Different time allocation committees (TACs) award the telescope time available at each installation. Seventy-five per cent of this time is generally allocated by the national community or consortia of the countries that own or operate the telescope. Five per cent is allocated by the International Scientific Committee (CCI) to large international teams carrying out major observational projects, and the remaining twenty percent is allocated to Spanish researchers by a TAC managed by the IAC. This time is the principal scientific return that the host country receives under the Agreements on Cooperation in Astrophysics and are therefore the most productive and lowest cost terrestrial scientific resources available to Spanish astrophysicists. The telescope time is the main service provided by the OT and ORM, as well as providing a first-class platform for installing, testing and operating state-of-the-art infrastructures for astrophysical research.

In representation of the Spanish State, the Instituto de Astrofísica de Canarias (IAC) is responsible for the administration of this Singular Scientific and Technical Infrastructure (ICTS). The IAC provides both basic and advanced infrastructures to the international organizations, as well as managing the aforementioned 20% Spanish time. As a research centre of international prestige, the IAC contributes greatly to the scientific exploitation of these facilities.