The conceptual design of the instrument is driven by the WEAVE science requirements, as defined by the Science Team, and translated to technical requirements by the Project and Instrument Scientists. At the time of writing the requirements call for a dual-beam spectrograph with the following characteristics:
| Specification | Requirement | Goal |
|---|---|---|
| Field of view diameter | 2 degrees | 2 degrees |
| MOS multiplex | 800 | 1000 |
| Atmospheric dispersion compensation | 0.4-1.0 µm, 50oZD | 0.37-1.0 µm, 60oZD |
| MOS fibre aperture | >=1.2" | 1.5" |
| Open shutter efficiency (1 hour observations) | 70% | 90% |
| Wavelength coverage | 400-950nm | 370-1000nm |
| Spectral resolution (full simultaneous coverage) | 5000 | 5000 |
| Spectral resolution (reduced coverage) | 20000 | 20000 |
| Stray light as function of faintest target | <1% | |
| Blue system efficiency | 20% | 25% |
| Red system efficiency | 25% | 30% |
| Multi-IFU multiplex | 10 | 30 |
| Multi-IFU FOV | 9" x 9" | 9" x 12" |
| Multi-IFU spaxel size | 0.8" | >1.2" |
| Single IFU FOV | 3' x 3' | |
| Single IFU spaxel size | 2.5" | Inner 1", outer 2.5" |