Hamid Mehrgan

ESO infrared detector high-speed array control and processing electronic IRACE

The ESO IR detector high speed array control and processing electronic IRACE is designed as a modular system and supports readout and data processing of arrays with four as well as multiple output channels. In addition the system can handle multiple separate arrays and the data re routed to multiple processing chains. Detector front-ends are galvanically separated form data processing and system administration with fiberoptic links. Interfaces to different data processing systems for on-line data handling are implemented. The paper describes principles of system operation, and the achieved readout and on-line processing speeds.

Performance of large-format HgCdTe and InSb arrays for low-background applications

The first VLT IR instrument, ISAAC, was installed at the 8 meter Antu telescope in 1998. Experience and results with both InSb and HgCdTe large format arrays will be reported. Effects limiting the performance and strategies to partially overcome these limitations will be discussed.

Infrared detector development programs for the VLT instruments at the European Southern Observatory

Instrument platforms like the VLT represent a new challenge to IR focal plane technology. Since the large telescope diameter and the improved image quality provided by adaptive optics reduce the pixel scale, larger array formats are needed. To meet this challenge ESO is participating in development programs for both InSb and HgCdTe large format arrays. To cover the spectral region of 1 to 5 micron ESO has funded a foundry run at SBRC to produce 1024 X 1024 InSb arrays, which will be installed in ISAAC, the IR Spectrometer and Array Camera built for the VLT. Since the delivery of the 1K X 1K InSb array is delayed, the test results obtained with a 256 X 256 InSb array and the application of off chip cryogenic amplifiers to InSb detectors will be discussed. Results obtained with a (lambda) c equals 2.5 micrometers Rockwell 1024 X 1024 HgCdTe array will be presented, where an off chip cryogenic operational amplifier was used yielding a rms read noise of 3 electrons. Sensitivity profiles of individual pixels have been measured with a single mode IR fiber. Limitations of PACE 1 technology, such as persistence, will be discussed. First results with the 1K X 1K array, which was installed in SOFI, an IR focal reducer providing 1-2.5 micron imaging and long slit grism spectroscopy at the NTT telescope, will be presented. Advanced techniques of real time image sharpening will also be included. An outlook to the development of (lambda) c equals 2048 X 2048 HgCdTe array formats will be given. The optical layout of NIRMOS, a multi-object spectrograph for the VLT telescope, is base don the availability of 2K X 2K HgCdTe arrays.

Test Results with 2K×2K MCT Arrays

The performance of both an LPE 2K×2K engineering grade and a science grade array has been evaluated. Both arrays have a cut-off wavelength of λc=2.6 μm. At an operating temperature of 60 K, the dark current of the science grade array is 0.004 ē/sec. The peak quantum efficiency of the science grade array is 84.4%. The readout noise is 14 ē rms for a double correlated clamp and 5 ē rms for readout with 16 Fowler pairs.

CRIRES: a high-resolution infrared spectrograph for the VLT

CRIRES is a cryogenic, pre-dispersed, infrared echelle spectrograph designed to provide a resolving power of 105 between 1 and 5 μm at a Nasmyth focus of one of the 8m VLT telescopes. A curvature sensing adaptive optics sytem feed is used to minimize slit losses and a 4096x512 pixel mosaic of Aladdin arrays is being developed to maximixe the free spectral range covered in each order. Insertion of gas cells to measure high precision radial velocities is foreseen and the possibility of combining a Fresnel rhomb with a Wollaston prism for magnetic Doppler imaging is under study. Installation at the VLT is scheduled during the second half of 2004. Here we briefly recall the major design features of CRIRES and describe its current development status.

Megapixel infrared arrays at the European Southern Observatory

For the next generation of instruments which will be used at 8 m telescopes large format arrays are needed. Better image quality obtained by adaptive optics requires sampling to higher spatial frequencies. The large field of these instruments increases the demand for array formats as large as 1024 by 1024 and beyond. For this reason ESO is committed to the development of megapixel infrared detectors. In a multimode instrument covering the 1 to 5 micrometer spectral range a detector has to fulfill very different requirements. For high resolution spectroscopy low dark current and read noise are required. For broad band thermal imaging a high well capacity is needed to reduce the speed required to read out the array before it saturates. This paper gives a status report of ESOs activities related to large format arrays. An ultrafast data acquisition system has been developed to read out large format arrays. The performance goal is to achieve shot noise limited operation in the wavelength region of lambda equals 1 to 5 micrometer. The array controller is capable of handling the high data rates generated in the thermal infrared. The design of the controller was mainly driven by the requirement to read out the 32 parallel video channels of the SBRC 1024 by 1024 InSb detector in 50 msec. The array controller can also cope with the low read noise required for flux levels of less than 1 photon/sec. A new test camera for large format arrays has also been built. First test results obtained with the Rockwell 1024 by 1024 HgCdTe array are presented. The noise and dark current performance will be discussed with regard to OH line suppression. Read speed requirements will be defined for advanced readout techniques of image sharpening applying on chip tracking in the multiple nondestructive readout mode.

IR Detector Developments at Eso

New developments carried out for the next generation VLT instruments are discussed. Both HgCdTe and InSb large format arrays are used to cover the near infrared spectral region. A three-side buttable mosaic package for Aladdin InSb arrays will fill the focal plane of a high-resolution echelle spectrograph. Three instruments, a multi-object spectrograph, an integral field spectrograph and a test camera for multi-conjugate adaptive optics, will be equipped with HAWAII-II and HAWAII-II RG arrays. A fringe tracker of the VLT interferometer will use a PICNIC array which is optimized for use in an active control loop.

Design of the CRIRES 512×4096 Pixel Aladdin InSB Focal Plane Array Detector Mosaic

Near infrared focal plane technology has developed rapidly during the past decade. The array format has increased exponentially and surpassed the megapixel threshold. For the high-resolution IR Echelle Spectrometer CRIRES (1–5 μm range), to be installed at the VLT in 2004, ESO is developing a 512×4096 pixels focal plane array mosaic based on Raytheon Aladdin II and III InSB detectors with a cutoff wavelength of 5.2 μm. To fill the useful field of 135 mm in the dispersion direction and 21 mm in the spatial direction and to maximize simultaneous spectral coverage, a mosaic solution similar to CCD mosaics has been envisioned. It allows a minimum spacing between the detectors of 264 pixels. ESO developed a 3-side buttable multilayer co-fired AlN ceramic chip carrier and package for both the Aladdin II and Aladdin III detectors. This paper presents the design of the CRIRES 512×4096 pixels Aladdin InSb focal plane array mosaic and the newly developed 3-side buttable package.

Connection between detector front end and number cruncher with a 1-gigabit-per-second multiplexing fiber optic link

A fiberoptic link with a transmission rate of 1 gigabit/s is used in the ESO IR data acquisition system. The link connects the detector front-end with a multiprocessor system, based on T9000 transputers. The link not only transmits data -- the architecture of the system allows distribution of data to the multiprocessor system in a flexible and simple way. The paper describes principles of link operation, why this speed is required, and briefly the components used.