On When A Measurement Occurs in Quantum Mechanics: Is There Evidence From Correlated Events?

In his well-known gedankenexperiment involving a cat, Professor Schrödinger wrote that until the box with the cat, the radioactive material, and other elements of the experiment inside it is opened, all the elements of the experiment are described by a superposition of states in which on the one hand the cat is alive and on the other hand the cat is dead. Is it actually the case that the cat assumes a definite state of being alive or dead when the box is opened? Why should not a measurement occur earlier in the experiment before the box is opened with the decay of the radioactive material, if it occurs, that leads to the demise of the cat? Professor Schrödinger also alluded to this latter possibility in his description of his gedankenexperiment before settling on the former conclusion. The issue at hand is whether a measurement involving the cat can be made before the box is opened, and if so when? Each possibility as to when a measurement occurs involving the cat is plausible in one sense and implausible in another. The cat gedankenexperiment is a case example for the larger question in quantum mechanics of whether an experiment can be shielded from the environment with the result that a measurement event does not occur until the experiment is opened to the environment. An experiment is outlined in terms of the cat gedankenexperiment that would specifically test when a measurement event occurs through exploring correlated events to the measurement event.