SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Nine specific techniques of combination of techniques developed for applying digital image processing technology to existing astronomical imagery are described. Photoproducts are included to illustrate the results of each of these investigations.
In this paper, we present a new algorithm for estimating the Point Spread Function (PSF) in wide-field astronomical images with extreme source crowding. Robust and accurate PSF estimation in crowded astronomical images dramatically improves the fidelity of astrometric and photometric measurements extracted from wide-field sky monitoring imagery. Our radically new approach utilizes convolutional sparse representations to model the continuous functions involved in the image formation. This approach avoids the need to detect and precisely localize individual point sources that is shared by existing methods. In experiments involving simulated astronomical imagery, it significantly outperforms the recent alternative method with which it is compared.
Techniques for using image processing in astronomy are identified and developed for the following: (1) geometric and radiometric decalibration of vidicon-acquired spectra, (2) automatic identification and segregation of stars from galaxies; and (3) display of multiband radio maps in compact and meaningful formats. Examples are presented of these techniques applied to a variety of objects.
Several areas of applications of image processing to astronomy were identified and discussed. These areas include: (1) deconvolution for atmospheric seeing compensation; a comparison between maximum entropy and conventional Wiener algorithms; (2) polarization in galaxies from photographic plates; (3) time changes in M87 and methods of displaying these changes; (4) comparing emission line images in planetary nebulae; and (5) log intensity, hue saturation intensity, and principal component color enhancements of M82. Examples are presented of these techniques applied to a variety of objects.
Topics include: (1) polar coordinate transformations (M83); (2) multispectral ratios (M82); (3) maximum entropy restoration (M87); (4) automated computation of stellar magnitudes in nebulosity; (5) color and polarization; (6) aliasing.
The eye as an efficient selection device for determining what is important in astronomical imagery can be greatly aided by the computer. A suitable facility, called the Interactive Astronomical Data Analysis Facility (IADAF), has been developed for the display and analysis of astronomical imagery by the Laboratory for Astronomy and Solar Physics. The Laboratory for Astronomy and Solar Physics currently has approval to fly two experiments on Spacelab. The Solar Extreme Ultraviolet Telescope (SEUTS) is to be used for the study of several fundamental problems of solar physics. The Ultraviolet Image Telescope for Astronomical Investigations (UIT) is to provide direct imagery of selected fields of view throughout the sky. A description is given of IADAF, taking into account its 16-bit computer and the COMTAL image processing display system. The use of IADAF by SEUTS and UIT is discussed.
General objectives of space astronomical imagery are briefly examined, taking into account the improved angular resolution achievable in space observations, the utilization of an accessibility of the far ultraviolet spectral range for an easier detection and more accurate measurement of very hot stars, the determination of the structure and evolution of galaxies, and the determination of the cosmic distance scale. Attention is given to the Ultraviolet Imaging Telescope, the Spacelab Wide Angle Telescope, and the Starlab UV/optical telescope facility. It is pointed out that Starlab is envisioned as a multi-instrument, multi-purpose astronomical facility based on a near-diffraction-limited Ritchey-Chretien telescope of about 1 meter aperture and f/15 focal ratio. These resolutions are a factor of 10 better than typically achieved with ground-based telescopes.
The status of the current microdensitometers used for digitizing astronomical imagery is discussed. The tests and improvements that have and can be made to the Photometric Data System PDS microdensitometer are examined. The various types of microdensitometers that currently exist in the world are investigated. Papers are presented on the future needs and the data processing problems associated with digitizing large images.
The status of laboratory and telescope tests of integrated infrared detector array technology for astronomical applications is described. The devices tested represent a number of extrinsic and intrinsic detector materials and various multiplexer designs. Infrared arrays have now been used in successful astronomical applications. These have shown that device sensitivities can be comparable to those of discrete detector systems and excellent astronomical imagery can be produced.
Programs are now underway to develop and demonstrate the detector/array technology needed for the Space Infrared Telescope Facility (SIRTF), Large Deployable Reflector (LDR), and other future NASA missions. The development goal is to achieve focal plane sensitivities, at extended integration times over the 2 to 700 microns range, limited only by the low astrophysical backgrounds encountered in cryogenic telescopes such as SIRTF. Dramatic progress has been made in the last 2 to 3 years in integrated array and detector systems for low background astronomical applications. With the broadly based developments and lab characterizations now underway for SIRTF and similar space applications, coupled with the rapidly expanding art and science of ground based astronomical imagery with arrays, the potential for effective utilization of arrays with LDR appears to be very good.
The status of a program which develops and characterizes integrated infrared (IR) detector array technology for space astronomical applications is described. The devices under development include intrinsic, extrinsic silicon, and extrinsic germanium detectors, coupled to silicon readout electronics. Low-background laboratory test results include measurements of responsivity, noise, dark current, temporal response, and the effects of gamma-radiation. In addition, successful astronomical imagery has been obtained on some arrays from this program. These two aspects of the development combine to demonstrate the strong potential for integrated array technology for IR space astronomy.
