This table records high-level information for the observations obtained with NICER (Neutron star Interior Composition ExploreR) and provides access to the NICER data archive. NICER is a NASA Explorer program Mission of Opportunity dedicated to the study of the neutron stars, exploring the exotic states of matter where density and pressure are higher than in atomic nuclei. NICER instrument is a payload aboard the International Space Station (ISS). It was launched on 3 June 2017 on a SpaceX Falcon 9 rocket and placed on the ISS. Normal operation started on 17 July 2017 after a commission phase to test the system and perform initial calibration. NICER's X-ray Timing Instrument (XTI) consists of an aligned collection of 56 X-ray "concentrator" optics (XRC) and silicon drift detector (SDD) pairs working in the energy range of 0.2-12 keV. Each XRC collects X-rays over a large geometric area from a roughly 30 arcmin<sup>2</sup> region of the sky and focuses them onto a small SDD. The SDD detects individual photons, recording both energies (with a 3% energy resolution at 6 keV) and high precision times (with 100 nanoseconds RMS relative to Universal Time). During one day of operation, NICER monitors several sources. For each observed source the data are divided into intervals of one day and labeled with a sequence number. This database table contains one record for each sequence number and includes parameters related to the observation. This contents of this database table are generated at the NICER Science and Mission Operations Center (SMOC) and updated regularly with new observations. Note that some fields have been added and are populated by the HEASARC. This is a service provided by NASA HEASARC .
