A Class-1 probe is a type of probe used by Starfleet ships in the late 24th century.
In 2365, the USS Enterprise-D launched a probe of this type with a full sensor platform to study a hole in space, created by Nagilum. (TNG: "Where Silence Has Lease")
Later that year on Drema IV, an Enterprise survey team suggested that harmonic vibrations emitted by class-1 probes fitted with resonators fired into the planet would shatter the planet's dilithium lattices, and thus alleviate the tectonic stresses that were tearing the planet apart. The plan was a success and the planet was saved from destruction. (TNG: "Pen Pals")
A class-1 probe, with sensor set to maximum scan and modified for planetary probe, was launched into the Romulan Neutral Zone to Nelvana III to scan for signs of a Romulan base on the planet. The probe went into orbit and began to pick up low level subspace radio emissions (TNG: "The Defector")
In 2366, the Enterprise launched a probe of this type to study a closing temporal anomaly before heading to Archer IV. (TNG: "Yesterday's Enterprise")