James W. Beletic

Teledyne Imaging Sensors: infrared imaging technologies for astronomy and civil space

Teledyne Imaging Sensors develops and produces high performance infrared sensors, electronics and packaging for astronomy and civil space. These IR sensors are hybrid CMOS arrays, with HgCdTe used for light detection and a silicon integrated circuit for signal readout. Teledyne manufactures IR sensors in a variety of sizes and formats. Currently, the most advanced sensors are based on the Hawaii-2RG (H2RG), 2K×2K array with 18 μm pixel pitch. The HgCdTe detector achieves very low dark current (<0.01 e-/pixel/sec) and high quantum efficiency (80-90%) over a wide bandpass. Substrate-removed HgCdTe can simultaneously detect visible and infrared light, enabling spectrographs to use a single focal plane array (FPA) for Visible-IR sensitivity. The SIDECARTM ASIC provides focal plane electronics on a chip, operating in cryogenic environments with very low power (<11 mW). The H2RG and SIDECARTM have been qualified to NASA Technology Readiness Level 6 (TRL-6). Teledyne continues to advance the state-of-the-art and is producing a high speed, low noise array designed for IR wavefront sensing. Teledyne is also developing a 4K×4K, 15 µm pixel infrared array that will be a cost effective module for the large focal planes of the Extremely Large Telescopes and future generation space astronomy missions.

Development of sensitive long-wave infrared detector arrays for passively cooled space missions

Abstract. The near-earth object camera (NEOCam) is a proposed infrared space mission designed to discover and characterize most of the potentially hazardous asteroids larger than 140 m in diameter that orbit near the Earth. NASA has funded technology development for NEOCam, including the development of long wavelength infrared detector arrays that will have excellent zodiacal background emission-limited performance at passively cooled focal plane temperatures. Teledyne Imaging Sensors has developed and delivered for test at the University of Rochester the first set of approximately 10 μm cutoff, 1024×1024 pixel HgCdTe detector arrays. Measurements of these arrays show the development to be extremely promising: noise, dark current, quantum efficiency, and well depth goals have been met by this technology at focal plane temperatures of 35 to 40 K, readily attainable with passive cooling. The next set of arrays to be developed will address changes suggested by the first set of deliverables.

Teledyne Imaging Sensors: silicon CMOS imaging technologies for x-ray, UV, visible, and near infrared

Teledyne Imaging Sensors develops and produces high performance silicon-based CMOS image sensors, with associated electronics and packaging for astronomy and civil space. Teledynes silicon detector sensors use two technologies: monolithic CMOS, and silicon PIN hybrid CMOS. Teledynes monolithic CMOS sensors are large (up to 59 million pixels), low noise (2.8 e- readout noise demonstrated, 1-2 e- noise in development), low dark current (<10 pA/cm2 at 295K) and can provide in-pixel snapshot shuttering with >103 extinction and microsecond time resolution. The QE limitation of frontside-illuminated CMOS is being addressed with specialized microlenses and backside illumination. A monolithic CMOS imager is under development for laser guide star wavefront sensing. Teledynes hybrid silicon PIN CMOS sensors, called HyViSITM, provide high QE for the x-ray through near IR spectral range and large arrays (2K×2K, 4K×4K) are being produced with >99.9% operability. HyViSI dark current is 5-10 nA/cm2 (298K), and further reduction is expected from ongoing development. HyViSI presently achieves <10 e- readout noise, and new high speed HyViSI arrays being produced in 2008 should achieve <4 e- readout noise at 900 Hz frame rate. A Teledyne 640×480 pixel HyViSI array is operating in the Mars Reconnaissance Orbiter, a 1K×1K HyViSI array will be launched in 2008 in the Orbiting Carbon Observatory, and HyViSI arrays are under test at several astronomical observatories. The advantages of CMOS in comparison to CCD include programmable readout modes, faster readout, lower power, radiation hardness, and the ability to put specialized processing within each pixel. We present one example of in-pixel processing: event driven readout that is optimal for lightning detection and x-ray imaging.

Commentary: JWST near-infrared detector degradation— finding the problem, fixing the problem, and moving forward

The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared-optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST’s four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 μm cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a “Detector Degradation Failure Review Board” (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article, we present the two public DD-FRB “Executive Summaries” that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight. We supplement these with a brief introduction to H2RG detector arrays, some recent measurements showing that the performance of the improved design meets JWST requirements, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs.

