The Ultraviolet Transient Astronomical Satellite (ULTRASAT) is a scientific UV space telescope that will operate in geostationary orbit. The mission, targeted to launch in 2024, is led by the Weizmann Institute of Science (WIS) in Israel and the Israel Space Agency (ISA). Deutsches Elektronen Synchrotron (DESY) in Germany is tasked with the development of the UV-sensitive camera at the heart of the telescope. The camera's total sensitive area of ≈90mm x 90mm is built up by four back-side illuminated CMOS sensors, which image a field of view of ≈200 deg2. Each sensor has 22:4 megapixels. The Schmidt design of the telescope locates the detector inside the optical path, limiting the overall size of the assembly. As a result, the readout electronics is located in a remote unit outside the telescope. The short focal length of the telescope requires an accurate positioning of the sensors within ±50 μm along the optical axis, with a flatness of ±10 μm. While the telescope will be at around 295K during operations, the sensors are required to be cooled to 200K for dark current reduction. At the same time, the ability to heat the sensors to 343K is required for decontamination. In this paper, we present the preliminary design of the UV sensitive ULTRASAT camera.
We report on ongoing scientific CCD detector and control electronic developments at STA. Recent astrometric and spectroscopic instruments are pushing for highly uniform pixel arrays. We present results from sensors fabricated with high resolution 1X masks aimed at minimizing the random and periodic pixel nonuniformities introduced during manufacture. Instrument requirements for large next generation telescopes tend to target larger arrays with larger pixels. We introduce the STA4500, a four output 6120 x 6120 15um CCD intended for these applications. The device includes dual transfer gates before the serial register to allow slow, high CTE vertical transfers to occur simultaneous with serial readout. We also present our next experimental high dynamic range CCD. This sensor uses dual outputs operating in parallel with different sensitivities to greatly expand the linear dynamic range achievable with large pixel scientific sensors without impairing noise or readout rate. Finally, we describe updates to our Archon astronomical CCD controller. Improvements include daisy chained multi-controller synchronization for mosaic readout, high resolution thermal control for sub-milliKelvin temperature stability, and high voltage biases up to +/-100V for operating deep depletion CCDs.
The demand from the astronomical community for high resolution low noise CCDs has led to the development of the
STA1600LN, a 10560 × 10560 pixel, 95mm × 95mm, full-frame CCD imager with 9×9 μ2 pixels. The device
improvements include noise reduction to below 3ē at 100kHz, improved quantum efficiency, as well as packaging
developments for improved fill factor in mosaic systems. We provide test results from production devices, along with
updates on scientific systems utilizing the STA1600 for astronomy.
The Geostationary Lightning Mapper (GLM) instrument selected to fly on the National Oceanic and Atmospheric
Administration (NOAA) GOES-R Series environmental satellites has very unique requirements as compared to an
imaging array. GLM's requirements to monitor lightning on a continental scale will provide new insight into the
formation, distribution, morphology and evolution of storms.
A 500 frame per second backside illuminated frame transfer CCD imager (STA3900A) with variable pixel size has
been developed to meet these requirements. A variable pixel architecture provides a near uniform mapping of the curved
surface of the earth, while 56 outputs running at 20 MHz yield greater than a 1.1 Gigapixel per second data rate with low
RMS noise and high MTF. This paper will provide detailed information on design trades required. We will report CCD
read noise, dark current, full well capacity, and quantum efficiency (QE).
A 10k x 10k single-chip CCD camera was installed on the first Antarctic Survey Telescope (AST3-1) at Dome A,
Antarctica in January 2012. The pixel size is 9 μm, corresponding to 1 arcsec on the focal plane. The CCD runs
without shutter but in frame transfer mode, and is cooled by thermoelectric cooler (TEC) to take advantage
of the low air temperature at Dome A. We tested the performance of the camera in detail, including the gain,
linearity, readout noise, dark current, charge transfer efficiency, etc. As this camera is designed to work at Dome
A, where the lowest air temperature could go down to −80°C in winter, we tested to cool not only the CCD
chip but also the controller which usually is operated at normal temperatures for ground-based telescopes. We
found that the performance of the camera changes a little when the controller is cooled.
