Planck pre-launch status: Low Frequency Instrument optics M. Sandri, F. Villa, M. Bersanelli, C. Burigana, R. C. Butler, O. D'Arcangelo, L. Figini, A. Gregorio, C. R. Lawrence, D. Maino et al. (9 more) A&A, 520 (2010) A7 Published online: 15 September 2010 DOI: 10.1051/0004-6361/200912891