Swedish-ESO Submillimetre Telescope, Radio telescope at La Silla Observatory, Chile

The Swedish-ESO Submillimetre Telescope is a radio telescope with a 15-meter diameter parabolic reflector at La Silla Observatory. It was designed to observe cosmic objects across frequencies ranging from 70 to 365 gigahertz, allowing it to study distant celestial sources in the submillimetre spectrum.

Built in 1987 as a joint project of ESO and Onsala Space Observatory, with contributions from Finland and Australia, the telescope was then the only large instrument for submillimetre astronomy in the southern hemisphere. It was decommissioned in 2003. In 2022 its relocation to the Gamsberg Nature Reserve in Namibia was announced, where it will become the Africa Millimetre Telescope.

The telescope's name links ESO with Sweden's Onsala Space Observatory, which co-built it in 1987 with contributions from Finland and Australia. Since 2022 it is being moved to the Gamsberg Nature Reserve in Namibia as the Africa Millimetre Telescope, a project of the University of Namibia in Windhoek and Radboud University in Nijmegen, with ESO and the Netherlands Research School for Astronomy involved.

The telescope stood at La Silla Observatory in Chile's Atacama region until its 2003 decommissioning. Since 2022 it has been moved to or near Gamsberg mountain in the Gamsberg Nature Reserve, Namibia, with the exact site still to be fixed. The site is not permanently open to the public, and access may require special permission.

In 2022, plans emerged to relocate the instrument to the Gamsberg Nature Reserve in Namibia, where it would become Africa's first millimetre radio telescope. This move demonstrates how scientific equipment can be repurposed and bring new observational capabilities to different regions.