A sensor system comprises a first sensor, a second sensor, and circuitry. The first sensor collects non-frozen liquid with a first collection efficiency, but does not collect frozen liquid. The second sensor collects non-frozen liquid with a second collection efficiency and also collects frozen liquid. The first collection efficiency and the second collection efficiency are substantially equivalent. The circuitry maintains the first sensor and the second sensor at a substantially constant temperature. The circuitry determines a measurement of the frozen liquid based on maintaining the first sensor and the second sensor at the substantially constant temperature. In some examples, multiple sensor systems can be used in combination to improve the accuracy of the measurement.