Optical Charge-coupled Device Research Articles

Energy Saving Thermal Management of Space Remote Sensor and Validation

An energy-efficient thermal control management method for space remote sensors using optical, mechanical, electrical, and thermal integration is proposed. The satellite power resources are insufficient, so an energy-efficient loop heat pipe (LHP) is designed for six intermittently operating detectors. The charge-coupled device (CCD) has a total heat generation of 72 W and operates for 8 min per orbital cycle. The LHP includes a capillary pump, six cold plates, and two radiators. The working fluid of the LHP is high-purity ammonia and the material of the wick is ceramic. The drive power on the capillary pump evaporator automatically switches between 30 W and 90 W depending on the operating mode of the remote sensor, resulting in an average power saving of about 58.2% compared to a conventional LHP. For the optical structure, a three-stage insulation technology was developed to save heater power and improve temperature stability. A transient numerical simulation model of the LHP was developed to study the vapor–liquid zone of two radiators under the condition of rapid power change. Vacuum thermal tests were conducted and the test data agreed well with the numerical simulation results. The in-orbit temperature data showed that the temperature fluctuations of the optical structure and CCD were less than ±0.2 °C and ±0.8 °C, respectively.

A low-cost liquid refractive index sensor based on plastic optical fibre and CCD array

A wireless refractive index sensor for in-line measurement in liquids was developed. It is based on the Fresnel reflection on a prism–liquid interface, where the critical angle of the totally reflected light in the interface of two media is detected by a charge-coupled device (CCD) array. A LED is used as a light source and a plastic optical fibre, with a well-established numeric aperture, guides the light to the prism interface. Both the LED and the CCD are controlled with a Raspberry Pi 3 Model B board with wireless communication. Resolutions with values lower than 1.0 × 10−4 RIU can be achieved with this potential low-cost configuration.

An optical test bench for the precision characterization of absolute quantum efficiency for the TESS CCD detectors

The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright stars with Ic ≲ 13. TESS has been selected by NASA for launch in 2018 as an Astrophysics Explorer mission, and is expected to discover a thousand or more planets that are smaller in size than Neptune. TESS will employ four wide-field optical charge-coupled device (CCD) cameras with a band-pass of 650 nm–1050 nm to detect temporary drops in brightness of stars due to planetary transits. The 1050 nm limit is set by the quantum efficiency (QE) of the CCDs. The detector assembly consists of four back-illuminated MIT Lincoln Laboratory CCID-80 devices. Each CCID-80 device consists of 2048×2048 imaging array and 2048×2048 frame store regions. Very precise on-ground calibration and characterization of CCD detectors will significantly assist in the analysis of the science data obtained in space. The characterization of the absolute QE of the CCD detectors is a crucial part of the characterization process because QE affects the performance of the CCD significantly over the redder wavelengths at which TESS will be operating. An optical test bench with significantly high photometric stability has been developed to perform precise QE measurements. The design of the test setup along with key hardware, methodology, and results from the test campaign are presented.

A Practical Deconvolution Computation Algorithm to Extract 1D Spectra from 2D Images of Optical Fiber Spectroscopy

