1. A method comprising: capturing a signal from a shielded infrared sensor that is blocked from receiving infrared radiation from a scene; capturing a signal from an unshielded infrared sensor configured to receive the infrared radiation from the scene, wherein the shielded infrared sensor and the unshielded infrared sensor are part of an infrared sensor assembly; determining a temperature dependent infrared radiation contribution from a shield structure of the infrared sensor assembly incident on the shielded infrared sensor; determining an average thermographic offset reference based on the captured signal of the shielded infrared sensor reduced by the determined infrared radiation contribution; determining an absolute radiometric value, corresponding to the infrared radiation received from the scene by the unshielded infrared sensor, based on the average thermographic offset reference and the captured signal of the unshielded infrared sensor; and wherein the absolute radiometric value is determined without the use of a shutter.