NIRC2 Modes and Instrument Properties
Modes
NIRC2 has two basic modes:
- Near-IR Imaging
- Near-IR Grism Spectoscopy
Each of the basic modes can be in either Polarimetry mode, or Non-Polarimetry denoted as Standard mode.
Table 1 provides a summary of these modes and characteristics of NIRC2.
| Mode | Image or Dispersion | Chracteristics |
|---|---|---|
| Near-IR Imaging | Imaging | 0.96 - 5.0 μm Narrow: 10" x 10", 0.01"/pix Medium: 20" x 20", 0.02"/pix Wide: 40" x 40", 0.04"/pix Coronagraphy: 10 spots: 0.1" - 2" Polarimetry: linear, Wollaston prism, J, H, K, Ks, Kp, Lp, Narrow: 5" x 10" |
| Near-IR Grism Spectroscopy | Low & medium dispersion | 1 - 5.0 μm R~ 650 - 19,400 10 slits: 10 - 160 mas widths Polarimetry: linear, Wollaston prism, 1 - 2.4, 3.4 - 4.1 μm |
Instrument Properties
Table 2 shows the current general specifications for NIRC2. For more informaiton, check the Instrument and Data Format and the NIRC2 webpage.
Table2: General Specifications
| Property | Value |
|---|---|
| Input f/ ratio | f/15N |
| Wavelength range | 0.9-5.3 microns |
| Field of view | 10x10 arcsec 20x20 arcsec 40x40 arcsec |
| Pixel scale |
0.01 arcsec/pixel |
| Filters | Z, Y, J, H, K, Ks, Kp, Lw, Lp, Ms, HeIA, HeIB, Pa_gamma, Jcont, Pa_beta, Hcont, H2, CH4S, CH4L, Fe II, Kcont, CO, H2O, PAH, Br_alpha, Br_alpha_cont |
| Pupil mask | two circular fixed, four hexagonal, rotating |
| Slits | 10, 20, 30, 40, 60, 80, 120, and 160 milliarcsec |
| Coronagraphic spots | circular: 100, 150, 200, 300, 400, 600, 800, 1000, 1500, 2000 milliarcsec |
| Grisms | medres and lowres grisms (see tables 2 & 3), pupil imaging lens, and clear (imaging mode). |
| Polarimetric imaging field of view | 5x10 arcsec |
| Polarimetric imaging filters | J, H, K, Ks, Kp, Lp |
| Polarimetric spectroscopy | 1.0 - 2.4, 3.4 - 4.1 μm |
| Polarization analyzer | Wollaston prism, dual beam |
| Polarization modulator | Rotating half-wave plate; science obs. typically: 0, 45, 22.5, 67.5 deg; calibrations: 0 - 180 deg in steps of 10 or 15 deg |
| Polarization unsuitable for | High precision, less than 0.1% |
| Minimum frame time | 0.182 sec, full frame |
| Detector | 1024x1024 InSb Aladdin-3 array, 27 micron pixels 32 simultaneous outputs, grouped in 8 pixels across a row in each of 4 quadrants gain ~ 5 electrons/DN subarray capability 35 K operating temperature |
| Read noise | 38 electrons/read 11.5 DN/sqrt(N) for N samples in MCDS mode, up to N = 64, dropping more slowly beyond that until at least N = 512. (Note that N = 2 corresponds to two reads, or CDS mode.) |
| Dark current | < 0.1 electrons/pixel/sec |
| QE | 80% at 1.7 microns |
| Well depth | 100,000 electrons (at 1% linearity) |
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