The THD instrument. Most of what you see is the voltage regulator and conversion electronics; the sensor itself would attach to the small black socket in the middle.

Tunneling Horizon Detector

The Tunneling Horizon Detectors (THD) are the paying payload for SAPPHIRE. They are built around a micromachined sensor from JPL. Extensive documentation is available at the SMSSL site.

SAPPHIRE includes the readings of the two THD's among the telemetry points, reading the analog signal from the THD's, passing them through an AtoD converter, and then storing the information.

More information is available about the THDs:

Quick Reference Sheet
Device Status
Experimental Data

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