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

Table 

to give, e.g., filter transmission profiles or noise power spectra

Map 

namely 2-D "flat" maps, to give, e.g., the main beam shape

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

---

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.

The detector parameter data are given in the form of a table giving the parameter values for each detector. The table columns (whose names are in BOLD ITALICS) are:

Bolometer name - 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. These parameters are derived from observations of bright planets; see Detectors pointing & beam for details.

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). These values are determined from ground-based measurements.

Beam parameters - FWHM, ELLIPTICITY, POSANG 

These are the mean FWHM of the scanning beam (in arcmin, 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; details in Detectors pointing & beam.

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). These values are determined from the signal timelines as described in TOI processing chapter.

In the HFI RIMO, this table includes entries for the RTS bolometers (143-8 and 545-3), which are approximate or 0.00 when not evaluated.

The basic structure of the BINTABLE extension is as follows:

;-----------------------------------------------------------------------------
; Detector parameters
;-----------------------------------------------------------------------------
XTENSION= 'BINTABLE'           / binary table extension                         
BITPIX  =                    8 / array data type                                
NAXIS   =                    2 / number of array dimensions                     
NAXIS1  =                  120 / length of dimension 1                          
NAXIS2  =                   52 / length of dimension 2                          
PCOUNT  =                    0 / number of group parameters                     
GCOUNT  =                    1 / number of groups                               
TFIELDS =                   15 / number of table fields                         
EXTNAME = 'CHANNEL PARAMETERS' / extension name                                 
TTYPE1  = 'DETECTOR'                                                            
TFORM1  = '8A      '                                                            
TUNIT1  = 'n/a     '                                                            
TTYPE2  = 'PHI_UV  '                                                            
TFORM2  = 'D       '                                                            
TUNIT2  = 'deg     '                                                            
TTYPE3  = 'THETA_UV'                                                            
TFORM3  = 'D       '                                                            
TUNIT3  = 'deg     '                                                            
TTYPE4  = 'PSI_UV  '                                                            
TFORM4  = 'D       '                                                            
TUNIT4  = 'deg     '                                                            
TTYPE5  = 'PSI_POL '                                                            
TFORM5  = 'D       '                                                            
TUNIT5  = 'deg     '                                                            
TTYPE6  = 'EPSILON '                                                            
TFORM6  = 'D       '                                                            
TUNIT6  = 'n/a     '                                                            
TTYPE7  = 'FWHM    '                                                            
TFORM7  = 'D       '                                                            
TUNIT7  = 'arcmin  '                                                            
TTYPE8  = 'ELLIPTICITY'                                                         
TFORM8  = 'D       '                                                            
TUNIT8  = 'n/a     '                                                            
TTYPE9  = 'POSANG  '                                                            
TFORM9  = 'D       '                                                            
TUNIT9  = 'deg     '                                                            
TTYPE10 = 'NET     '                                                            
TFORM10 = 'D       '                                                            
TUNIT10 = 'K*s^1/2 '                                                            
TTYPE11 = 'F_KNEE  '                                                            
TFORM11 = 'D       '                                                            
TUNIT11 = 'Hz      '                                                            
TTYPE12 = 'ALPHA   '                                                            
TFORM12 = 'D       '                                                            
TUNIT12 = 'n/a     '                                                            
TTYPE13 = 'F_MIN   '                                                            
TFORM13 = 'D       '                                                            
TUNIT13 = 'Hz      '                                                            
TTYPE14 = 'F_MAX   '                                                            
TFORM14 = 'D       '                                                            
TUNIT14 = 'Hz      '                                                            
TTYPE15 = 'F_SAMP  '                                                            
TFORM15 = 'D       '                                                            
TUNIT15 = 'Hz      '

Map-level parameter data

The map-level data table contains the effective beam solid angle (total and out to different multiples of the beamFWHM) and noise information as follows:

FREQUENCY 

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

Omega_total

total beam solid angle in armin^2

Ometa_1fwhm 

beam solid angle out to 1FWHM in arcmin^2

Omega_2fwhm 

beam solid angle out to 2FWHM in arcmin^2

FWHM_eff 

FWHM of a Gaussian beam having the same (total) solid angle, in sr. This is the best value for source flux determination

FWHM_gauss 

FWHM derived from best Gaussian fit to beam maps, in sr. This is the best value for source identification

NOISE 

This is the typical noise/valid observation sample as derived from an appropriate combination of the NETs of the valid detectors used in the map.

For the Omega columns, the 'DISP' (for dispersion) column gives an estimate of the spatial variation as a function of position on the sky. This is the variation induced by combining the scanning beam determined from the planet observations with the scanning strategy, as described in Detectors pointing & beam.

