Space-borne interferometric gravitational wave detectors, sensitive in the low-frequency (millihertz) band, will fly in the next decade. In these detectors the spacecraft-to-spacecraft light-travel-times will necessarily be unequal, time-varying, and (due to aberration) have different time delays on up- and down-links. Reduction of data from moving interferometric laser arrays in solar orbit will in fact encounter non-symmetric up- and downlink light time differences that are about 100 times larger than has previously been recognized. In order to account for these effects, and effectively remove the laser frequency fluctuations from the Doppler data LISA will measure, a new set of time-delay interferometric combinations is needed. A general procedure for their derivation, based on non-commuting time-delay operators, will be presented.