  An important goal of the Laser Interferometer Space Antenna (LISA) is to
observe a stochastic gravitational-wave background (SGWB). A study of possible
correlated noise in LISA is relevant to establish limits for this future
measurement. To test noise investigation methods under somewhat realistic
conditions, we use the data of LISA Pathfinder (LPF). We calculate the
coherence between the LPF differential acceleration of the two test-masses with
magnetic fields, temperature, and micronewton cold gas thruster activity in the
spacecraft. We apply our observed correlations to LISA, and estimate how the
presence of such correlated noise would affect its search for a SGWB. In the
context of a figure of merit, we estimate the effect of noise on the LISA SGWB
search.
