Summary

4MOST is a wide-field, high-multiplex, fibre-fed, optical spectroscopic survey facility mounted on ESO's 4-m-class telescope VISTA and operated in ESO's Paranal Observatory operational environment.

4MOST is the only instrument installed at VISTA and is entirely dedicated to observations for ESO Public Surveys. Apart from the instrument itself, the facility also includes the Operations and Data Management Systems necessary for the planning, scheduling and execution of the observations, and for the reduction, analysis, validation and publication of the data and high-level data products.

4MOST features a 2.5-degree diameter field-of-view with 2436 science fibres in the focal plane. The fibres are configured by a fibre positioner based on the tilting spine principle, enabling extremely short reconfiguration times. The fibres feed three, fixed-configuration spectrographs: one third of the fibres (i.e. 812) goes to a single high-resolution spectrograph (HRS) with resolution R ≈ 18000 – 21000, while the remaining 1624 fibres feeds two low-resolution spectrographs (LRS) with resolution R ≈ 4000 – 7500. In each spectrograph the light is split into three different wavelength channels (blue, green and red) before being dispersed by VPH gratings and recorded by identical 6k × 6k E2V CCDs with low readout noise. The instrument also features a Wide Field Corrector with an Atmospheric Dispersion Corrector, an Acquisition & Guiding and Wavefront Sensor system, as well as Metrology and Calibration systems..

Detailed information about the instrument can be found in the 4MOST Consortium webpage.

Image credit: 4MOST Consortium / Roelof de Jong

Contact Information

• Please send us your comments, suggestions and report errors and inaccurate statements in the web pages and manuals.

Content of these pages

The following items are available on all the 4MOST pages, using the bar on the left.

• Overview: a short description of the instrument
• News: list of changes affecting the instrument and/or its pages.
• Instrument Description: all the important parameters of the instrument.
• Instrument Operations Team