4MOST - 4-metre Multi-Object Spectroscopic Telescope
4-m Multi-Object Spectroscopic Telescope

4MOST Wide Field Corrector installed on the Cassegrain Test Stand

by Joe Liske on 2022-07-15

The Project Manager, Joar Brynnel, reports:

The 4MOST Wide Field Corrector (WFC) is a large optical system to be mounted on the VISTA telescope in front of the fiber positioner to correct the telescope beam and to create a suitable focal plane. The six large lenses in the WFC, with a diameter of almost one meter, were manufactured by KiwiStar Optics in New Zealand. They were then sent to UCL in London where the optics were installed in their mechanical structure and optically aligned.

On 28 May 2022, the WFC was delivered to the AIP in Potsdam. As the 4MOST WFC is the most expensive subsystem built and delivered by the 4MOST consortium, it was a big relief to learn that the integrated WFC had survived the transport from London to Potsdam without any damage.

On 14 July 2022, the WFC was mounted for the first time on the Cassegrain Test Stand (CTS) in the AIP integration hall. As this was the first time the WFC was handled using its dedicated lifting tool, it was an exciting operation that required quite some preparation. We are very happy to report that the handling and installation went very smoothly and according to plan. Michael Schröck, the WFC work package manager reports: “The installation of the Wide Field Corrector on the Cassegrain Integration Stand was a long awaited handling maneuver to be performed at AIP, with many first time applications of handling tools and hardware combined in one procedure. Thanks to a committed team, careful preparation, and some amount of luck the whole effort went very smoothly. The WFC was successfully installed on the test stand in two hours, verifying the fit of individual components and planned tasks during the process.”

The installation of the WFC on the CTS is an important milestone for 4MOST system integration activities, and we can now continue to integrate the Acquisition & Guiding subsystem, Focal Surface Test Tools, and the Cassegrain Cable Wrap on the CTS, which, when completed, will mark the beginning of full system integration. Fingers crossed for continued success in the integration hall!

Time lapse video of moving the WFC from its trolley to the CTS using the overhead crane. In the video: Mark Cunningham (UCL), Carlos Rodriguez, Michael Schröck, and Allar Saviauk (AIP).

The WFC (black cylinder) during integration on the CTS (white structure) by Carlos Rodriguez, Michael Schröck, and Allar Saviauk (AIP). The orange device is the dedicated WFC lifting tool.

The WFC on the CTS as seen from the front of the WFC. The WFC optics are protected by the black circular cover.