Bolton & Schlegel presented a promising deconvolution method to extract one-dimensional (1D) spectra from a two-dimensional (2D) optical fiber spectral CCD (charge-coupled device) image. The method could eliminate the PSF (point-spread function) difference between fibers, extract spectra to the photo noise level, as well as improve the resolution. But the method is limited by its huge computation requirement and thus can not be implemented in actual data reduction. In this article, we develop a practical computation method to solve the computation problem. The new computation method can deconvolve a 2D fiber spectral image of any size with actual PSFs, which may vary with positions. Our method does not require large amounts of memory and can extract a 4 k × 4 k noise-free CCD image with 250 fibers in 2 hr. To make our method more practical, we further consider the influence of noise, which is thought to be an intrinsic ill-posed problem in deconvolution algorithms. We modify our method with a Tikhonov regularization item to depress the method induced noise. We do a series of simulations to test how our method performs under more real situations with Poisson noise and extreme cross talk. Compared with the results of traditional extraction methods, i.e., the Aperture Extraction Method and the Profile Fitting Method, our method has the least residual and influence by cross talk. For the noise-added image, the computation speed does not depend very much on fiber distance, the signal-to-noise ratio converges in 2–4 iterations, and the computation times are about 3.5 hr for the extreme fiber distance and about 2 hr for nonextreme cases. A better balance between the computation time and result precision could be achieved by setting the precision threshold similar to the noise level. Finally, we apply our method to real LAMOST (Large sky Area Multi-Object fiber Spectroscopic Telescope; a.k.a. Guo Shou Jing Telescope) data. We find that the 1D spectrum extracted by our method has both higher signal-to-noise ratio and resolution than the traditional methods, but there are still some suspicious weak features, possibly caused by the method around the strong emission lines. As we have demonstrated, our deconvolution method has solved the computation problem and progressed in dealing with the noise influence. Multifiber spectra extracted by our method will have higher resolution and signal-to-noise ratio, and thus will provide more accurate information (such as higher radial velocity and metallicity measurement accuracy in stellar physics) to astronomers than traditional methods.

Objective Beach-State Classification From Optical Sensing of Cross-Shore Dissipation Profiles

Remote sensing using terrestrial optical charge-coupled device cameras is a useful data collection method for geophysical measurement in the nearshore zone, where in situ measurement is difficult and time consuming. In particular, optical video sensing of the variability in human-visible surface refraction due to the nearshore incident wave field is becoming an established method for distal measurement of nearshore subtidal morphology. We report on the use of a low-mounted shore-normal camera for gathering data on cross-shore dissipative characteristics of a dynamic open beach. Data are analyzed for the purposes of classifying three of Wright and Shorts' intermediate classes of morphological beach state as determined by expert raters. Although these beach states are usually thought of as being distinctive in terms of their longshore bar variability, theory predicts that differences should also be observed in cross-shore dissipative characteristics. Three methods of generating features from statistical features from the archived optical data are described and compared in terms of their ability to discriminate between the beach states. Principal component scores of the percentile distributions were found to provide slightly better classification performance (i.e., 85%, while approximating the data using relatively fewer features), whereas classification using intensity distributions alone resulted in the worst performance, classifying 78% of beach states correctly. Class center moment profiles for each beach state were constructed, and results indicate that cross-shore wave dissipation becomes more disorganized as linear bars devolve into more complex transverse structures

Firefly Luciferase Enzyme Fragment Complementation for Imaging in Cells and Living Animals

We identified different fragments of the firefly luciferase gene based on the crystal structure of firefly luciferase. These split reporter genes which encode for protein fragments, unlike the fragments currently used for studying protein-protein interactions, can self-complement and provide luciferase enzyme activity in different cell lines in culture and in living mice. The comparison of the fragment complementation associated recovery of firefly luciferase enzyme activity with intact firefly luciferase was estimated for different fragment combinations and ranged from 0.01 to 4% of the full firefly luciferase activity. Using a cooled optical charge-coupled device camera, the analysis of firefly luciferase fragment complementation in transiently transfected subcutaneous 293T cell implants in living mice showed significant detectable enzyme activity upon injecting d-luciferin, especially from the combinations of fragments identified (Nfluc and Cfluc are the N and C fragments of the firefly luciferase gene, respectively): Nfluc (1-475)/Cfluc (245-550), Nfluc (1-475)/Cfluc (265-550), and Nfluc (1-475)/Cfluc (300-550). The Cfluc (265-550) fragment, upon expression with the nuclear localization signal (NLS) peptide of SV40, shows reduced enzyme activity when the cells are cotransfected with the Nfluc (1-475) fragment expressed without NLS. We also proved in this study that the complementing fragments could be efficiently used for screening macromolecule delivery vehicles by delivering TAT-Cfluc (265-550) to cells stably expressing Nfluc (1-475) and recovering signal. These complementing fragments should be useful for many reporter-based assays including intracellular localization of proteins, studying cellular macromolecule delivery vehicles, studying cell-cell fusions, and also developing intracellular phosphorylation sensors based on fragment complementation.