The SkyView Virtual Telescope allows users to query over 75 distinct datasets of astronomical imagery including more than 190 distinct surveys. These holdings are extraordinarily diverse ranging over more than 15 orders of magnitude in frequency and5 orders of magnitude in resolution. To accommodate supporting these data, SkyView has developed a simple data model for surveys. Nor surprisingly, given the diverse origins of the datasets included, some surveys do not easily fit within this model. The conventional approach to dealing with such outliers is to build a layer on top of the actual data which more faithfully adheres to the data model. With SkyView we have used a somewhat alternative approach. We allow the data model to define new behaviors in the SkyView code itself either by customizing the use of existing capabilities or pointing to new classes that have non-standard behavior. This approach is feasible since in modern computer languages the code that is run can be selected dynamically with new classes completely overriding traditional behavior. This paper describes this approach and considers how it may become more useful as our software structures become increasingly dynamically linked.
The STScI optical disk project was designed to explore the options, opportunities and problems presented by the optical disk technology, and to see if optical disks are a viable, and inexpensive, means of storing the large amount of data which are found in astronomical digital imagery. A separate workstation was purchased on which the development can be done and serves as an astronomical image processing computer, incorporating the optical disks into the solution of standard image processing tasks. It is indicated that small workstations can be powerful tools for image processing, and that astronomical image processing may be more conveniently and cost-effectively performed on microcomputers than on the mainframe and super-minicomputers. The optical disks provide unique capabilities in data storage.
A large astronomical telescope, termed the Space Telescope, is expected to be placed in orbit in the early 1980's. It will be operated as an international observatory that will enable astronomers to detect electromagnetic radiation over a much broader spectrum than is possible from ground observatories. The image quality (not degraded by atmospheric effects) will be limited only by the quality of the optics and by aperture diffraction. This opportunity to approach diffraction-limited imagery on an astronomical telescope of this size (2.4-m aperture) sets unusually stringent tolerances on the optical quality. The budgeting and control of these qualities throughout the design, fabrication, assembly, and operation of the Space Telescope is described. A feedback control system which will maintain the telescope at peak performance in the orbital environment is examined.
Stratospheric Observatory for Infrared Astronomy, or SOFIA, is the new generation airborne observatory station based at NASA s Dryden Aircraft Operations Facility, Palmdale, CA, to study the universe. Since the observatory detects infrared energy, water vapor is a concern in the atmosphere due to its known capacity to absorb infrared energy emitted by astronomical objects. Although SOFIA is hoping to fly above 99% of water vapor in the atmosphere it is still possible to affect astronomical observation. Water vapor is one of the toughest parameter to measure in the atmosphere, several atmosphere modeling are used to calculate water vapor loading. The water vapor loading, or Precipitable water, is being calculated by Matlab along the planned flight path. Over time, these results will help SOFIA to plan flights to regions of lower water vapor loading and hopefully improve the imagery collection of these astronomical features.
It has been known for some time that glancing incidence X-ray optics have sharply peaked point response functions. The spatial resolution of Wolter X-ray telescope systems is frequently limited by the performance characteristics of the X-ray detector rather than by the optics, even when high resolution detectors such as photographic emulsions are used. This problem becomes even more severe when it is desirable to take advantage of the high sensitivity and broad wavelength response afforded by modern solid state detectors such as charge coupled devices or multi-anode microchannel arrays. Results of theoretical investigations of methods for increasing the telescope plate scale by the use of glancing incidence hyperboloid/ellipsoid X-ray microscope optics and normal incidence contoured layered synthetic microstructure optics for coupling the Wolter mirrors to the detector are reported. The relative merits of the different hybrid X-ray telescope systems which result will be discussed. Considerations will be made concerning applications of these systems to high resolution imagery and spectroscopy of astronomical X-ray/XUV sources.
The Hubble Space Telescope (HST) is designed to carry five major scientific instruments to collect imagery, spectrographic, and photometric astronomical data. The Pointing Control System is to achieve pointing accuracies and line of sight jitter levels an order of magnitude less than can be achieved with ground mounted telescopes. In addition, the HST must be able to acquire and track solar system targets with apparent motion up to 0.21 arcsec/s. Such targets include planetary satellites, planetary surface features and comets. It is to perform this tracking with an accuracy under 0.03 arcsec at the maximum rate. Tracking of solar objects by the Space Telescope accounts for the effects of velocity aberration and parallax, as well as solar targeting a celestial object in a science instrument aperture. The design of the Pointing Control System solar object tracking features is discussed, with emphasis on the special timing and granulation problems inherent with a sampled-data, multirate digital control system.
The Hubble Space Telescope (HST) is to carry five major scientific instruments to collect imagery, spectrographic, and photometric astronomical data. The Pointing Control System is designed to achieve pointing accuracies and line of sight jitter levels an order of magnitude less than can be achieved with ground mounted telescopes. This paper describes the operation of the pointing control system flight software in targeting a celestial object in a science instrument aperture and in performing the coordinate transformations necessary for commanding the fine guidance sensor and determining the attitude-error corrections.