The JPL and DSN convention for Doppler frequency shift is (Δ ν)DSN = ν0 − ν, where ν is the measured frequency and ν0 is the reference frequency. It is positive for a spacecraft receding from the tracking station (red shift), and negative for a spacecraft approaching the station (blue shift), just the opposite of the usual convention, (Δ ν)usual = ν − ν0. In consequence, the velocity shift, Δv = v − v0, has the same sign as (Δ ν)DSN but the opposite sign to (Δ ν)usual. Unless otherwise stated, we use the DSN frequency shift convention in this document.