Characterization of Time Delay Interferometry combinations for the LISA instrument noise

Understand

Time delay interferometry (TDI) is a post-processing technique used in the Laser Interferometer Space Antenna (LISA) to reduce laser frequency noise by building an equal-arm interferometer via combining time-shifted raw phase measurements.

• The set of so-called 2nd generation TDI variables which sufficiently suppress laser frequency noise considering realistic LISA orbital dynamics has recently been expanded by a large number of additional solutions.
• In this paper, we characterize these new TDI channels by relating them to the well-known 1st generation variables $\alpha$, $\beta$, $\gamma$, and $\zeta$.
• We compute explicitly how each 2nd generation variable can be approximated as a linear combination of these four 1st generation variables, and show numerically that these approximations are accurate enough to model the noises not suppressed by TDI.