They are masked at the TOI level using an exclusion radius of 1.5 FWHM (9, 7, 5, 5, 5, 5 arcmin at 100,143,217,353,545,857 GHz).
Those asteroids are:
- SSO_1Ceres
- SSO_2Pallas
- SSO_3Juno
- SSO_4Vesta
- SSO_7Iris
- SSO_8Flora
- SSO_9Metis
- SSO_10Hygiea
- SSO_11Parthenope
- SSO_12Victoria
- SSO_13Egeria
- SSO_14Irene
- SSO_15Eunomia
- SSO_16Psyche
- SSO_18Melpomene
- SSO_19Fortuna
- SSO_20Massalia
- SSO_29Amphitrite
- SSO_41Daphne
- SSO_45Eugenia
- SSO_52Europa
- SSO_88Thisbe
- SSO_704Interamnia
- SSO_324Bamberga
Output flags[edit]
With and without point-sources, identical to a and b PSBs.
Flags produced for the map making :
- UnstablePointing Flag OR FlagTOIproc OR SSOflag 4 map OR SSOflag seen
- FlagTOIproc = glitch OR jump OR flag thermal template
- PSB flag glitch = flag glitch A OR flag glitch B
Flag used in the destriping: same + point-source flag
(Planck) High Frequency Instrument
Solar System Object
random telegraphic signal
analog to digital converter
Calibration and Performance Verification
sudden change of the baseline level inside a ring
Full-Width-at-Half-Maximum