Italian spring accelerometer (ISA) a high sensitive accelerometer for “BepiColombo” ESA CORNERSTONE

METRIC: A Dedicated Earth-Orbiting Spacecraft for Investigating Gravitational Physics and the Space Environment

“…It is completely passive (no instrumentation or any devices on-board); therefore, any dynamical perturbing effect acting on it should be a posteriori modeled, either analytically or numerically. In CHAMP, the effects of non-gravitational origin are directly measured by a three-axis accelerometer, made necessary by the need to remove the combined contributions of non-gravitational perturbations from the satellite-to-satellite tracking data, of which the air-drag is the dominant effect at the orbital altitude of CHAMP (this is also the choice done in the BepiColombo mission concept, again due to the complexity of the non-gravitational effects acting on the spacecraft [24][25][26]). The proposed mission retains the basic idea of having an object of a relatively simple shape, including a three-axis accelerometer package in order to overcome the problems related to modeling the non-gravitational effects and, at the same time, separating the air-drag from the solar-pressure effects, as explained later on.…”

“…a measurement of pericenter precession improved by possibly one order of magnitude, with a corresponding constraint on a Yukawa-like contribution acting at a scale comparable with the orbit semimajor axis; 2. a direct (i.e., with a single satellite) measurement of Lense-Thirring precession. The three accelerometer elements, based on the ISA (Italian Spring Accelerometer) model developed by the IAPS Experimental Gravitation Group for the BepiColombo mission [25,26], will be placed close to and aligned with the spin axis of the satellite, within the construction precision. This configuration will minimize the contribution of spurious signals due to gravitational gradients and inertial forces (see again Table 1) that are considered in the dynamics analysis shown later on.…”

Testing General Relativity with the Radio Science Experiment of the BepiColombo mission to Mercury

“…The non-gravitational effects on the Mercurycentric orbit of the spacecraft are so intense that, if not properly taken into account, they would lead to a significantly biased orbit determination. Due to the general difficulty of modeling these effects, an accelerometer (ISA-Italian Spring Accelerometer) will be placed on board the spacecraft [20]. This instrument is able to measure differential accelerations between a sensitive element and its rigid frame (cage) and thus to give accurate information on the non-gravitational accelerations.…”

“…(a) spacecraft state vector (position and velocity) at given times (Mercurycentric orbit determination); (b) spherical harmonics of the gravity field of Mercury [17] and tidal Love number k 2 [18], in order to constrain physical models of the interior of Mercury (gravimetry experiment); (c) parameters defining the model of the Mercury's rotation (rotation experiment); (d) digital calibrations for the Italian Spring Accelerometer (ISA) [19,20]; (e) state vector of Mercury and Earth-Moon Barycenter (EMB) orbits at some reference epoch, in order to improve the ephemerides (Mercury and EMB orbit determination); (f) post-Newtonian (PN) parameters [12,13,21,22], together with some related parameters, like the solar oblateness factor J 2 , the solar gravitational factor µ = GM , where G is the gravitational constant and M the Sun's mass, and its time variation, ζ = (1/µ ) dµ /dt, in order to test gravitational theories (relativity experiment).…”

The possibility of the calibration/validation of the GOCE data with the balloon-borne gradiometer

“…Its sensitivity is better than 10 −12 g/ √ Hz. The next application of it will be the ESA Beppi Colombo mission aimed to Mercury (Iafolla et al, 2000;Iafolla and Nozzoli, 2002). But another possibility of application is the construction of the gravity gradiometer.…”