Istituto di Scienza e Tecnologie dell'Informazione     
Peron R., Iafolla V., Lorenzini E., Anselmo L., Pardini C., Lucchesi D., Visco M., Lefevre C., Magnafico C., Santoli F., Lucente M., Fiorenza E. Investigating fundamental physics and space environment with a dedicated Earth-orbiting spacecraft. In: COSPAR 2014 - 40th COSPAR Scientific Assembly (Moscow, Russia, 2-10 August 2014).
The near-Earth environment is a place of first choice for performing fundamental physics experiments, given its proximity to Earth and at the same time being relatively quiet dynamically for particular orbital arrangements. This environment also sees a rich phenomenology for what concerns gravitation. In fact, the general theory of relativity is an incredibly accurate description of gravitational phenomenology. However, its overall validity is being questioned by the theories that aim at reconciling it with the microscopic domain. Challenges come also from the 'mysteries' of Dark Matter and Dark Energy, though mainly at scales from the galactic up to the cosmological. It is therefore important to precisely test the consequences of the theory - as well as those of competing ones - at all the accessible scales. At the same time, the development of high-precision experimental space techniques, which are needed for tests in fundamental physics, opens the way to complementary applications. The growth of the (man-made) orbital debris population is creating problems to the future development of space. The year 2009 witnessed the first accidental collision between two satellites in orbit (Iridium and Cosmos) that led to the creation of more debris. International and national agencies are intervening by issuing and/or adopting guidelines to mitigate the growth of orbital debris. A central tenet of these guidelines requires a presence in space shorter than 25 years to satellites in low Earth orbit (LEO) after the conclusion of their operational lives. However, the determination of the natural lifetime of a satellite in LEO is very uncertain due to a large extent to the short-term and long-term variability of the atmospheric density in LEO and the comparatively low-accuracy of atmospheric density models. Many satellites orbiting in the 500-1200 km region with circular or elliptical orbits will be hard pressed to establish before flight whether or not they meet the 25-year requirement and thus they need specific arrangements for deorbiting at the end of life or they can simply rely on mother nature for reentry. The goal of this proposal is to utilize existing technology developed for acceleration measurement in space and state-of-the-art satellite tracking to precisely determine the orbit of a satellite with well-defined geometrical and mass characteristics (i.e., A/m ratio), at the same time accurately measuring over a long period of time the drag deceleration (as well as others non-gravitational effects) acting on the satellite. This will result in a virtually drag-free object that can be exploited to: 1. perform fundamental physics tests by verifying the equation of motion of a test mass in the general relativistic context and placing limits to alternative theories of gravitation; 2. improve the knowledge of selected tidal terms; 3. map, through acceleration measurements, the atmospheric density in the orbital region of interest. In its preliminary incarnation, the satellite would be cylindrical in shape and spinning about its cylinder axis that would be also orthogonal to the orbital plane. The satellite should be placed on a dawn-dusk, sun-synchronous, elliptical orbit spanning the orbital altitudes of interest (e.g., between 500 and 1200 km of altitude). The satellite should be equipped with a 3-axis accelerometer package with an acceleration resolution better than 10^-11 g (with g the acceleration at the Earth's surface). The expected measurement range is 10^-8 - 10^-11 g considering estimates of drag forces at minimum and maximum solar activity conditions in the altitude range of interest and a preliminary estimate of the satellite A/m ratio. The overall concept of the mission will be discussed, concentrating on the fundamental aspects and main scientific return. The main instrumentation to be hosted on-board the spacecraft will be then reviewed, with a focus on current and projected capabilities.
Subject Space accelerometer
Atmospheric density
Gravitational interaction
Earth satellite
70F15 Celestial mechanics

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