A pyrolysis system for evaluating a source rock sample from a subterranean reservoir and methods are described. The pyrolysis system includes a reactor vessel including a body with an open end, a cover attachable to the body, a heating system, a collector assembly. The body and the cover define a sealable chamber; a source rock sample holder sized to be received inside the sealable chamber; and a sensor system. The sensor system includes a direct sensor assembly associated with the source rock sample holder, sized to be received inside the sealable chamber, and operable to measure properties of the source rock sample in the source rock sample holder; and a pyrolysis products sensor assembly in fluid communication with the collector assembly of the reactor vessel.