Abstract's details
A Comparison of the Sentinel-6B and Sentinel-6 MF Altimeter Instrument Performance
Event: 2026 Sentinel-6 Validation Team meeting
Session: S6VT plenary session
Presentation type: Poster
Sentinel-6B, launched on 16 November 2025, is the second satellite of the Copernicus Sentinel-6/Jason-CS reference-altimetry mission. Together with Sentinel-6 Michael Freilich (Sentinel-MF), it extends the long-term record of sea-surface height measurements and supports operational oceanography, climate monitoring, and sea-state observations. Several internal calibration modes are used to monitor the health and stability of the altimeter including the CAL1, CAL2 and ECHO-CAL calibration modes. The ECHO-CAL is included in the interleaved chronogram, with one ECHO-CAL per burst, and allows continuous and long-term monitoring of the altimeter.
Early analyses of the Sentinel-6B ECHO-CAL data reveals a higher gain of ~ 2 dB compared to Sentinel-6MF, indicating better radiometric performance. In addition, the Sentinel-6B ECHO-CAL shows a behavior not observed on Sentinel-6 MF. Specifically, thermistors associated with the Radio Frequency Unit (RFU) occasionally show temperature increases of about ~1^°C above the local mean over roughly 10 minutes, followed by cooling periods of about two hours. In this study, we investigate where and when these events occur and how their occurrence relates to the beta angle. The analysis shows that the events occur during low beta angles, approximately between -40^° and 35^°, consistent with colder thermal conditions in the RFU. This behavior suggests that the RFU periodically cools to the heater activation threshold, near 0^°C, after which heater activation produces the observed warming spikes. We use ocean observations and ECHO-CAL diagnostics to show that these heater cycles do not affect instrument performance. Indeed, the purpose of the ECHO-CAL is to account for thermal variations in the instrument.
Back to the list of abstractEarly analyses of the Sentinel-6B ECHO-CAL data reveals a higher gain of ~ 2 dB compared to Sentinel-6MF, indicating better radiometric performance. In addition, the Sentinel-6B ECHO-CAL shows a behavior not observed on Sentinel-6 MF. Specifically, thermistors associated with the Radio Frequency Unit (RFU) occasionally show temperature increases of about ~1^°C above the local mean over roughly 10 minutes, followed by cooling periods of about two hours. In this study, we investigate where and when these events occur and how their occurrence relates to the beta angle. The analysis shows that the events occur during low beta angles, approximately between -40^° and 35^°, consistent with colder thermal conditions in the RFU. This behavior suggests that the RFU periodically cools to the heater activation threshold, near 0^°C, after which heater activation produces the observed warming spikes. We use ocean observations and ECHO-CAL diagnostics to show that these heater cycles do not affect instrument performance. Indeed, the purpose of the ECHO-CAL is to account for thermal variations in the instrument.