Passive Wireless Sensors for Spacecraft Applications

New classes of sensors are needed on spacecraft that can be interrogated remotely using RF signals and respond with the sensor's identity as well as the environmental parameter without use of batteries. Such systems are emerging in the field of RF identification (RFID), but often lack the ability to encode a separate parameter and require the RFID tags to be mounted on an insulator-type surface. The proposed innovation does not employ the conventional 'backscatter' approach now being commercialized, which would preclude mounting the RF-powered sensor devices on metal surfaces. Passive and semiactive devices may respond on the same frequency as they are interrogated, or a separate frequency, and support frequency hopping. Advances are also needed to adapt the same to harsh air and space environments and to include encoding of sensor information for hundreds of sensors, with a total reporting time of about 1 second. Means must be incorporated to distinguish the multitude encoded responses from up to hundreds of sensors and the interrogator must not pose a health hazard to personnel.