The phrase "orbital cycles" refers to the repetitive patterns or movements of an object in space, specifically in its orbit around another object. Full definition
But then the observed data are not perfect by any means and span a long time period (multiple orbital cycles) and so there may be some apples / oranges comparisons going on. (realclimate.org)
Kukla showed how past changes in orbital cycles very slightly altered the amount of solar energy hitting the Earth, leading to past glacial and interglacial periods. (skepticalscience.com)