Refined NISP exposure start time tag

Abstract

The goal of this document is to provide a detailed analysis of the timing inside the DPUs in order to explain the observed difference in the time-tagging between the detectors in the NISP raw science files produced during the acquisition of a single exposure and match the need to use a single time reference for all detectors in the NISP data produced by the SGS Level 1 NISP Processor software. This document will present a fine correction to the time-tag available in the NISP data products to determine with a higher accuracy the starting time of the NISP exposure, as well as the starting time of the data acquisition. These refined times are referred to the on-board time (OBT) already stored in the digital telemetry of the raw NISP science data.