A mid-term astrometric and photometric study of trans-Neptunian object (90482) Orcus J. L. Ortiz, A. Cikota, S. Cikota, D. Hestroffer, A. Thirouin, N. Morales, R. Duffard, R. Gil-Hutton, P. Santos-Sanz and I. de la Cueva A&A, 525 (2011) A31 Published online: 29 November 2010 DOI: 10.1051/0004-6361/201015309