Italian Spring Accelerometer (ISA): A fundamental support to BepiColombo Radio Science Experiments

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.…”

“…In particular, they could be attainable with an adaptation of the ISA BepiColombo accelerometer to the proposed mission. Very important in this respect is the fact that METRIC would offer a stable environment for the instruments it will host; indeed, a relevant part of the accelerometer error budget in that case is given by spurious signals coming from the on-board environment itself (see, e.g., [26,51]). …”

The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets

“…Of primary importance in exploiting the information content of these data will be a proper modelling of spacecraft dynamics. Combining radio-science and acceleration measurements not only improves the precision and quality of spacecraft navigation but also allows us to remove, as fully as possible, the systematic effects of non-gravitational forces acting on the spacecraft (Iafolla et al, 2010). These scientific goals are intimately connected to the planetary science goals since gravitation is directly connected to planetary ephemeris (Fienga et al, 2010) as well as to the origins of the Solar System (Blanc et al, 2005).…”

The comparative exploration of the ice giant planets with twin spacecraft: Unveiling the history of our Solar System

“…Fundamental to this objective is a proper modelling of the spacecraft dynamics, both gravitational and non-gravitational. This could be non-trivial in case of a complex spacecraft (the ideal would be a test mass) and -in selected cases -could require also the use of an on-board accelerometer (Iafolla et al, 2010). In the case of Uranus, measurements of the precession of its elliptical rings should add to the list of observables.…”