The wide variety of instrumentation available at the La Silla Paranal observatory is a key element in the ESO’s success. The current instruments provide a balanced combination of multipurpose facilities and specialised instruments to cater more specific individual science cases. On the other hand, the Adaptive Optics Facility (AOF) -comprising the Deformable Secondary Mirror (DSM), the 4-Laser Guide Star Facility (4LGSF), and post-focal Adaptive Optics sensors and devices- has significantly elevated the observational capabilities of the fourth unit telescope of the VLT (UT4).

As a by-product of these enhanced capabilities, UT4 has become extremely oversubscribed when compared with the other UTs. For a proposal to be accepted in UT4, it must have been graded much higher than in the other UTs, with even extremely good proposals being rejected.

Until very recently, relocating any instrument from UT4 to another other UT was not possible as the scientific performance of MUSE, ERIS and HAWKI is closely linked to the AOF. However, the single LGS units to be installed in UT1, UT2 and UT3 in the context of the GRAVITY+ project, together with the installation of a new DSM in one of those UTs, would enable a more balanced relocation of instruments, with an overall improvement of the scientific performance of the VLT.