Bruce Haines (Jet Propulsion Laboratory, California Institute of Technology, USA); Gerald Walsh (Jet Propulsion Laboratory, USA); Michael Ciminera (Jet Propulsion Laboratory, California Institute of Technology, USA); Shailen Desai (Jet Propulsion Laboratory, California Institute of Technology, USA)

In support of the long-term monitoring of the Sentinel-6 mission, JPL has developed a dual band transponder. It operates simultaneously in Ku and C bands. It allows a full calibration of range and power in both altimeter channels as well as the system time-tag bias. The transponder was first operated with the Sentinel-6 and Jason-3 missions. It has now been updated to operate with the Sentinel-3 and SWOT missions in support of inter-mission calibrations. We present the transponder instrument, information about its location, and calibration results from the above-mentioned altimetry satellites.