In-flight pixel degradation of the Sentinel 5 Precursor TROPOMI-SWIR HgCdTe detector

TL;DR

This study investigates the in-orbit degradation and recovery of the Sentinel-5 Precursor TROPOMI-SWIR HgCdTe detector over five years, showing most pixels recover spontaneously and the detector remains within operational specifications.

Contribution

It provides the first detailed analysis of in-orbit pixel degradation and recovery dynamics for the TROPOMI-SWIR HgCdTe detector, informing future space instrument design.

Findings

95% of damaged pixels recover within days to months

No new damage clusters observed over five years

Detector performance remains within specifications despite radiation exposure

Abstract

The TROPOMI-SWIR HgCdTe detector on the Sentinel-5 Precursor mission has been performing in-orbit measurements of molecular absorption in Earth's atmosphere since its launch in October 2017. In its polar orbit the detector is continuously exposed to potentially harmful energetic particles. Calibration measurements taken during the eclipse are used to inspect the performance of this detector. This paper explores the in-orbit degradation of the HgCdTe detector. After five years, the detector is still performing within specifications, even though pixels are continuously hit by cosmic radiation. The bulk of the impacts have no lasting effects, and most of the damaged pixels (95%) appear to recover on the order of a few days to several months, attributed to a slow spontaneous recovery of defects in the HgCdTe detector material. This is observed at the operational temperature of 140 K. The distribution of the observed recovery times has a mean around nine days with a significant tail towards several months. Pixels that have degraded have a significant probability to degrade again. The location of faulty pixels follows a Poissonian distribution across the detector. No new clusters have appeared, revealing that impacts are dominated by relatively low energetic protons and electrons. Due to the observed spontaneous recovery of pixels, the fraction of pixels meeting all quality requirements in the nominal operations phase has always been over 98.7%. The observed performance of the TROPOMI-SWIR detector in-flight impacts selection criteria of HgCdTe detectors for future space instrumentation.