The BINTABLE extension has the following structure

TABLE TO BE ADDED

Single detector and combined bandpasses

There are no detector-level products in the first release, so there will be no detector-level bandpasses in the accompanying RIMO, but only the combined bandpasses

Detector noise spectra

There are no detector-level products in the first release, so there will be no detector noise spectra in the accompanying RIMO.

Beam Window Functions

Beam window functions and associated error descriptions are given into a BINTABLE for each detection unit, where detection unit consists of an auto or a cross product of one or two frequency maps or detset maps used in the likelihood. Here they are:

• the 6 HFI frequency channels, producing 21 extensions
• 26 detsets, producing 351 extensions; the detsets used are, by frequency channel:
  • 100_ds1, 100_ds2,
  • 143_ds1, 143_ds2, 143_5, 143_6, 143_7,
  • 217_ds1, 217_ds2, 217_1, 217_2, 217_3, 217_4,
  • 353_ds1, 353_ds2, 353_1, 353_2, 353_7, 353_8,
  • 545_1, 545_2, 545_4,
  • 857_1, 857_2, 857_3, 857_4

Each extension contains:

• a NOMINAL column (mandatory) with the window function proper,
• a BIAS column (optional),
• a number of EIGEN_n vectors, (5 for Release 1) of error modes.
• a keyword NUMVECT (Integer) specified the number of eigenmode vectors, and
• keywords LMIN and LMAX which give the length of nominal vector
• keywords LMIN_EM and LMAX_EM that give the range of the valid samples of the eigenmode vectors. Here LMAX_EM is always less than or equal to LMAX, and the values between LMAX_EM+1 and LMAX is set to NaN

An example of the FITS header is (Preliminary - to be updated):

;-----------------------------------------------------------------------------
; EXTENSION 11: BEAM_143_DS1X143_5
;----------------------------------------------------------------------------- 
XTENSION= 'BINTABLE'           / binary table extension                           
BITPIX  =                    8 / array data type                                 
NAXIS   =                    2 / number of array dimensions                     
NAXIS1  =                   24 / length of dimension 1                          
NAXIS2  =                 4001 / length of dimension 2                          
PCOUNT  =                    0 / number of group parameters                     
GCOUNT  =                    1 / number of groups                               
TFIELDS =                    6 / number of table fields                         
TTYPE1  = 'NOMINAL '                                                            
TFORM1  = 'E       '                                                            
TTYPE2  = 'EIGEN_0 '                                                            
TFORM2  = 'E       '                                                            
TTYPE3  = 'EIGEN_1 '                                                            
TFORM3  = 'E       '                                                            
TTYPE4  = 'EIGEN_2 '                                                            
TFORM4  = 'E       '                                                            
TTYPE5  = 'EIGEN_3 '                                                            
TFORM5  = 'E       '                                                            
TTYPE6  = 'EIGEN_4 '                                                            
TFORM6  = 'E       '                                                            
EXTNAME = 'BEAM_143_DS1X143_5' / extension name                                 
NUMVECT =                    5 / Number of eigenvectors                         
END

Beam Correlation Matrix

Two of these matrices are given, one for the frequency channels (21x21) and one for the detsets (351x351). Each is a symmetric matrix with 1-valued diagonal, made of NBEAMS*NBEAMS blocks, each block being NMODES*NMODES in size. Each row- (and column-) block entry relates to the B(l) model whose name is indicated in ROW* keywords below, and the corresponding eigenmodes are stored in a HDU of the same name.

The header is of the form (Preliminary - to be updated)::

;-----------------------------------------------------------------------------
; EXTENSION 381: CORRBEAM_DET
;----------------------------------------------------------------------------- 
XTENSION= 'IMAGE   '           /                                                
EXTNAME = 'CORRBEAM_DET'       /                                                
BITPIX  =                  -32 / IEEE single precision floating point           
NAXIS   =                    2 /                                                
NAXIS1  =                 1755 /                                                
NAXIS2  =                 1755 /                                                
DATE    = '2012-11-23'         / Creation date (CCYY-MM-DD) of FITS header      
 …
NDETS   =                   26 / number of detector assemblies                  
NBEAMS  =                  351 / number of beams = NDETS*(NDETS+1)/2            
NMODES  =                    5 / number of eigen modes for each beam B(l)       
DATAMIN =            -0.979880 / minimum value (should be >=-1)                 
DATAMAX =              1.00000 / maximum value (should be 1)                    
ROW1    = 'BEAM_100-DS1x100-DS1' / block #1 on row (or column)                  
ROW2    = 'BEAM_100-DS1x100-DS2' / block #2 on row (or column)                  
ROW3    = 'BEAM_100-DS1x143-DS1' / block #3 on row (or column)                  
...
ROW350  = 'BEAM_857-3x857-4'   / block #350 on row (or column)                  
ROW351  = 'BEAM_857-4x857-4'   / block #351 on row (or column)                  
END