NICER observation list: Target ID 357801

Cir X-1 has established its unique position in the binary evolution as the youngest known star and compact object binary. The system is also known for its peculiar X-ray variability, which needs to be physically understood for deciphering information that the system remembers since its last SN explosion. We focus on the X-ray variability within an orbital cycle, which is made by an interplay of a few ruling physics. Spectroscopic monitor at a high cadence over an entire orbital phase is a key to disentangling these interplaying physics and putting the observed complexity into a physical context. We propose approximately 100 snapshots within a 16.6~day period with NICER, which is uniquely suited for its operational flexibility, a large effective area, and a moderate energy resolution.