Planck-LFI: Design and Performance of the 4 Kelvin Reference Load Unit

Abstract

The LFI radiometers use a pseudo-correlation design where the signal from the sky is continuously compared with a stable reference signal, provided by a cryogenic reference load system. The reference unit is composed by small pyramidal horns, one for each radiometer, 22 in total, facing small absorbing targets, made of a commercial resin ECCOSORB CR (TM), cooled to approximately 4.5 K. Horns and targets are separated by a small gap to allow thermal decoupling. Target and horn design is optimized for each of the LFI bands, centered at 70, 44 and 30 GHz. Pyramidal horns are either machined inside the radiometer 20K module or connected via external electro-formed bended waveguides. The requirement of high stability of the reference signal imposed a careful design for the radiometric and thermal properties of the loads. Materials used for the manufacturing have been characterized for thermal, RF and mechanical properties. We describe in this paper the design and the performance of the reference system.

This is an author-created, un-copyedited version of an article accepted for publication in JINST. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at [10.1088/1748-0221/4/12/T12006]. 14 pages, 34 figures

References in corpus (11)

• The Cosmic Microwave Background Spectrum from the Full COBE/FIRAS Data Set
• Calibrator Design for the COBE Far Infrared Absolute Spectrophotometer (FIRAS)
• 1/f noise and other systematic effects in the Planck-LFI radiometers
• Removing 1/f noise stripes in cosmic microwave background anisotropy observations
• Cryogenic characterization of the Planck sorption cooler system flight model
• Offset balancing in pseudo-correlation radiometers for CMB measurements
• Design, development, and verification of the Planck Low Frequency Instrument 70 GHz Front-End and Back-End Modules
• The linearity response of the Planck-LFI flight model receivers
• The Planck Low Frequency Instrument
• The Low Frequency Instrument in the ESA Planck mission
• Analysis of thermally-induced effects in Planck Low Frequency Instrument

Cited by in corpus (25)

• Planck pre-launch status: Design and description of the Low Frequency Instrument
• Planck Early Results. II. The thermal performance of Planck
• Planck early results. III. First assessment of the Low Frequency Instrument in-flight performance
• Planck pre-launch status: the Planck-LFI programme
• Planck 2013 results. V. LFI calibration
• Planck 2013 results. III. LFI systematic uncertainties
• Planck pre-launch status: Low Frequency Instrument calibration and expected scientific performance
• Planck-LFI radiometers' spectral response
• Exploring cosmic origins with CORE: effects of observer peculiar motion
• Noise Properties of the Planck-LFI Receivers
• Design, development, and verification of the Planck Low Frequency Instrument 70 GHz Front-End and Back-End Modules
• The linearity response of the Planck-LFI flight model receivers
• Direct comparison of sterile neutrino constraints from cosmological data, ${\nu }_e$ disappearance data and ${\nu }_{\mu }\to {\nu }_e$ appearance data in a $3+1$ model
• Planck pre-launch status: calibration of the Low Frequency Instrument flight model radiometers
• Optimization of Planck/LFI on--board data handling
• Planck-LFI radiometers tuning
• The Planck-LFI flight model composite waveguides
• Thermal susceptibility of the Planck-LFI receivers
• Permittivity and permeability of epoxy-magnetite powder composites at microwave frequencies
• In-flight calibration and verification of the Planck-LFI instrument
• Dynamic validation of the Planck/LFI thermal model
• Cryogenic environment and performance for testing the Planck radiometers
• Advanced modelling of the Planck-LFI radiometers
• Readout system with on-board demodulation for CMB polarization experiments using coherent polarimeter arrays
• In-flight measurement of Planck telescope emissivity