Noninvasive imaging of lentiviral-mediated reporter gene expression in living mice

Lentiviral-mediated gene delivery holds significant promise for sustained gene expression within living systems. Vesicular stomatitis virus glycoprotein-pseudotyped human immunodeficiency virus type 1-based lentiviral vectors can be used to introduce transgenes in a broad spectrum of dividing as well as nondividing cells. In the current study, we construct a lentiviral vector carrying two reporter genes separated by an internal ribosomal entry site and utilize that virus in delivering both genes into neuroblastoma cells in cell culture and into cells implanted in living mice. We utilize two reporter genes, a mutant herpes simplex virus type 1 (HSV1) sr39tk as a reporter gene compatible with positron emission tomography (PET) and a bioluminescent optical reporter gene, firefly luciferase (Fluc), to image expression in living mice by an optical charge-coupled device (CCD) camera. By using this lentivirus, neuroblastoma (N2a) cells are stably transfected and a high correlation (R2 = 0.91) between expressions of the two reporter genes in cell culture is established. Imaging of both reporter genes using microPET and optical CCD camera in living mice is feasible, with the optical approach being more sensitive, and a high correlation (R2 = 0.86) between gene expressions is again observed in lentiviral-infected N2a tumor xenografts. Indirect imaging of HSV1-sr39tk suicide gene therapy utilizing Fluc is also feasible and can be detected with increased sensitivity by using the optical CCD. These preliminary results validate the use of lentiviral vectors carrying reporter genes for multimodality imaging of gene expression and should have many applications, including imaging of xenografts, metastasis, and cell trafficking as well as noninvasive monitoring of lentiviral-mediated gene delivery and expression.

Measurement of mass attenuation coefficients in air by application of detector linearity tests

Accurate knowledge of x-ray mass attenuation coefficients is essential for studies as diverse as atomic physics, materials science, and radiation safety. However, a significant discrepancy exists between theoretical tabulated results for air at soft x-ray energies. We outline a precision measurement of the mass attenuation coefficients for air at various energies using two types of detectors and a simple test of detector response. We discuss whether sufficient accuracy can be obtained using this data to distinguish between competing theoretical estimates. In the process, we investigate the intensity response of two common synchrotron x-ray detectors: an x ray to optical charge-coupled device camera using a crystal scintillator and an x-ray sensitive photodiode.

A Parkes half-Jansky sample of GHz peaked spectrum galaxies

This paper describes the selection of a new southern/equatorial sample of gigahertz peaked spectrum (GPS) radio galaxies, and subsequent optical charge-coupled device imaging and spectroscopic observations using the ESO 3.6-m telescope. The sample consists of 49 sources with −40 ◦ 20 ◦ and S2.7 GHz >0.5 Jy, selected from the Parkes PKSCAT90 survey. Approximately 80 per cent of the sources are optically identified, and approximately half of the identifications have available redshifts. The R-band Hubble diagram and evolution of the host galaxies of GPS sources are reviewed.

Optimizing data recording for the NIF core diagnostic x-ray streak camera

Quantitative measurements of the sensitivity, dynamic range, and image resolution of a Nova secondary ion mass-based x-ray streak camera have been made. Comparisons were made using film versus a 4k×4k optical charge-coupled device for data readout. These tests were performed with and without an optical image intensifier tube, and with a direct electron-sensitive microchannel plate. We present results from these tests and recommendations for the National Ignition Facility core x-ray streak camera.

