The RIMO

Overview

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. It is described in detail in The HFI and LFI RIMO ICD (ref). There will be two RIMOs, one for each instrument, which will follow the same overall structure, but will differ in the details. The type of data in the RIMO can be:

Parameter 

namely scalers to give properties such as a noise level or a representative beam FWHM

Table 

to give filter transmission profiles or noise power spectra

Map 

to give beam shape

The different types of data are written into different BINTABLE extensions of the FITS file, and these are described below.

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Outstanding business:

• common or mixed items, like, eventually cross beam window functions between an HFI and an LFI beam

Detector-level parameter data

There are no detector-level products in the first release, so there will be no detector-level parameters in the accompanying RIMO. This section will serve for later releases.

The detector parameter data are given in the form of a table giving the parameter values for each detector. The table columns are (with the column names in parentheses):

DETECTOR

These are the detector names. For HFI these will be of the form 217-3 for SWBs or 100-3b for PSBs, and for LFI they will have the form 27M or 18S. There are 52 HFI detectors and 22 LFI detectors.

Focal plane geometry parameters - PHI_UV, THETA_UV, and PSI_UV 

These parameters give the geometry of the focal plane, or the positions of the detectors in the focal plane. The angles that give the rotation of the beam pattern from a fiducial orientation (forward beam direction (z-axis) pointing along the telescope line of sight, with y-axis aligned with the nominal scan direction) to their positions in the focal plane. The fiducial position is that given by the Star Tracker. All angles are in radians.

Polarization parameters - PSI_POL, EPSILON 

These are the direction of maximum polarization, defined with the beam in the fiducial orientation described above, that is, before rotation onto the detector position, and the cross-polarization contamination (or leakage).

Beam parameters - FWHM, ELLIPTICITY, POSANG 

These are the mean FWHM of the scanning beam (arcmin TBC), the beam ellipticity (no units), and the position angle of the beam major axis. The scanning beam is that recovered from the observation of bright planets.

Noise parameters

NET_TOT, NET_WHT, F_KNEE, ALPHA :

Two NETs are given: one determined from the total noise (rms of the noise timeline) and one determined from the white noise level of the noise spectrum. The F_KNEE and ALPHA parameters are the frequency where the 1/f noise component meets the white noise level, and the slope of the former. The NETs are in units of Kcmb or MJy/sr * sqrt(s).

Map-level parameter data

FREQUENCY 

a 3-digit string giving the reference frequency in GHz, i.e., of the form 044 or 217

Beam parameters - FWHM ;

These are the FWHM (in rad) of the effective beam and its solid angle (in sr)

Noise parameter - NOISE ;

This is TBD: noise/observation sample or ...

Single detector and combined bandpasses

The effective filter bandpasses are given in different BINTABLE extensions. The extension is named BANDPASS_{name}, where name specified the detector or the map. In the case of the maps, the bandpasses are a weighted average of the bandpasses of the detectors that are used to built the map. For details see ref to 03d HFI_Spectral Band. The bandpasses are given as 4-column tables containing

• the wavenumber (cm-1)
• the transmission (normalized to 1 at the max for HFI and to have an integral of 1 for LFI)
• the uncertainty
• a flag

Detector noise spectra

The noise power spectra are the result of the detnoise pipeline.

HFI

these are the ring noise spectra averaged for rings NN to MM in order to give a representative spectrum. The spectra of all 50 valid bolometers are given in a single table.

LFI 

TBW

The keyword F_NYQ gives the Nyquist frequency, and can be used together with the number of points in the spectrum to reconstruct the frequency scale.

Beam Window Functions

Beam window functions and associated error descriptions are given into a BINTABLE for each detection unit. The NOMINAL column is mandatory, the BIAS column is optional, and the number of EVECT is variable. The keyword NEVEC indicates how many there are in order to ease the automatic reading