The WIYN One Degree Imager (ODI) will provide a one degree field of view for the WIYN 3.5 m telescope located on
Kitt Peak near Tucson, Arizona. Its focal plane consists of an 8x8 grid of Orthogonal Transfer Array (OTA) CCD
detectors. These detectors are the STA2200 OTA CCDs designed and fabricated by Semiconductor Technology
Associates, Inc. and backside processed at the University of Arizona Imaging Technology Laboratory. Several lot runs
of the STA2200 detectors have been fabricated. We have backside processed devices from these different lots and
provide detector performance characterization, including noise, CTE, cosmetics, quantum efficiency, and some
orthogonal transfer characteristics. We discuss the performance differences for the devices with different silicon
thickness and resistivity. A fully buttable custom detector package has been developed for this project which allows
hybridization of the silicon detectors directly onto an aluminum nitride substrate with an embedded pin grid array. This
package is mounted on a silicon-aluminum alloy which provides a flat imaging surface of less than 20 microns peakvalley
at the -100 C operating temperature. Characterization of the package performance, including low temperature
profilometry, is described in this paper.
A 52-M pixel, 71mm x 54mm, full-frame CCD imager with 8.6 um x 8.6 um pixel size has been
developed for use in high speed scanning applications. On-going interest for ultra-high resolution, high
speed imagers for electronic imaging OEM customers in various scientific markets including spectroscopy
and digital photography has led to the development of the STA2500A. Innovative design techniques were
utilized in the production of this device. 32 outputs running at 40 Mhz yield a 20Hz frame rate with low
RMS noise and high MTF. This paper will provide detailed information on design trades developed for
high-speed imagers leading to the design and performance capabilities of the STA2500A, as well as a
description of the electronics required for its use.
The WIYN One Degree Imager (ODI) will provide a one degree field of view for the WIYN 3.5 m telescope located on Kitt Peak near Tucson, Arizona. Its focal plane will consist of an 8x8 grid of Orthogonal Transfer Array (OTA) CCD detectors with nearly one billion pixels. The implementation of these detectors into the focal plane has required the development of several novel packaging and characterization techniques, which are the subject of this paper. We describe a new packaging/hybridization method in which the CCD die are directly bonded to aluminum nitride ceramic substrates which have indium bump on one side and brazed pins on the other. These custom packages allow good thermal conductivity, a flat imaging surface, four side buttability, and in situ testing of the devices during backside processing. We describe these carriers and the backside processing techniques used with them. We have also modified our cold probing system to screen these OTA die at wafer level to select the best candidates for backside processing. We describe these modifications and characterization results from several wafer lots.
A full-wafer, 10,580 × 10,560 pixel (95 × 95 mm) CCD was designed and tested at Semiconductor Technology
Associates (STA) with 9 μm square pixels and 16 outputs. The chip was successfully fabricated in 2006 at DALSA
and some performance results are presented here. This program was funded by the Office of Naval Research
through a Small Business Innovation in Research (SBIR) program requested by the U.S. Naval Observatory for
its next generation astrometric sky survey programs. Using Leach electronics, low read-noise output of the 111
million pixels requires 16 seconds at 0.9 MHz. Alternative electronics developed at STA allow readout at 20
MHz. Some modifications of the design to include anti-blooming features, a larger number of outputs, and use
of p-channel material for space applications are discussed.
A 111-Mega pixel, 92x92 mm2, full-frame CCD imager with 9x9 um2 pixel size has been developed for use in scientific
applications. Recent interest for ultra-high resolution imagers for electronic imaging OEM customers in various
scientific markets, including biotechnology, microscopy, crystallography, astronomy, spectroscopy, and aerial
reconnaissance markets has lead to the development of the STA1600A 111-Mega pixel monochromatic charge-coupled
device. Innovative design techniques were utilized in the early development of this device, yielding low RMS noise and
high MTF for readout speeds ranging from 1 Mpixel/s to 25 Mpixel/sec. This paper will provide detailed information on
the design and performance capabilities of the STA1600A, as well as background information on the commercial uses of
this device.
