A method of operation in an interrogation system operable to interrogate wireless transponders physically associated with respective specimen containers, the wireless transponders and the respective specimen containers stored in a cryogenic environment, the interrogation system comprising: a plurality of antennas spatially arrayed in an array of antennas, the array of antennas having a set of one or more dimensions; at least one radio communicatively coupled to drive the antennas to emit interrogation signals to interrogate the wireless transponders in the cryogenic environment and to receive response signals from any of the wireless transponders in a range of one or more of the antennas; and a processor-based control system communicatively coupled to the at least one radio, the method comprising: for each response signal received in response to a given interrogation, determining which response signal was returned from one of the wireless transponders that is a closest wireless transponder to the antenna that emitted the respective interrogation signal to which the wireless transponders are responding, and storing in at least one data structure a mapping that relates an identity of at least one of the wireless transponders and a respective spatial position in an array of positions in a cassette (202, 302), the array of positions in the cassette (202, 302) having a set of one or more dimensions and the set of one or more dimensions of the array of positions in the cassette (202, 302) being equal to or less than corresponding dimensions of the set of one or more dimensions of the array of antennas, characterized in that determining which response signal was returned from one of the wireless transponders that is the closest wireless transponder to the antenna that emitted the respective interrogation signal to which the wireless transponders are responding includes: - for each response signal received in response to a given interrogation, normalizing by at least one of the processor-based control system or the at least one radio a respective received signal strength indicator (RSSI) value that indicates a received signal strength of the response signal to account for any automatic gain adjustment introduced by the at least one radio, and - for each interrogation, determining by the processor-based control system which of the respective normalized RSSI values for the response signals received in response to a given interrogation has the largest absolute value. for each response signal received in response to a given interrogation, determining which response signal was returned from one of the wireless transponders that is a closest wireless transponder to the antenna that emitted the respective interrogation signal to which the wireless transponders are responding, and storing in at least one data structure a mapping that relates an identity of at least one of the wireless transponders and a respective spatial position in an array of positions in a cassette (202, 302), the array of positions in the cassette (202, 302) having a set of one or more dimensions and the set of one or more dimensions of the array of positions in the cassette (202, 302) being equal to or less than corresponding dimensions of the set of one or more dimensions of the array of antennas, characterized in that determining which response signal was returned from one of the wireless transponders that is the closest wireless transponder to the antenna that emitted the respective interrogation signal to which the wireless transponders are responding includes: - for each response signal received in response to a given interrogation, normalizing by at least one of the processor-based control system or the at least one radio a respective received signal strength indicator (RSSI) value that indicates a received signal strength of the response signal to account for any automatic gain adjustment introduced by the at least one radio, and - for each interrogation, determining by the processor-based control system which of the respective normalized RSSI values for the response signals received in response to a given interrogation has the largest absolute value. - for each response signal received in response to a given interrogation, normalizing by at least one of the processor-based control system or the at least one radio a respective received signal strength indicator (RSSI) value that indicates a received signal strength of the response signal to account for any automatic gain adjustment introduced by the at least one radio, and - for each interrogation, determining by the processor-based control system which of the respective normalized RSSI values for the response signals received in response to a given interrogation has the largest absolute value.