4MOST Milestone: AIV Completion - Beginning of Systems Verification
by Harry Addison on 2025-09-25
The Cassegrain Cable Wrap being installed at the VISTA telescope. (Credit Allar Saviauk, AIP)
The Wide Field Corrector carefully being integrated into the telescope. (Credit Allar Saviauk, AIP)
On 17th September 2025, installation of 4MOST onto the VISTA telescope was completed. This marks the end of the Assembly, Integration, Verification (AIV) phase of 4MOST's journey towards observing the Universe. As Joar Brynnel remarks, "this has been a long process, with phased implementation of hardware and software on Paranal".
AIV initially began on 2nd June 2024 with installation of the Cassegrain Cable Wrap. Installation of the Wide-Field Corrector, the Guiding and Wavefront Sensor system, and the control hardware and software followed in October and November 2024, marking an end to phase 1 of AIV. AIV phase 2 began in June 2025, which saw installation of more control hardware and software, Metrology system, Calibration system, Long Fibre Feed, Fibre-Positioner (AESOP), Low-Resolution Spectrographs, and lastly the High-Resolution Spectrograph.
A spectrograph being lifted through the VISTA dome opening. (Credit Allar Saviauk, AIP)
Allar Saviauk and the AIP have done a fantastic job of documenting the AIV process, taking many pictures and producing multiple short films that give amazing insights into the work that has gone on behind the scenes:
The end of AIV means that 4MOST now enters the System Verification phase. Mark Cunningham (System Verification lead) summarised System Verification as the phase "where all the AIV work gets put to the test", with tests designed and carried out to ensure that all of the subsystems "work together as one coherent system". Some of the tests that will be conducted include fibre-to-target alignment, fibre positioning precision, checking for any stray light, and verifying the behaviour of the atmospheric dispersion corrector.
The completion of AIV serves as a reminder of the collective efforts that make projects like 4MOST possible. We wish the System Verification team good luck as they advance 4MOST closer to operations!
The hardware components of 4MOST are fully installed on the VISTA telescope. The telescope is ready to capture its first starlight! (Credit Allar Saviauk, AIP)