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The SDSS-IV Mapping Nearby Galaxies at APO (MaNGA) program has been operatingfrom 2014-2020, and has now observed a sample of 9,269 galaxies in the lowredshift universe (z ~ 0.05) with integral-field spectroscopy. Withrest-optical (\lambda\lambda 0.36 - 1.0 um) spectral resolution R ~ 2000 theinstrumental spectral line-spread function (LSF) typically has 1sigma width ofabout 70 km/s, which poses a challenge for the study of the typically 20-30km/s velocity dispersion of the ionized gas in present-day disk galaxies. Inthis contribution, we present a major revision of the MaNGA data pipelinearchitecture, focusing particularly on a variety of factors impacting theeffective LSF (e.g., undersampling, spectral rectification, and data cubeconstruction). Through comparison with external assessments of the MaNGA dataprovided by substantially higher-resolution R ~ 10,000 instruments wedemonstrate that the revised MPL-10 pipeline measures the instrumental linespread function sufficiently accurately (<= 0.6% systematic, 2% random aroundthe wavelength of Halpha) that it enables reliable measurements ofastrophysical velocity dispersions sigma_Halpha ~ 20 km/s for spaxels withemission lines detected at SNR > 50. Velocity dispersions derived from [O II],Hbeta, [O III], [N II], and [S II] are consistent with those derived fromHalpha to within about 2% at sigma_Halpha > 30 km/s. Although the impact ofthese changes to the estimated LSF will be minimal at velocity dispersionsgreater than about 100 km/s, scientific results from previous data releasesthat are based on dispersions far below the instrumental resolution should bereevaulated.

SDSS-IV MaNGA: Modeling the Spectral Line Spread Function to Sub-Percent Accuracy