Optical beam models

Introduction

Models of the optical performance of Planck were developed using the GRASP package developed by TICRA. We provide here the models and the modelled performance for the three most-used instances:

• the Radio-Frequency Qualification Model (RFQM) was a full-size duplicate of the optical system of Planck (telescope with all ancillary structure and baffling) with a representative focal plane containing a few detectors only over the range 30 to 320 GHz. The beam patterns of this system were extensively measured at room temperature in a Compact Array Test Chamber, and compared to a GRASP model. The GRASP geometrical and computational model was refined to match the measured performance. The final GRASP model is referred to as the RFQM model.
• The Radio-Frequency Flight Model (RFFM) used the computational model derived on the RFQM and implemented the predicted in-flight (cryogenic temperature) geometry of Planck. The GRASP RFFM model was used to predict the beam patterns of all Planck detectors in flight, which were in turn used during the analysis of Planck data.
• the RFFM2 GRASP model is a modified version of RFFM which was derived by fitting in-flight measurements of the Planck beam patterns obtained from observations of planets. This model has not been used in the scientific analysis of Planck data.

More information on the RFQM and RFFM can be found in "Planck pre-launch status: The optical system": Planck-PreLaunch-II. More information on the comparison of RFFM predictions to in-flight measurements, and on the derivation of the RFFM2 model, can be found in "Characterization of the in-flight properties of the Planck telescope": Tauber et al. 2019.

RFQM

All files related to the RFQM GRASP model are contained in the file RFQM.zip .

The zip file contains the following elements:

• Folder 2008_TICRA_RFQM_model contains the GRASP configuration files
• Folder RFQM_4pi_patterns contains the calculated 4Pi patterns
• Docs:
  • Inputs for the RFQM prediction numerical model
  • RFQM main lobe CATR numerical model
  • Planck RFQM Evaluation Report
  • S1287-01: RF analysis of far-out side lobes from RFQM
  • S-1287-07: RF performance from measured mirrors

RFFM

All files related to the RFFM GRASP model are contained in the file RFFM.zip.

The zip file contains the following elements:

• Folder synthesis_TICRA_model&data_2009: contains the numerical model used to compute RFFM and explicatory notes, and a selection of computed patterns
• Folder RFFM_main_beam_nominal: contains computed main beams, nominal config, all detectors, 5 freqs, 2 pols
• Folder RFFM_main_beam_nominal_BW_AV: contains computed main beams, nominal config, all detectors, averaged over 5 freqs, 2 pols
• Folder RFFM_4pi_nominal_Pxx_SC: contains computed 4Pi beams, nominal config, 30-27/70-23/100-1/353-1 dets, center freq, 1 pol, P_xx and SC coordinates
• Folder RFFM_4pi_multifrequency_nominal: contains computed 4Pi beams, nominal config, 30-27/70-23/100-1/353-1 dets, 5 freqs, 2 pols, P_xx and SC coordinates
• Folder RFFM_Quilting_juin_2009: contains model and computed patterns for three cases of reflector quilting
• General Docs:
  • Inputs for the RFFM Flight Prediction numerical model
  • Planck Flight performances analysis report
  • Planck PLM RF performance analysis
  • Planck Payload optical performance analysis
  • Planck Flight performances analysis report
  • RFFM test evaluation report of reference test horn radiation pattern measurements

RFFM2

All files related to the RFFM2 GRASP model are contained in the file RFFM2.

The zip file contains the following elements:

• RFM2-GRASP9 contains the files for the retrieval of RFM2 and the total telescope geometry of RFM2. In order to use these files some named paths depending on the computer must be changed.
  • Folders Detectors and Geometry contain the configuration inputs to GRASP
• Folder POS contains the analysis calls to POS and GRASP (directory and file names need to be renamed to local values)
  • Folder Final-33-RFM2/final_result contains the computed pattern for each detector (field.grd and power.grd)

• RFM2-GRASP9: a GRASP10 project with the RFM2 geometry, which can be used directly without changing file names. It only contains one computed pattern at 30 GHz.

• Docs:
  • S-1563-12: In-flight Retrieval of Geometrical information on the Planck Telescope: Alternative Geometry retrieval using LFI beam data from all Jupiter scans
  • S1563-13: In-flight Retrieval of Geometrical information on the Planck Telescope RFM2: Geometry retrieval using combined HFI data and LFI beam data
  • S1563-14: In-flight Retrieval of Geometrical information on the Planck Telescope RFM2: RF performance of LFI beams
  • S1563-15: In-flight Retrieval of Geometrical information on the Planck Telescope RFM2: RF performance of HFI beams
  • S1599-WP4: In-flight Retrieval of Geometrical information on the Planck Telescope: RF performance of detectors extended with wide-band nature for RFM2
  • A&A Dec 2018: Characterization of the in-flight properties of the Planck telescope