[Show abstract][Hide abstract] ABSTRACT: A Hubble space telescope wide field camera 3 e2v CCD was irradiated while operating at -84°C and the dark current studied as a function of temperature while the charge coupled device was warmed to a sequence of temperatures up to a maximum of +30°C. The device was then cooled back down to -84° and remeasured. Hot pixel populations were tracked during the warm up and cool down. Hot pixel annealing began below -40°C and the anneal process was largely completed by the time the detector reached +20°C. There was no apparent sharp annealing temperature. Although a large fraction of the hot pixels fell below the threshold to be counted as a hot pixel, they nevertheless sustained a higher leakage rate than the remaining population. The mechanism for hot pixel annealing is not presently understood. Room temperature irradiations do not adequately characterize the hot pixel distributions for cooled applications.
[Show abstract][Hide abstract] ABSTRACT: We present measurements of proton-induced single event transients in ultra-low noise HgCdTe IR detector arrays being developed for space-based astronomy and compare to modeling results.
[Show abstract][Hide abstract] ABSTRACT: The near-IR channel of Wide Field Camera 3, an instrument being developed for installation onto the Hubble Space Telescope, employs a Rockwell Scientific Company 1K x 1K HgCdTe detector array hybridized to a Hawaii-1R multiplexer. Radiation testing of test detectors showed that the WFC3 detectors do not exhibit a post-SAA glow of the sort seen in the NICMOS detectors. However, an anomalously high background was observed during the irradiation in the proton beam. This background goes away promptly when the beam is turned off. Subsequent testing and analysis revealed that the background arises due to emission of photons from within the CdZnTe detector substrate at the blue transmission edge of the substrate material. Further testing of devices with the substrate removed show no excess background signal. These results lead to a recommendation that the CdZnTe substrate material should be removed for space applications which require the ability to detect faint objects.
[Show abstract][Hide abstract] ABSTRACT: Two IR detectors have been selected as prime and spare flight parts for the IR channel of the Wide Field Camera 3 (WFC3). WFC3 is the panchromatic camera to be installed on the Hubble Space Telescope in Servicing Mission 4. The two devices, produced by Rockwell Scientific, are based on HgCdTe photoactive material MBE grown on ZnCdTE substrate with cutoff at 1.7mu m, and are hybridized on a 1Kx1K Hawaii-1R multiplexer. We present the detector performances, as result from the tests performed at the Detector Characterization Laboratory at the NASA-Goddard Space Flight Center. On the basis of the observed parameters, we estimate the sensitivity of the instrument in a number of representative filters and observing modes.
[Show abstract][Hide abstract] ABSTRACT: Wide Field Camera 3 (WFC3), which is to be installed on the Hubble Space Telescope during Servicing Mission 4, will employ a 1Kx1K Rockwell HgCdTe detector in the focal plane of its IR channel. In-depth studies of the performance of these detectors have been made at the GSFC Detector Characterization Lab. These detectors represent a significant improvement in performance over earlier generations of IR detectors. We present here the results of detailed investigations of the on-board reference pixels, noise properties, bias stability and other features of these devices. The scientific performance of the flight-selected detectors is presented in a companion paper by Robberto et.al.
[Show abstract][Hide abstract] ABSTRACT: Wide Field Camera 3 (WFC3) is an instrument being developed for installation on the Hubble Space Telescope in 2004. Two options are available for mitigating the degradation of the charge transfer efficiency (CTE) of the instrument's CCDs during the mission lifetime. The first is to use a pre-flash, similar to that adopted by the Advanced Camera for Surveys. The second is to make use of the charge injection capability of the E2V CCDs which have been selected for the WFC3. This capability permits the injection of charge in either discrete rows or in a "flat field" mode. We compare the utility of the pre-flash and charge injection techniques in restoring improved CTE and the effective noise introduced by each method. The results of this study will guide the selection of the technique to be used by the WFC3.
[Show abstract][Hide abstract] ABSTRACT: We examine proton-damaged charge-coupled devices (CCDs) and
compare the charge transfer efficiency (CTE) degradation using extended
pixel edge response, first pixel response, and <sup>55</sup>Fe X-ray
measurements. CTEs measured on Marconi and Fairchild imaging sensors
CCDs degrade similarly at all signal levels, though some of the
Fairchild CCDs had a supplementary buried channel
[Show abstract][Hide abstract] ABSTRACT: Wide Field Camera 3 (WFC3) is an instrument being developed for installation on the Hubble Space Telescope in 2003. The instrument will include blue optimized CCDs in a near-UV/visible channel and a Mercury-Cadmium-Telluride (MCT) array in a near-IR channel. Engineering grade prototype CCD detectors from Marconi Applied Technologies and MCT detectors from Rockwell Science Center have recently been obtained by the project. The MCT detectors employ a new multiplexer, based on the earlier Hawaii-1 and Hawaii-2 designs. We present results from the initial testing of these devices, emphasizing the performance parameters that are most important in defining the scientific capabilities of WFC3. All of the testing was performed at the Detector Characterization Laboratory at Goddard Space Flight Center.
[Show abstract][Hide abstract] ABSTRACT: Wide Field Camera 3 (WFC3) is an instrument being developed for installation aboard the Hubble Space Telescope in 2003. The camera will include both a near-UV/visible and a near-IR channel. The near-IR channel will use a HgCdTe detector custom designed by the Rockwell Science Center to have a long wavelength sensitivity cutoff at 1.7 microns. We present test results obtained with the pathfinder engineering grade detectors for this program. Of particular importance are the dark current and the position of the long wavelength cutoff, since these are two of the critical detector parameters which will determine the scientific capabilities of the instrument. All of the testing was performed at the Detector Characterization Laboratory (DCL) at Goddard Space Flight Center.
[Show abstract][Hide abstract] ABSTRACT: Rockwell Scientific Company is developing a new type of HgCdTe 1K×1K detector, called WFC3-1R, with cutoff wavelength at 1.7µm and 150K operating temperature. The detector will be installed on the Wide Field Camera 3, the fourth generation panchromatic instrument for the Hubble Space Telescope (HST) to be installed during HST Servicing Mission 4, currently scheduled for 2004. The detector uses HgCdTe MBE grown on a CdZnTe substrate and a new type of multiplexer, the Hawaii-1R MUX. Six lots of detectors have been produced so far, and have demonstrated the capability to meet or exceed the project requirements. In particular, detectors show quantum efficiency as high as ~90% at λ=1.4-1.6µm and greater than 50% at λ>1.0µm, readout noise of 30 e -rms with double correlated sampling, and dark current <0.2 e/s/pix at 150K. We illustrate the behavior of the reference pixels, showing that they allow the compensation of drifts in the dc output level. A number of detectors show a peculiar instability related to the variations of diode polarization, still under investigation. We also report on the environmental testing needed to qualify the WFC3-1R detectors as suitable for flight on the HST. We finally provide an update of the project status.