Here are the latest specifications on NIRES. They will be updated as information becomes available when the instrument is commissioned.

Location Right Bent Cassegrain (RBC) port on Keck 2
Input f/ ratio f/15 nominal (f/16.6 cold circular pupil mask to inscribe Keck entrance pupil)
Wavelength range and Resolution

Fixed configuration, simultaneous J, H and K band spectra in five orders from 0.94 to 2.45 µ. Orders 3 through 7 with overlap, the only gap is between 1.85 - 1.88 µm, a region of poor atmospheric transmission.


The mean resolution is 2700. As expected the resolution changes with order and wavelength.

Field of view Slit viewer: 2.1 x 2.1 arcmin (K' only)
Optical guider: 1.8 x 1.8 arcmin
Guiding The main guider for NIRES is an off-axis visual guider. The K band slit-viewing camera can be used as a backup guider.
Pixel scale Slit viewer: 0.123 arcsec/pixel. Spectrometer: 0.15 arcsec/pixel
Filters K' only for slit viewing camera
Slit Fixed 0.55” by 18”
Sensitivity Please see the sensitivity section
Minimum frame time 1.48 seconds for the H2RG

Spectrograph - HgCdTe, 2024 x 2048 (Hawaii 2RG)
Slit viewer - HgCdTe, 1024 x 1024 (Hawaii 1)
Operating temperature approximately 77° K

Detector electronics

SDSU-III, mounted near instrument, fiber connection to a target computer (Sun), similar to OSIRIS detector server.

H2RG Read noise

15 electrons per CDS read
<5 electrons for MCDS with 16 reads

H2RG Dark current Internal background of 0.13 electrons/pixel/sec
H2RG Gain 3.8 e-/ADU
H2RG Well depth 150000 electrons
H2RG Persistence Significant persistence is present for some 10 minutes if the maximum ADUs are above 4000.
Construction Self-contained instrument with no moving parts except for the active flexure correction system; vacuum dewar, liquid nitrogen cooled with an internal cryogen tank.

Liquid nitrogen held in instrument; minimum hold time 1 day, goal ~ 3+ days.

Size & Weight Approximately 50 inches long and 800 lbs.

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