TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The tracking apparatus (A1) further comprises a contact region having a boundary in contact with at least one contact surface, where the support structure is mounted on the support surface at the contact surfaces, and the overturn axis is coincident with at least one point along the boundary of the contact region. In the tracking apparatus (A1): the tracking assembly is constructed of reinforced concrete; the tracking assembly comprises a tilt structure rotatably coupled to the support structure, where the tilt structure is configured to tilt about the first axis, and the first axis comprises a horizontal tilt axis, or comprises an azimuth structure (34) coupled to the support structure, where the azimuth structure is configured to rotate about the first axis, and the first axis comprises an azimuth axis perpendicular to the support surface; and the tracking assembly further comprises a roll structure rotatably coupled between the tilt structure and the payload assembly, where the roll structure is configured to pivot about the second axis, and the second axis comprises a roll axis perpendicular to the tilt axis, or further comprises an elevation structure (36) rotatably coupled to the azimuth structure, where the payload assembly is configured to pivot about the second axis, and the second axis comprises a pivot axis transverse to the azimuth axis. The tracking apparatus (A2) further comprises: a support structure mounted to a support surface and having a fifth center of mass, where the tracking assembly is mounted on the support structure and the support structure comprises peripheral edges defining overturn axes of the tracking apparatus; an azimuth actuator coupled to the tracking assembly, where the azimuth actuator is configured to rotate the tracking assembly about the azimuth axis; and a pivot actuator coupling the tracking assembly and the payload assembly, where the pivot actuator is configured to rotate the payload assembly about the pivot axis relative to the tracking assembly. In the tracking apparatus (A2): the tracking assembly comprises an azimuth structure having a third center of mass and an elevation structure having a fourth center of mass, where the third center of mass and the fourth center of mass are at or near the azimuth axis, and the azimuth structure and the elevation structure are constructed of reinforced concrete; a net gravitational moment results from gravitational forces acting on the first center of mass, the second center of mass, and the fifth center of mass, where the magnitude of a contribution to the net gravitational moment from the first center of mass and the second center of mass is greater than the magnitude of a contribution from the fifth center of mass; a distance between the first center of mass or the second center of mass and any possible overturn axis is about the same; the net gravitational moment is greater than and opposite a net wind moment, where the net wind moment results from a wind pressure profile acting on the tracking apparatus; and the payload assembly comprises at least one photovoltaic module. The support structure has a first center of mass, the concrete tilt structure has a second center of mass, and the payload assembly has a third center of mass, where a magnitude of a net contribution to a net gravitational moment about overturn axes of the tilt-roll tracking apparatus from the second center of mass and the third center of mass is greater than a magnitude of a contribution to the net gravitational moment about the overturn axes from the first center of mass.