Zw 1718.1-0108: a highly disturbed galaxy cluster at low Galactic latitude

We report the discovery of highly distorted X-ray emission associated with the nearby cluster Zw 1718.1–0108, one of the dominant members of which is the powerful radio galaxy 3C353. This cluster has been missed by previous X-ray cluster surveys because of its low Galactic latitude (b = 19.5°), despite its brightness in the hard X-ray band (2–10 keV flux of 1.2×10–11 erg cm−2 s−1). Our optical charge-coupled device image of the central part of the cluster reveals many member galaxies which are dimmed substantially by heavy Galactic extinction. We have measured redshifts of three bright galaxies near the X-ray emission peak and they are all found to be around z = 0.028. The ASCA gas imaging spectrometer and ROSAT high-resolution imager images show three aligned X-ray clumps embedded in low surface-brightness X-ray emission extended by ∼30 arcmin. The averaged temperature measured with ASCA is kT = 4.3±0.2 keV, which appears to be hot for the bolometric luminosity when compared with the temperature—luminosity correlation of galaxy clusters. The irregular X-ray morphology and evidence for a non-uniform temperature distribution suggest that the system is undergoing a merger of substructures. Since the sizes and luminosities of the individual clumps are consistent with those of galaxy groups, Zw 1718.1–0108 is interpreted as an on-going merger of galaxy groups in a dark matter halo forming a cluster of galaxies and thus is in a transition phase of cluster formation.

X-ray polarimetry and position measurement using the photoeffect and charge diffusion in a CCD

A new method of X-ray polarimetry based on the photoeffect in a highly segmented silicon charge coupled device (CCD) has been established using monochromatic synchrotron radiation and planar channeling radiation. For the smallest pixel dimensions (6.8 × 6.8 μm 2) available today in commercial optical CCD cameras an analyzing power for linear polarization in the order of 10% has been measured at energies above 10 keV. A strong energy dependence is observed in the energy range from 15 to 40 keV. In addition to events due to the photoeffect in the thin depleted front layer of the CCD, also diffusion spread events resulting from far more abundant conversions deeper inside the chip were found to be very useful for simultaneous measurements of polarization, energy and position with sub-pixel, submicron impact accuracy (0.9 μm rms at 15 keV). The spatial accuracy is in accord with expectations from Monte-Carlo simulations.

Astrometry for the Galileo mission. 1: Asteroid encounters

view Abstract Citations (8) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Astrometry for the Galileo Mission. I. Asteroid Encounters Monet, A. K. B. ; Stone, R. C. ; Monet, D. G. ; Dahn, C. C. ; Harris, H. C. ; Leggett, S. K. ; Pier, J. R. ; Vrba, F. J. ; Walker, R. L. Abstract Optical Charge Coupled Device (CCD) astrometry was done at the U.S. Naval Observatory Flagstaff Station (NOFS) to obtain positions of solar system bodies to be encountered by the Galileo spacecraft. The objects observed were the minor planets 951 Gaspra and 243 Ida, discussed in this paper, and the Galilean satellites of Jupiter, to be discussed in Paper II. Observations of Gaspra were made from April through August 1991, and Ida was observed from 1991 November through 1993 May. Each observing campaign was followed by a successful encounter. The instrumentation, techniques, analysis methods, and astrometric results are described. Publication: The Astronomical Journal Pub Date: June 1994 DOI: 10.1086/117036 Bibcode: 1994AJ....107.2290M Keywords: Asteroids; Astrometry; Astronomical Observatories; Charge Coupled Devices; Galileo Spacecraft; Astronomical Catalogs; Very Long Base Interferometry; Astronomy; MINOR PLANETS; SPACE PROBES full text sources ADS |

Single line CCD camera to improve positioning

This article describes an opto-electronic device that allows on-line visualization of the optical intensity function along a strip. The use of a linear optical charge-coupled device (CCD) array eliminates all moving parts. This makes adaptation to a standard microscope possible without modifications. The setup described here is essential where precise positioning of a reference graticule on diffuse lines must be performed.