Optimization of Planck/LFI on--board data handling

• Published in: arXiv.org 2010-01
• Main Authors: Maris, M, Tomasi, M, Galeotta, S, Miccolis, M, Hildebrandt, S, Frailis, M, Rohlfs, R, Morisset, N, Zacchei, A, Bersanelli, M, Binko, P, Burigana, C, Butler, R C, Cuttaia, F, Chulani, H, D'Arcangelo, O, Fogliani, S, Franceschi, E, Gasparo, F, Gomez, F, Gregorio, A, Herreros, J M, Leonardi, R, Leutenegger, P, Maggio, G, Maino, D, Malaspina, M, Mandolesi, N, Manzato, P, Meharga, M, Meinhold, P, Mennella, A, Pasian, F, Perrotta, F, Rebolo, R, Turler, M, Zonca, A
• Format: Article
• Language: English
• Subjects: Algorithms; Computer simulation; Data analysis; Diagnostic systems; Ground tests; Noise; Onboard; Optimization; Prelaunch tests; Process parameters; Signal processing; Telemetry; White noise
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1001.4737

To asses stability against 1/f noise, the Low Frequency Instrument (LFI) onboard the Planck mission will acquire data at a rate much higher than the data rate allowed by its telemetry bandwith of 35.5 kbps. The data are processed by an onboard pipeline, followed onground by a reversing step. This paper illustrates the LFI scientific onboard processing to fit the allowed datarate. This is a lossy process tuned by using a set of 5 parameters Naver, r1, r2, q, O for each of the 44 LFI detectors. The paper quantifies the level of distortion introduced by the onboard processing, EpsilonQ, as a function of these parameters. It describes the method of optimizing the onboard processing chain. The tuning procedure is based on a optimization algorithm applied to unprocessed and uncompressed raw data provided either by simulations, prelaunch tests or data taken from LFI operating in diagnostic mode. All the needed optimization steps are performed by an automated tool, OCA2, which ends with optimized parameters and produces a set of statistical indicators, among them the compression rate Cr and EpsilonQ. For Planck/LFI the requirements are Cr = 2.4 and EpsilonQ