A space mission is described which consists of a rigid spin-axis-stabilised spacecraft with two small, high-density masses free-falling inside. The gravitational attraction of the masses dominates all perturbations, providing a miniature 'planet-satellite' system that can only be realised in space. Unlike any celestial two-body system, the masses can be weighed on Earth before launch. Thus, monitoring their motion by means of an inward-looking tracking camera allows the value of the universal constant of gravity, G, to be determined. A careful analysis of all perturbing forces shows that G can be measured at least to 1 part in 10-5, and perhaps even somewhat better. In addition to the measurement of G, the mission would provide, at no extra cost, a new-concept (optical) drag-free satellite, to the level of 10(-10) cm/s2 or better. Being subject solely to gravitational forces, the spacecraft can provide valuable information on the geopotential and its variation with time. If an onboard accelerometer were added, it would be possible to calibrate it. Measurements of temporal charges in the solar constant, as well as information on other transient phenomena can also be obtained. The main appeal of this mission is, nevertheless, the direct way in which it can measure the oldest and least-well-determined physical constant.
THE NEWTON MISSION - A PROPOSED MANMADE PLANETARY SYSTEM IN SPACE TO MEASURE THE GRAVITATIONAL CONSTANT
NOBILI, ANNA MARIA;MILANI COMPARETTI, ANDREA;
1990-01-01
Abstract
A space mission is described which consists of a rigid spin-axis-stabilised spacecraft with two small, high-density masses free-falling inside. The gravitational attraction of the masses dominates all perturbations, providing a miniature 'planet-satellite' system that can only be realised in space. Unlike any celestial two-body system, the masses can be weighed on Earth before launch. Thus, monitoring their motion by means of an inward-looking tracking camera allows the value of the universal constant of gravity, G, to be determined. A careful analysis of all perturbing forces shows that G can be measured at least to 1 part in 10-5, and perhaps even somewhat better. In addition to the measurement of G, the mission would provide, at no extra cost, a new-concept (optical) drag-free satellite, to the level of 10(-10) cm/s2 or better. Being subject solely to gravitational forces, the spacecraft can provide valuable information on the geopotential and its variation with time. If an onboard accelerometer were added, it would be possible to calibrate it. Measurements of temporal charges in the solar constant, as well as information on other transient phenomena can also be obtained. The main appeal of this mission is, nevertheless, the direct way in which it can measure the oldest and least-well-determined physical constant.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
