Effect of NOAA satellite orbital drift on AVHRR-derived phenological metrics

•Solar zenith angle data associated with the 1-km resolution AVHRR vegetation index time series (1989–2014) were analyzed for the conterminous United States.•NOAA satellite orbital drift caused increasing solar zenith angle in AVHRR observations for each satellite mission.•Statistically significant correlations between solar zenith angle and AVHRR phenological metrics were found over 4.2–20.3% of the study area.•Eliminating the years with high solar zenith angle reduced the influence of orbital drift on AVHRR phenological metrics.