A subspace infrared algorithm was a process for analyzing subspace infrared telemetry, received from spatial phenomena such as stellar clusters. The algorithm consisted of four analytical aspects, which could be regarded as four smaller algorithms. Their sequence was:
Starfleet officers had a mnemonic device for remembering the sequence: Z-G-I-F, "Zero-G Is Fun".
Tal Celes of the USS Voyager was assigned a level-3 sensor analysis of a class T cluster in 2376, involving a subspace infrared analysis. However, she had to seek William Telfer's assistance to perform it. (VOY: "Good Shepherd")