Adaptive Optics Imaging at 1–5 Microns on Large Telescopes:The COMIC Camera for ADONIS

Abstract

ABSTRACTA new 1–5 μm high‐resolution camera dedicated to the ESO adaptive optics system ADONIS has been developed as a collaborative project of Observatoire de Paris‐Meudon and Observatoire de Grenoble, under ESO contract. Since this camera has been designed to correctly sample the diffraction, two focal plate scales are available: 36 mas pixel−1 for the 1–2.5 μm range and 100 mas pixel−1 for the 3–5 μm range, yielding fields of view of 4.″5 × 4.″5 and 12.″8 × 12.″8, respectively. Several broadband and narrowband filters are available as well as two circular variable filters, allowing low spectral resolution (R ∼ 60–120) imagery between 1.2 and 4.8 μm. This camera is equipped with a 128 × 128 HgCdTe/CCD array detector built by the CEA‐LETI‐LIR (Grenoble, France). Among its main characteristics, this detector offers a remarkably high storage capacity (more than 106 electrons) with a total system readout noise of ≈1000 electrons rms, making it particularly well suited for long integration time imagery in the 3–5 μm range of the near‐infrared domain. The measured dark current is 2000 electrons s−1 pixel−1 at the regular operating temperature of 77 K, allowing long exposure times at short wavelengths (λ<3 μm), where the performances are readout‐noise limited. At longer wavelengths (λ>3 μm), the performances are background‐noise limited. We have estimated the ADONIS + COMIC imaging performances using a method specially dedicated to high angular resolution cameras.