An "orbiter" is something that travels around or revolves around another object, like a satellite orbiting the Earth or a planet orbiting the sun. Full definition
Mars Reconnaissance Orbiter Mars Color Imager (MARCI): Instrument description, calibration, and performance J. F. Bell III, M. J. Wolff, M. C. Malin, W. M. Calvin, B. A. Cantor, M. A. Caplinger, R. T. Clancy, K. S. Edgett, L. J. Edwards, J. Fahle, F. Ghaemi, R. M. Haberle, A. Hale, P. B. James, S. W. Lee, T. McConnochie, E. Noe Dobrea, M. A. Ravine, D. Schaeffer, K. D. Supulver, and P. C. Thomas Journal of Geophysical Research 114, E08S92, doi: 10.1029 / 2008JE003315, 28 August 2009. (msss.com)
MSSS is also currently operating two cameras onboard NASA's 2005 Mars Reconnaissance Orbiter Mission (MRO), the Mars Color Imager (MARCI) and the Context Camera (CTX). (msss.com)
Panoramic lunar view taken by the Lunar Reconnaissance Orbiter Camera of the north rim of Cabeus crater. (sciencedaily.com)