Glossary

This page gives definition of some words commonly used in this Explanatory Supplement.

• HFI detector set (aka detset aka quad) : a detector set is a combinaison of two pairs of Polarization Sensitive Bolometers pairs at the proper orientations. The lists of detsets is given in here.
• HFI effective beam : the effective beam at the map level is the overall angular response to the sky in a map pixel, which results from the combined effect of the instrumental response, the scanning strategy and the data processing.
• HFI focal plane geometry
• HFI HPR : HEALPix Rings are introduced to avoid any additional binning of the data. We choose a sky pixelization as a basis for this ring making (HEALPix, Górski et al. 2005). HPR are therefore partial sky maps produced via a projection onto the sky of each single pointing period separately.
• HFI IMO : the HFI IMO is a central repository containing the models (or a link to them) and sets of fixed parameters used in these models describing for example how photons are gathered and transformed into data. IMO is oriented toward the data reduction and data processing. IMO is also used to monitor the instrument health. IMO represents at any time the official knowledge of the instrument response. It is intended to represent its best current knowledge agreed on by the project and applicable to the data processing. IMO does not represent the knowledge of the instrument. It is a knowledge of its response, (e.g. how photons are gathered and transformed into data). It is a simplified fraction of this knowledge directly useful to reduce the data. The IMO is restricted to the sole parameters used in the DPC. IMO does not contain timelines, nor maps, although it can provide links to calibration timelines (e.g. gain evolution) and calibration maps (e.g. beam maps). Models do not need to be unique (not a single model for a single process). Depending on the purpose for which they are used, they can be more or less sophisticated. (e.g. bolometer models, beam representations, very simplified for first assessment of pointing parameters, ...). IMO does not choose between them : it contains the parameters for each of them at the same time. See HFI RIMO.
• HFI mission
• HFI optical beam
• HFI PBR : Phase Bin Rings provide a compressed and higher signal-to-noise ratio rendition of the original Time Order Data
• HFI polarization leakage : in general, systematic effects mix the I,Q,U signals. Given the amplitudes of the sky signals, leakage from temperature to polarisation can be dramatic for polarisation analysis.
• HFI ring : at the HFI DPC level the ring is the time intervalle between two First Thurster Firings as defined in AHF description document. It thus starts with a satellite slew and thus an unstable pointing period and continue with a satellite dwell and thus stable pointing period.
• HFI RIMO : The RIMO, or Reduced Instrument Model is a FITS file containing selected instrument characteristics that are needed by users who work with the released data products.
• HFI sample
• HFI scanning beam : the scanning is defined as the beam measured from the response to a point source of the full optical and electronic system, after the filtering.
• HFI survey (aka Scan #) : sky surveys are defined in terms of the direction of the satellite's spin axis. Survey periods are given here.