4MOST installation on VISTA

by Harry Addison on 2025-09-12

In June 2025 the last subsystems of 4MOST were shipped from the AIP, Germany, to Paranal, Chile. We are glad to report that all of the shipments arrived safely at the VISTA telescope and that 4MOST in its entirety is now at Paranal.

With the arrival of the final shipments at Paranal, installation of the various subsystems has been carried out by the many specialist teams. The metrology system that monitors the fibre spine positions was installed and calibrated using the focal surface test tool. The test tool was then removed from the focal plane and the team from AAO reintegrated, tested, and installed the fibre positioner onto the telescope. A team from MPIA then installed 4MOST's electronic cabinets and wiring for all of the systems. Finally, the cassegrain cable wrap and the almost 2500 fibres were installed, with the fibres being connected to the fibre positioner.

The recent shipments also included the two low resolution and the high resolution spectrographs. As these were dismantled for shipping, they have been reassembled and aligned in the New Integration Hall at Paranal Base Camp by teams from CRAL and AIP. The two low resolution spectrographs have been reassembled and tested, meeting all of their specification requirements and even exceeding many. On the 5th and 7th of September the low resolution spectrographs were craned into the VISTA dome and installed side by side under the main telescope platform. The high resolution spectrograph currently remains in the New Integration Hall for final checks before being installed on VISTA in the coming weeks.

To demonstrate the hard work that has been taking place at Paranal, Allar Saviauk has produced a short film documenting the recent installation work. The film can be viewed at https://cloud.aip.de/index.php/s/3GF8B3jQiKbTbec.

With the installation of 4MOST nearing completion, we now look forward towards celebrating everyone's hard work with 4MOST's first light!