Prototype Testing of the AMR-CR Instrument: Drivers, Implementation, and Results

The CRISTAL mission will perform critical cryosphere science and is the next evolution for ocean topography measurements in the polar regions. The instrument suite on CRISTAL includes the Interferometric Radar Altimeter for Ice and Snow (IRIS) and the Advanced Microwave Radiometer for CRISTAL (AMR-CR), which will support the secondary ocean altimetry mission objective by providing correction for the radar path delay due to atmospheric water vapor. The AMR-CR instrument is a 6-channel radiometer with significant heritage from former AMR missions, such as those flown on Sentinel-6 and Jason-3. Many elements of the instrument design were inherited from previous missions, including the RF electronics, structural design, and calibration system, but some updates were made to the design to modernize the electronics, software, and programmable logic in the instrument. Merging the updated electronics with the inherited framework posed unique challenges and introduced risk of self-compatibility or performance issues arising post instrument integration, at which point issues are more difficult to correct and have greater impact to cost and schedule. In response to these risks, the project pursued a prototype test campaign prior to the start of flight hardware integration. This paper describes specific differences, both internal and external, between CRISTAL AMR-CR and Sentinel-6 AMR-C that led to the selection and execution of two high priority test cases. The test results validated the functionality of the updated electronics and indicated their compatibility with the inherited receivers and spacecraft interfaces.