H2RG focal plane array and camera performance update

Teledyne’s H2RG focal plane arrays have been widely used in scientific infrared and visible instruments for ground-based and space-based telescopes. The majority of applications use the H2RG with 2.5 micron cutoff HgCdTe detector pixel at an operating temperature of ~77 K (LN2). The exceptionally low dark current of the 2.5 micron H2RG allows for operation at higher temperatures which facilitates simplified instrument designs and therefore lower instrument cost. Performance data of 2.5 micron H2RG arrays at 77K, 100 K, and 120 K are presented and are discussed as a function of detector bias and pixel readout rate. This paper also presents performance data of 1.75 micron and 5.3 micron H2RG focal plane arrays and discusses some of the inherent performance differences compared to 2.5 micron cutoff arrays. A complete infrared camera system that uses the H2RG focal plane array and SIDECAR ASIC focal plane electronics is introduced.

VIMOS and NIRMOS multi-object spectrographs for the ESO VLT

The VIRMOS consortium of French and Italian Institutes is manufacturing 2 wide field imaging multi-object spectrographs for the European Southern Observatory Very Large Telescope, with emphasis on the ability to carry over spectroscopic surveys of large numbers of sources. The Visible Multi-Object Spectrograph, VIMOS, is covering the 0.37 to 1 micron wavelength domain, with a full field of view of 4 by 7 by 8 arcmin2 in imaging and MOS mode. The Near IR Multi-Object Spectrograph, NIRMOS, is covering the 0.9 to 1.8 microns wavelength range, with afield of view 4 by 6 by 8 arcmin2 in MOS mode. The spectral resolution for both instrument scan reach up to R equals 5000 for a 0.5 arcsec wide slit. Multi-slit masks are produced by a dedicated Mask Manufacturing Machine cutting through thin Invar sheets and capable of producing 4 slit masks approximately 300 by 300 mm each with approximately slits 5.7 mm long in less than one hour. Integral field spectroscopy is made possible in VIMOS by switching in the beam specially build masks fed by 6400 fibers coming form a 54 by 54 arcsec2 integral field head with a 80 by 80 array of silica micro-lenses. NIRMOS has a similar IFS unit with a field of 30 by 30 arcmin2. These instruments are designed to offer very large multiplexing capabilities. In MOS mode, about 1000 objects can be observed simultaneously with VIMOS, with a S/N equals 10 obtained on galaxies with I equals 24 in one hour, and approximately 200 objects can be observed simultaneously with NIRMOS, with a S/N equals 10 obtained don galaxies with J equals 22, H equals 20.6 in 1h at Req equals 200. We present here the status of VIMOS, currently under final integration, with expected first light in the summer 2000, together with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more with the final design of NIRMOS presented at the Final Design Review. The VLT-VIRMOS deep redshift survey of more than 150000 galaxies over the redshift range 0 < z < 5 will be undertaken based on 120 guaranteed nights awarded to the project.

Commissioning of a 4Kx4K CCD mosaic and the new ESO FIERA CCD controller at the SUSI-2 imager of the NTT

We present the characteristics of the new CCD imager, SUSI2, installed at the ESO 3.5 m NTT. The instrument shares the Nasmyth focus A with the new infrared imager-spectrograph SOFI. The focal plane array of USSI2 is a mosaic of 2 EEV44- 82, 2k X 4k, 15 micrometer pixels, thinned, anti-reflection coated CCDs, which are placed at the direct focus of the telescope (scale 0.08 arcsec/pixel, field of view 5.5 X 5.5 arcmin). The average QE for the two devices is 76, 90, 85, 80, 68, 49, 23% at 350, 400, 500, 600, 700, 800, 900 nm respectively. The overall instrument efficiency, including the three mirrors of the telescope and the detector but without filters, is computed to be 46, 55, 51, and 48% at the central wavelengths of the U, B, V and R bands. The CCDs are driven by the new ESO CCD controller FIERA. The system performance was measured during the commissioning of the instrument at the telescope in February 98. The mosaic is read in 16 seconds in the standard operating mode (2 X 2 binning of the CCDs) with a read-out-noise of 4.7 e-/pixel. The other CCD parameters such as CTE, dark current and linearity, were also found to comply with the requirements. The FWHM of stellar sources in images obtained in good seeing conditions were measured to be 0.49 arcsec, with no significant variation over the field of view.

