ERIS, first generation becoming second generation, or re-vitalizing an AO instrument

Within the VLT instrumentation program, the second generation instrument ERIS (Enhanced Resolution Imager and Spectrograph) combines two key scientifically successful elements of the VLT first generation instrumentation program: It consists of a full renovation of the integral field spectrograph SPIFFI and a new near-IR camera NIX, implementing the most scientifically important imaging modes offered so far by NACO (imaging in the J to M bands, astrometry, Sparse Aperture Masking and Apodizing Phase Plate (APP) coronagraphy). Both diffraction limited sub-systems of ERIS make use of the latest AO technologies with the newly installed AOF (AO Facility) Deformable Secondary Mirror with 1170 actuators and a new laser guide star system. We will describe the changes that will be implemented, give a summary of what SINFONI is currently achieving, and present what to expect from the performance upgrade. With instruments becoming more complex and therefore increasing development times, we describe the challenges to improve image quality, spectral and spatial resolution on the same focus of a VLT UT, which could become valuable lessons for the extension of the life of actual instruments and of future ones. We will address the impact of the aging of the instrument and what critical parts to consider in the design in view of future upgrades, to possibly extend the performances, capabilities and lifetime at lower development costs.