Adaptive optics for diffraction-limited infrared imaging with 8-m telescopes

Atmospheric Parameters for the MK and the MMK Turbulence Models at λ = 0.5, λ = 1.6, λ = 2.2 μm

Tilt Errors from the Combined Effects of Temporal Decorrelation and Measurement Noisea

a The table gives the integration length that is necessary to balance decorrelation and measurement noise. The corresponding combined error, equal to [(σ_θ^noise)² + (σ_θ^time)²]^1/2, is expressed in rms motion (arcsec), and the corresponding Strehl ratio is computed from Eq. (9) with D = 8 m. The calculation is for different star flux levels, assuming a constant background sky flux of 9000 [(photon/s)/m²]/arcsec² incident at the telescope. The quad-cell pixel size is 0.15 arcsec with readout noise of 5 electrons rms, and the overall system quantum efficiency is 40%.

Error Sources for Correcting the High-Order Wave-Front across an 8-m Telescope at λ = 1.6 μm and λ = 2.2 μma

a The value of σ_ϕ^rec assumes a 1.5-W sodium laser for λ = 2.2 μm and a 3-W laser for λ = 1.6 μm.

Contributions to the Total Strehl Ratio for the H (λ = 1.6 μm) and the K (λ = 2.2 μm) Wave Bandsa

a The high-order Strehl ratios S_ϕ, are taken from Table 3. The tilt Strehl ratios S_θ are appropriate if one is using a field star (50%) or a faint star that is coincident with the laser beacon (80%) as analyzed in Section 5. The total Strehl ratios are given by S = S_θS_ϕ. The probabilities for finding at least one sufficiently bright field star within the required angle to give a 50% tilt Strehil ratio are given for the galactic pole (P_pole) and for 30° galactic latitude (P_30°).

Table 1

Atmospheric Parameters for the MK and the MMK Turbulence Models at λ = 0.5, λ = 1.6, λ = 2.2 μm

Table 2

Tilt Errors from the Combined Effects of Temporal Decorrelation and Measurement Noisea

a The table gives the integration length that is necessary to balance decorrelation and measurement noise. The corresponding combined error, equal to [(σ_θ^noise)² + (σ_θ^time)²]^1/2, is expressed in rms motion (arcsec), and the corresponding Strehl ratio is computed from Eq. (9) with D = 8 m. The calculation is for different star flux levels, assuming a constant background sky flux of 9000 [(photon/s)/m²]/arcsec² incident at the telescope. The quad-cell pixel size is 0.15 arcsec with readout noise of 5 electrons rms, and the overall system quantum efficiency is 40%.

Table 3

Error Sources for Correcting the High-Order Wave-Front across an 8-m Telescope at λ = 1.6 μm and λ = 2.2 μma

a The value of σ_ϕ^rec assumes a 1.5-W sodium laser for λ = 2.2 μm and a 3-W laser for λ = 1.6 μm.

Table 4

Contributions to the Total Strehl Ratio for the H (λ = 1.6 μm) and the K (λ = 2.2 μm) Wave Bandsa

a The high-order Strehl ratios S_ϕ, are taken from Table 3. The tilt Strehl ratios S_θ are appropriate if one is using a field star (50%) or a faint star that is coincident with the laser beacon (80%) as analyzed in Section 5. The total Strehl ratios are given by S = S_θS_ϕ. The probabilities for finding at least one sufficiently bright field star within the required angle to give a 50% tilt Strehil ratio are given for the galactic pole (P_pole) and for 30° galactic latitude (P_30°).