2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/201103A proposal is made to test Newton's inverse-square law using the perihelion shift of test masses (planets) in free fall within a spacecraft located at the Earth-Sun L2 point. Such an Artificial Planetary System In Space (APSIS) will operate in a drag-free environment with controlled experimental conditions and minimal interference from terrestrial sources of contamination. We demonstrate that such a space experiment can probe the presence of a "hidden" fifth dimension on the scale of a micron, if the perihelion shift of a "planet" can be measured to sub-arc-second accuracy. Some suggestions for spacecraft design are made.17 pages, revtex, references added. To appear in Special issue of IJMPDGeneral Relativity and Quantum CosmologyAstrophysicsHigh Energy Physics - PhenomenologySpace Physicstext