Wavelength dependence of the signal in the HARPS radial velocities. Parameter estimates for the velocities are calculated for six sets of 12 HARPS orders: radial velocity amplitude (top panel), signal period (middle panel), and signal phase when assuming a circular solution (bottom panel). The solid (dotted) red horizontal line denotes the estimate (99% credibility interval) obtained for the HARPS-TERRA velocities based on the reddest 50 orders (see Anglada-Escudé & Butler 2012). In the top panel, the squares and black lines denote the data rms for comparison. The horizontal error bars denote the wavelength range of the 12 HARPS orders used to obtain the radial velocities.