Difference between revisions of "Glossary"
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Revision as of 18:06, 3 July 2014
- 4K lines: EMI/EMC influence of the 4K cooler mechanical motion on the bolometer readout electronics.
- calibration [HFI meaning]: For a single detector, the absolute calibration is gain factor between the measured signal (watts absorbed by the detector) and the sky signal (in astrophysical units); can vary with time. For a set of detectors, the relative calibration is the difference in the calibration between detector pairs. The latter can be measured very accurately from the observations of the same source by different detectors, and is only slightly affected by the differences in the detector spectral responses, which are similar; the former requires observations of sources with well modeled spectral energy distributions or well known spectra, and requires that the detector's spectral bandpass also be well known.
- calibration: [LFI meaning]: absolute calibration refers to the 0th order calibration for each channel, 1 single number, while the relative calibration refers to the component of the calibration that varies pointing period by pointing period.
- detector set [HFI meaning]: a detector set (aka detset aka quad) is a combinaison of two pairs of Polarization Sensitive Bolometers pairs at the proper orientations. The lists of detsets is given in here.
- DMC : Data Management Component, the databases used at the HFI and LFI DPCs
- effective beam [HFI meaning]: 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.
- far sidelobe [HFI meaning]: the response to the sky of a detector more than 5 degrees from the beam centroid.
- half ring difference : difference between the map built using the first half of each pointing period (typically 20 minutes of contiguous data) and the one built with the second half. This difference effectively removes the sky signal and most of the correlated noise, leaving only the noise components that have time scales of < ~ 20 min.
- HEALPix: (Hierarchical Equal Area isoLatitude Pixelation of a sphere, #gorski2005) pixelation used to produce Planck sky maps (and HFI HPR).
- HPR [HFI meaning]: HEALPix Rings are introduced to avoid any additional binning of the data. We choose a sky pixelization as a basis for this ring making. HPR are therefore partial sky maps produced via a projection onto the sky of each single pointing period separately.
- IMO [HFI meaning]: the HFI Instrument MOdel 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.
- jump : sudden change of the baseline level inside a ring
- main beam [HFI meaning] Response to the sky within 23 arcminutes of the centroid of response.
- near sidelobe [HFI meaning] Response to the sky between 23 arcminutes and 5 degrees from the main beam centroid.
- OD : 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.
- optical beam [HFI meaning] The response to the sky due to optics alone.
- PBR [HFI meaning]: Phase Bin Rings provide a compressed and higher signal-to-noise ratio rendition of the original Time Order Data
- polarization leakage [HFI meaning]: 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.
- ring [HFI meaning]: 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.
- RIMO [HFI meaning]: 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.
- sample [HFI meaning]
- scanning beam [HFI meaning]: 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.
- scanning beam [LFI meaning]: the actual beam which couples the optics of the instrument with the scanning movement of the satellite (beam smearing). It can be measured from planet observations.
- SOVT : System Operation and Validation Test
- spectral response (or bandpass): steady state response of a detector system (i.e., detector and its electronics + horn + filter) as a function of frequency. It does not consider the temporal response and associated transfer function.
- survey [HFI meaning]: sky surveys (aka Scan #)are defined in terms of the direction of the satellite's spin axis. Survey periods are given here.
- TOD [HFI meaning]: Time-Ordered Data
- TOD [LFI meaning]: Time-Ordered Data, refers to calibrated data
- TOI [HFI meaning]: Time Ordered Information
- TOI [LFI meaning]: Time Ordered Information, refers to uncalibrated data
- warm units : JFET, Bellow, PAU et REU
EMI/EMC influence of the 4K cooler mechanical motion on the bolometer readout electronics.
[LFI meaning]: absolute calibration refers to the 0th order calibration for each channel, 1 single number, while the relative calibration refers to the component of the calibration that varies pointing period by pointing period.
(Planck) High Frequency Instrument
(Planck) Low Frequency Instrument
Data Management Component, the databases used at the HFI and LFI DPCs
difference between the map built using the first half of each pointing period (typically 20 minutes of contiguous data) and the one built with the second half. This difference effectively removes the sky signal and most of the correlated noise, leaving only the noise components that have time scales of < ~ 20 min.
(Hierarchical Equal Area isoLatitude Pixelation of a sphere, <ref name="Template:Gorski2005">HEALPix: A Framework for High-Resolution Discretization and Fast Analysis of Data Distributed on the Sphere, K. M. Górski, E. Hivon, A. J. Banday, B. D. Wandelt, F. K. Hansen, M. Reinecke, M. Bartelmann, ApJ, 622, 759-771, (2005).
Data Processing Center
sudden change of the baseline level inside a ring
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.
Daily Tele-Communication Period
Flexible Image Transfer Specification
System Operation and Validation Test
JFET, Bellow, PAU et REU
JFET, Bellow, PAU et REU
Junction Field Elect Transistor
Readout Electronic Unit