An optomechanical gravimeter includes: a first and second accelerometer; and a spacer member interposed between the first accelerometer and the second accelerometer such that the first accelerometer and the second accelerometer independently include: a basal member; a test mass disposed on the basal member; a flexural member interposed between the basal member and the test mass such that the test mass is moveably disposed on the basal member via flexing of the flexural member; an armature disposed on the basal member and opposing the test mass and the flexural member such that: the armature is spaced apart from the test mass; a cavity including: a first mirror disposed on the test mass; a second mirror disposed on the armature, the spacer member providing a substantially constant distance of separation between a first measurement point of the first accelerometer and a second measurement point of the second accelerometer.
Currently many space projects require, at their core, sensors capable of measuring spurious forces acting on the spacecraft with extremely high sensitivity at ng/√Hz levels and below, particularly for high accuracy navigation and drag-free flight. NIST has developed a novel and simple concept for high-sensitivity, wide bandwidth and self-referencing optomechanical accelerometers. These devices are based on monolithic fused-silica mechanical oscillators with integrated fiber-optic Fabry-Pérot micro-cavities that yield exquisite sensitivities of the accelerometer test mass displacement. Our laboratory prototypes have demonstrated unprecedented noise floors over large bandwidths. These concepts also can be applied to measure spurious forces at lower frequencies. Thus, these products are a result of this invention: gravimeter, seismometer, gradiometer, low frequency inertial sensing, and accelerometer.
Current commercial systems of similar performance weigh several kilograms and are, at best, of the size of a backpack. The novelty of this invention lies in the realization of a highly compact and light device capable to reaching acceleration noise florrs in the order of 10-10ms-2/√Hz. The total weight of the mechanical oscillator is of the order of 30 grams, including the optical interferometer that can be constructed out of compact commercial optics yielding interferometer lengths of approximately 2 cm and below, down to lengths around 100 µm by using fiber-optic components.