NICER observation list: Target ID 756602

Most blazars are studied only during large outbursts, in response to activity observed by monitoring instruments. This approach reveals little about the standard behavior of a source, which requires consistent, repeated observations over a period of time, independent of the variability or flux state of the target. Mrk 421 is the perfect candidate for such studies. Daily NICER observations can provide unprecedented data to probe the particle acceleration and photon emission processes in this iconic TeV-emitting HBL, both on their own and in the rich multiwavelength context provided by other observations. NICER's large effective area and quick repointing capability make it ideally suited to acquire high-quality spectra of Mrk 421 on a daily basis with a modest investment of observing time.