The blue LED inside the radome got fainter as the alkaline AA cells faded away, but remained visible in a dark room until the discrete LM3909 circuitry stopped oscillating with the battery at 1.0 V. One of the cells had flatlined, with the other supplying what little current was needed.
The circuitry restarted with a pair of weak alkalines applying 2.4 V across the bus bars:
The LED waveform shows it needs about 2 V:
It’s barely visible in normal room light and strikingly bright at night.
The Smell of Molten Projects in the Morning 
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