Planck pre-launch status: Calibration of the Low Frequency Instrument flight model radiometers

¹ INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, via P. Gobetti, 101, 40129 Bologna, Italy e-mail: villa@iasfbo.inaf.it
² Department of Physics, University of California, Santa Barbara, 93106-9530, USA

³ University of Helsinki, Department of Physics, PO Box 64, 00014 Helsinki, Finland
⁴ Helsinki Institute of Physics, PO Box 64, 00014 Helsinki, Finland
⁵ Metsähovi Radio Observatory, Helsinki University of Technology, Metsähovintie 114, 02540 Kylmälä, Finland
⁶ Thales Alenia Space Italia S.p.A., S.S. Padana Superiore 290, 20090 Vimodrone (MI), Milano, Italy
⁷ Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy
⁸ DA-Design Oy. (aka Ylinen Electronics), Keskuskatu 29, 31600 Jokioinen, Finland
⁹ IFP-CNR, via Cozzi 53, 20125 Milano, Italy
¹⁰ INAF - Osservatorio Astronomico di Trieste, 11 via Tiepolo, 34143 Trieste, Italy
¹¹ University of Trieste, Department of Physics, 2 via Valerio, 34127 Trieste, Italy
¹² Jodrell Bank Centre for Astrophysics, Alan Turing Building, The University of Manchester, Manchester, M13 9PL, UK
¹³ Planck Science Office, European Space Agency, ESAC, PO box 78, 28691 Villanueva de la Cañada, Madrid, Spain
¹⁴ INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, via E. Bassini 15, 20133 Milano, Italy
¹⁵ Universidad de Cantabria, Dep. De Ingenieria de Comunicaciones. Av. Los Castros s/n, 39005, Santander-Spain
¹⁶ Instituto de Fisica de Cantabria (CSIC-UC), Av. Los Castros s/n, 39005 Santander, Spain
¹⁷ Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, USA

¹⁸ Instituto de Astrofísica de Canarias C/, Via Lactea s/n, 38205 La Laguna (Tenerife), Spain
¹⁹ National Radio Astronomy Observatory, Stone hall, University of Virginia, 520 Edgemont road, Charlottesville, USA
²⁰ MilliLab, VTT Technical Research Centre of Finland, Tietotie 3, Otaniemi, Espoo, Finland

Received: 9 July 2009
Accepted: 3 May 2010

Abstract

The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries eleven radiometer subsystems, called radiometer chain assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20 K and the back-end at 300 K, and with an external input load cooled to 4 K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e.g. 1/f noise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential inputs to the Planck-LFI data analysis.