The conceptual design of the instrument was driven by the WEAVE science requirements, as defined by the Science Team, and translated to technical requirements by the Project and Instrument Scientists. The following table summarises the instrument characteristics:
|Field of view diameter||2 degrees||2 degrees||2 degrees|
|Atmospheric dispersion compensation||0.4-1.0 µm, 50oZD||0.37-1.0 µm, 60oZD||0.37-1.0 µm, 60oZD|
|MOS fibre aperture||>=1.2"||1.5"||1.3"|
|Open shutter efficiency (1 hour observations)||70%||90%|
|Spectral resolution (full simultaneous coverage)||5000||5000||5000|
|Spectral resolution (reduced coverage)||20000||20000||20000|
|Stray light as function of faintest target||<1%|
|Blue system efficiency||20%||25%||25%|
|Red system efficiency||25%||30%||30%|
|Multi-IFU FOV||9" x 9"||9" x 12"||9" hex|
|Multi-IFU spaxel size||0.8"||>1.2"||1.3"|
|Single IFU FOV||3' x 3'||1.5'|
|Single IFU spaxel size||2.5"||Inner 1", outer 2.5"||2.6"|
*The focal plane of each camera is occupied by two e2V CCD231-C6 CCDs (6kx6k format). The Useful spectrograph focal plane is 8k spectral x 6k spatial. This implies a small gap between the two CCDs. At the central slit position, these gaps span 549.1-553.9nm and 759.0-766.9nm in the low resolution mode and 452.5-453.6nm ; 530.2-531.5nm and 641.2-643.1nm in the high resolution modes. The spectrograph slit is curved to match the low resolution gratings, leaving a residual curvature in the high resolution mode of around 3.5nm shift (~350 pixels) between the central and extreme fibres.
The philosophy behind the construction of WEAVE is to keep it simple but effective. Thus the design exploits the use of COTS (Commercial Off-The Shelf) components which not only reduces project costs and risks but provides an attractive solution for maintaining the instrument throughout its lifecycle.
The Instrument Block Diagram
The Instrument Block Diagram provides an high-level overview of the arrangement of the systems that comprise WEAVE. For readability, detailed component information is not represented here but the flow of data and signals are shown.
The WEAVE Instrument System
The WEAVE instrument consists of nine technical systems each of which is designed to deliver a specific functionality and provide appropriate interfaces to adjacent systems. The following table contains links to these technical systems:
|Two-degree Prime Focus System||This system consists of the Prime Focus Corrector which includes the ADC, the instrument rotator and the focussing mechanism.|
|Fibre Positioner System||This system consists of the pick-and-place fibre positioner and it's software, the tumbler, the large IFU head and part of the acquisition and guidance subsystem. in addition to this, the Configure Tool is also part of this system.|
|Fibre Systems||This system consists of the MOS fibres, the IFU fibres and the guide fibres|
|Spectrograph System||This system consists of the spectrograph and the science detectors.|
|Observatory Control System|
This system consists of the software for controlling all aspects of the instrument, with the exception of the Fibre Positioner, and automating the observations.
|Core Processing System||This system consists of the quality control of the science data, the operational repository and full image processing and spectral extraction.|
|WHT support facilities||This system includes all the modifications that are required at the telescope to accept the instrument and calibration of the focal plane.|
|Advanced Processing System||This system consists of the software required to carry out high-level science analysis.|
|WEAVE Archive System||This system consists of the data archive.|