A novel CCD design for curvature wavefront sensing

At the European Southern Observatory (ESO) in Garching, Germany, several adaptive optics systems using curvature wavefront sensors are being developed for the Very Large Telescope (VLT) and the VLT interferometer (VLTI). Curvature AO-systems have traditionally used avalanche photodiodes (APDs) as detectors due to strict requirements of very short integration times (200 microsec) and very low readout noise. Advances in CCD technology motivated an investigation of the use of a specially designed CCD as the wavefront sensor detector in a 60-element curvature AO system. A CCD has never been used before as the wavefront sensor in a low light level curvature adaptive optics system. This CCD can achieve nearly the same performance as APDs at a fraction of the cost and with reduced complexity for high order wavefront correction. Moreover the CCD has higher quantum efficiency and a greater dynamic range than APDs. A readout noise of less than 1.5 electrons at 4000 frames per second was achieved. Back-illuminated thinned versions of this CCD can replace APDs as a new detector for high order curvature wavefront sensing.

Follow the yellow-orange rabbit: a CCD optimized for wavefront sensing a pulsed sodium laser guide star

Most large telescopes are now implementing sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these systems plan to use the Shack-Hartmann approach for wavefront sensing. In these systems, the laser spots that are imaged in the Shack-Hartmann subapertures suffer spot elongation due to the 10 km extent of the sodium layer. The spot elongation extends radially from the projection point, and increases linearly with the distance the subaperture is separated from the laser. For 8-meter class telescopes with laser projection behind the secondary mirror, the spot elongation is ~1 arc sec at the edge of the pupil, and does not significantly affect the performance of the AO system. However, for the coming generation of extremely large telescopes, sodium LGS spot elongation will significantly degrade the quality of wavefront measurement. Attention should now be given to the development of technologies that can reduce or eliminate the spot elongation problem. The laser spot elongation can be greatly reduced by projecting the sodium laser in a series of short (1-3 μsec) pulses. The Lawrence Livermore National Laboratory (LLNL) has been funded to develop a pulsed fiber laser. In parallel, a new kind of wavefront sensor detector must be developed to properly sense the pulsed laser return. In this paper, we present our project that will develop a novel CCD which is optimized for sensing the return from a pulsed sodium LGS. Our CCD design uses custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This pixel geometry will allow each subaperture to follow the yellow-orange rabbit (i.e. the 589 nm laser pulse) as it traverses the sodium layer, providing optimal sampling of a limited number of detected photons. This CCD will attain photon-noise limited performance at high frame rates, using MOSFET amplifiers that exist today (2-3 electrons noise). However, we seek even lower noise amplifiers, and as part of our project, we are testing a new generation of JFET amplifiers that may attain sub-electron noise performance. The test CCD will be a standard geometry, 160x160 pixel image area with split frame transfer and a total of 20 readout ports. This test CCD will easily surpass the performance of the CCDs presently in use in astronomical AO systems, and should provide a significant performance improvement in the AO systems of the 8-10 meter telescopes. This project is a collaboration between the Keck Observatory, MIT Lincoln Laboratory, SciMeasure Analytical Systems, Gemini Observatory, Lick Observatory, the University of California, and the Rockwell Scientific Company. Our efforts are being coordinated with the developments at LLNL so that the pulsed laser and novel geometry CCD can be mated together in 3 years when both are fully developed.

A CCD-based Curvature Wavefront Sensor for Adaptive Optics in Astronomy

Advances in Charge-Coupled Device (CCD) technology motivated an investigation of the use of a specially designed CCD as the wavefront sensor detector in a 60 element curvature AO system. A CCD has never been used before as the wavefront sensor in a low light level curvature adaptive optics system. A CCD can achieve nearly the same performance as APDs at a fraction of the cost and with reduced complexity for high order wavefront correction. Moreover the CCD has higher quantum efficiency and a greater dynamic range an APD. A readout noise of less than 1.5 ē at 4000 frames/sec was achieved. A back-illuminated thinned version of this CCD can replace APDs as the best detector for high order curvature wavefront sensing.