Radial velocity maps for a single snapshot of a subhalo during its infall into the host halo for one of the codes. The white solid circle represents ${\mathrm{R}}_{\mathrm{vir}}^{\mathrm{sub}}$, while the dashed green circles indicate $0.2{\mathrm{R}}_{\mathrm{vir}}^{\mathrm{sub}}$ and $0.3{\mathrm{R}}_{\mathrm{vir}}^{\mathrm{sub}}$. We calculate the rate of inflowing gas in the $0.1{\mathrm{R}}_{\mathrm{vir}}^{\mathrm{sub}}$ sized shell at $0.2{\mathrm{R}}_{\mathrm{vir}}^{\mathrm{sub}}$ radii from the center of the subhalo. Left: Original radial velocity map before corrections. As our subhalo moves through the host CGM, CGM gas in the direction of motion will be observed as infalling gas with a negative radial velocity, while the gas it leaves behind will be seen as an outflow with a positive radial velocity. Center: Mock map showing how the radial velocity map would appear exclusively due to the effect of the subhalo's motion relative to the host CGM. Right: Radial velocity map after subtracting the radial velocity values from the mock map for all gas cells except those associated with the subhalo (i.e., cells with velocities relative to the subhalo <2σ_sub and within ${\mathrm{R}}_{\mathrm{vir}}^{\mathrm{sub}}$). After this correction, we can accurately identify the radial velocity of the gas relative to the satellite without introducing the effects of the CGM gas motion during its infall, allowing us to determine the subhalo's inflow mass rate during infall.