In view of the request by the Federal Republic of Germany to join the agreement on cooperation in astrophysical research and the protocol between the governments of the Kingdom of Spain, the Kingdom of Denmark, the United Kingdom of Great Britain and Northern Ireland and the Kingdom of Sweden, signed in Santa Cruz de La Palma on the 26th of May of 1979, and published in the official State bulletin no.161 on the 6th of July of 1979, the signatory bodies consider that it is necessary to introduce an addendum to the protocol on co-operation in astrophysical research in the following terms: The aforementioned protocol referring exclusively to the Observatory at Roque de los Muchachos shall be extended to include the Observatory of Teide in accordance with the provisions of the Protocol with the exception of the modifications introduced by the present Addendum.

The Government of the Kingdom of Spain, the Government of the Kingdom of Denmark, the Government of the United Kingdom of Great Britain and Northern Ireland and the Government of the Kingdom of Sweden; Desiring to encourage relations of scientific cooperation between these countries; Aware of the importance of this cooperation for the better development of relations between them; Taking into account their common interest in encouraging research in the field of Astrophysics; Recognising the benefits which may accrue to science from close international cooperation; Recognising that there are in Spain, especially in Tenerife and La Palma, areas providing unique conditions for astronomical observation; Bearing in mind the great interest shown by various European scientific Institutions in the installation of powerful telescopes on the Canary Islands; Considering the decision by the Government of the Kingdom of Spain to make the observatories of the Astrophysical Institute of the Canary Islands available to the international scientific community on the Canary Islands and, in compliance with that decision, to authorise the use of such observatories by the scientific Institutions of the Contracting Parties for the purpose of astrophysical research on the terms laid down in this Agreement and provided that the Signatory Bodies named in Article 3 conclude a Protocol with the Higher Council of Scientific Research of Spain (hereinafter referred to as the CSIC);