Integral Field Unit:
| Specification | Value |
|---|---|
| Field of View | 34″ x 35″ |
| Fiber-to-fiber pitch | 0.75″ |
| # spatial elements | 2,392 |
| # spectrographs | 8 (4 x 300 fibers + 4 x 298 fibers) |
| # dead / broken fibers | 2 (99.91% operability) |
| Focal plane fill factor | 92% |
Spectrographs
| Specification | Blue Channel | Green Channel | Red Channel |
|---|---|---|---|
| Wavelength Coverage | 3417 – 4947 A | 4634 – 7100 A | 6771 A – 1 micron |
| Resolving Power | R=1500-2500 | R=1400-2400 | R=1750-2500 |
Throughput
The following represents the team’s current best estimate including the telescope + instrument, obtained by multiplying measured efficiencies of the IFU, fiber run, and all optical glasses, coatings, and grating blazes and CCD QE measured either from the elements themselves, or witness samples. It also includes losses from focal ratio degradation, measured from sample fibers. These pre-ship estimates will be replaced by measured efficiencies on the sky following instrument commissioning.
Spectral Resolution
From the table above, one can see that LLAMAS’ spectral resolution varies across its bandpass. This is a property of the VPH gratings and is fixed / not configurable. There is some variation in R between spectrographs and fibers, but overall the performance is fairly uniform across the full instrument. The figures below illustrate how R varies with wavelength within each spectral channel. Gray lines show measurements for individual fibers, and the blue, green and red dashed lines indicate averages for the blue, green, and red spectral channels, respectively.