Due to aggressive scientific specifications, Semiconductor Technology Associates and
the University of Arizona's Imaging Technology Laboratory have collaborated to
develop a fully depleted back illuminated CCD for scientific imaging. These devices are
designed to target increased quantum efficiency into the near-infrared, without reduction
in the modulation transfer function, charge transfer efficiency, or rms noise. The
STA1700 series imagers are back illuminated 100 micron thick devices with a 10 micron
pixel pitch targeted to meet the requirements of the Large Synoptic Survey Telescope
(LSST). Recent characterization results will be presented including the point spread
function of a 2 micron spot. Also discussed will be the thinning and packaging
developments for the STA1700. These efforts include the addition of a backside bias
contact, invar package design with high density connectors, as well as etching and
backside coating optimization for high resistivity silicon.
A 111-Mega pixel, 92×92 mm2, full-frame CCD imager with 9×9 um2 pixel size has been developed for use in scientific
applications. Recent interest for ultra-high resolution imagers for electronic imaging OEM customers in various
scientific markets, including biotechnology, microscopy, crystallography, astronomy, spectroscopy, and digital
photography markets has lead to the development of the STA1600A 111-Mega pixel monochromatic charge-coupled
device. Innovative design techniques were utilized in the early development of this device, yielding low RMS noise and
high MTF for readout speeds ranging from 1 Mpixel/s to 10 Mpixel/sec. This paper will provide detailed information on
the design and performance capabilities of the STA1600A, as well as background information on the commercial uses of
this device.
A 111-Mega pixel, 92x92 mm2, full-frame CCD imager with 9x9 um2 pixel size has been developed for use in scientific
applications. Recent interest for ultra-high resolution imagers for electronic imaging OEM customers in various
scientific markets, including biotechnology, microscopy, crystallography, astronomy, spectroscopy, and digital
photography markets has lead to the development of the STA1600A 111-Mega pixel monochromatic charge-coupled
device. Innovative design techniques were utilized in the early development of this device, yielding low RMS noise and
high MTF for readout speeds ranging from 1 Mpixel/s to 10 Mpixel/sec. This paper will provide detailed information on
the design and performance capabilities of the STA1600A, as well as background information on the commercial uses of
this device.
Recent discoveries show new promise for a formerly assumed extinct technology, CCDs. A primary limitation to the implementation of new ground-based astronomy measurement techniques is the inaccuracy of navigation and targeting due to error in the celestial frame of reference. This celestial frame of reference is relied upon for satellite attitude determination, payload calibration, in-course missile adjustments, space surveillance, and accurate star positions used as fiducial points. STA will describe the development of an ultrahigh resolution CCD (up to the maximum limit of a 150 mm wafer) that integrates high dynamic range and fast readout that will substantially decrease the error in the celestial reference frame. STA will also discuss prior and ongoing experience with large area CCD focal-plane arrays which include innovative design and fabrication techniques that ensure performance and yield.
Past and present revelations within scientific imaging have stressed the importance of CCD small signal sensitivity. Current characterization techniques use a Fe55 soft x-ray source to determine charge transfer and noise, however rendering signal sensitivity less than 1620 e- unknown. CCD evolution has brought forth innovative design and fabrication techniques to decrease device noise and increase device sensitivity, enabling low level imaging. This paper presents a simple approach to characterizing the transfer functions, linearity, noise, and output sensitivity at low signal levels, thus confirming the true capabilities of the imager. This characterization technique also validates the quality of the base material and process via low level trap testing. The characterization method uses fluoresce x-rays from target materials to illuminate the imager.
The orthogonal-transfer array (OTA) is a new CCD architecture designed to provide wide-field tip-tilt correction of astronomical images. The device consists of an 8x8 array of small (~500x500 pixels) orthogonal-transfer CCDs (OTCCD) with independent addressing and readout of each OTCCD. This approach enables an optimum tip-tilt correction to be applied independently to each OTCCD across the focal plane. The first design of this device has been carried out at MIT Lincoln Laboratory in support of the Pan-STARRS program with a collaborative parallel effort at Semiconductor Technology Associates (STA) for the WIYN Observatory. The two versions of this device are functionally compatible and share a common pinout and package. The first wafer lots are complete at Lincoln and at Dalsa and are undergoing wafer probing.
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