Persistence in NICMOS: Results from Thermal Vacuum Data

This ISR presents an analysis of the System Level Thermal Vacuum (SLTV) persistence tests performed with NICMOS. In August 1996, persistence data was obtained as part of the SLTV, and further data were obtained in December 1996 after modifications had been made to the instrument operating procedures. The goal was to determine if NICMOS exhibits an “after-glow” or “persistence” when read out in the dark immediately after having been exposed to bright illumination; and then to characterize the behavior of such persistence. The results and analysis of the SLTV tests show that the NICMOS detectors do indeed exhibit a significant level of persistence. The level of persistence seems to decay following a power law. Furthermore, the comparison of data observed with different AUTO-FLUSH patterns verifies the efficiency of the procedure when AUTO-FLUSH is turned “on”. Quantitative analysis of the on-orbit performance of the NICMOS detectors with regard to persistence will be described in a later ISR.