GRAVITY+ is an upgrade project of the existing GRAVITY instrument at Paranal with new Adaptive Optics systems and an upgrade of the VLT infrastructure to accommodate one laser on each UT to boost the performance. The project incorporates the upgrade of existing CIAO and MACAO AO systems with bigger DM, faster WFS and more powerful RTC. One LGS system will be installed on each UT as an addition to these two SCAO systems upgrade to increase the sky coverage.

The new RTC is based on SPARTA Upgrade, where the co-processing cluster SW is based on old SPARTA legacy SW, but the HRTC part is based on new upgraded version of SPARTA RTC box HW and updated version of Platform SW. SPARTA upgrade for GRAVITY+ accommodate different type of Ethernet based I/O interfaces like GigE for WFS cameras, custom UDP based protocol for ALPAO DM, TCP IP based protocol for M2 fast tip-tilt offload interface and MUDPI protocol for laser jitter actuators. sFPDP interface is also maintained for CIAO SAPHIRA WFS by using new PCIe cards from SPARTA upgrade. The core hard real-time control SW is partially based on SPARTA Upgrade components, but some control blocks are specifically designed and implemented for GRAVITY+ RTC like collaborative control for fast TT offload, anti-windup filtering, chopping etc. The soft real-time co-processing cluster SW is partially based on the experience from SPARTA for ERIS, but most of the core algorithm are redesigned and implemented particularly for GRAVITY+.

Roderick Dembet, Observatoire de Paris - LESIA