KEYWORDS: Databases, Data storage, Data archive systems, Visualization, Human-machine interfaces, Astronomy, Radio astronomy, Data processing, System integration, Telescopes
The immense scale of data from modern radio interferometer arrays results in processing demands requiring HPC facilities to produce scientific results. However, in the modern era such facilities are more complex than a single monolithic HPC system. The transfer and processing of scientific data must be managed across hierarchies of storage and processing architectures; including traditional HPC, heterogeneous HPC, database and visualisation systems. The ICRAR Data Intensive Research Pathfinder (DIRP) will consist of an integrated system of the hardware, middleware, tools and interfaces to support ICRAR data intensive research primarily focused on data owing from the Australian SKA Pathfinder (ASKAP1) and the Murchison Widefield Array (MWA) telescopes.
KEYWORDS: Telescopes, Observatories, Data processing, Data archive systems, Process control, Calibration, Databases, Large telescopes, Astronomical telescopes, Astronomy
The ESO Very Large Telescope (VLT) started operations on Cerro Paranal (Chile) in April 1999 with one Unit Telescope and two science instruments. Seven years later it is still a growing facility consisting of four 8.2-m telescopes, three auxiliary telescopes for interferometry, and 11 science instruments. In addition two dedicated survey telescopes with wide-field cameras, VST and VISTA, a fourth auxiliary telescope, and several new instruments will become available in the coming months. Since the very beginning, VLT operations were planned to contain a substantial component of Service Mode observing, amounting to approximately 50% of the available time. The success of the full-scale implementation of Service Mode operations is reflected nowadays by the steady increase in its demand by the community, both in absolute terms and also relative to the demand in Visitor Mode, by the highly positive feedback received from the users, and also by the increasing flow of scientific results produced by programs that have exploited the unique advantages of flexible short-term scheduling. It is also fulfilling the requirement of creating a science archive and populating it with a data stream having through a quality control process. Here we review the current status of Service Mode observing at the VLT and the VLT Interferometer (VLTI), the challenges posed by its implementation on a wide variety of instrument modes, and its strong requirement of an integrated, end-to-end approach to operations planning with adequate tools and carefully defined policies and procedures. The experience of these seven years of VLT operations have led to a thorough exploration of operations paradigms that will be essential to the scientific success of ALMA and the extremely large optical telescopes in the coming decades.
The International Virtual Observatory Alliance (IVOA: http://www.ivoa.net) represents 14 international projects working in coordination to realize the essential technologies and interoperability standards necessary to create a new research infrastructure for 21st century astronomy. This international Virtual Observatory will allow astronomers to interrogate multiple data centres in a seamless and transparent way, will provide new powerful analysis and visualisation tools within that system, and will give data centres a standard framework for publishing and delivering services using their data. The first step for the IVOA projects is to develop the standardised framework that will allow such creative diversity. Since its inception in June 2002, the IVOA has already fostered the creation of a new international and widely accepted, astronomical data format (VOTable) and has set up technical working groups devoted to defining essential standards for service registries, content description, data access, data models and query languages following developments in the grid community. These new standards and technologies are being used to build science prototypes, demonstrations, and applications, many of which have been shown in international meetings in the past two years. This paper reviews the current status of IVOA projects, the priority areas for technical development, the science prototypes and planned developments.
KEYWORDS: Observatories, Astronomy, Standards development, Data centers, Data storage, Data archive systems, Astronomical imaging, Prototyping, Web services, Astronomical telescopes
The Astrophysical Virtual Observatory Project (AVO: http://www.eso.org/projects/avo/) will conduct a research and demonstration program on the scientific requirements and technologies necessary to build a VO for European astronomy. The AVO has been jointly funded by the European Commission and six European organizations for a three year Phase-A work program valued at 5 million Euro. The Phase A program will focus its work in three areas -- science requirements, archive interoperability and GIRD/database technologies. The AVO project, the US NVO and UK ASTROGRID projects have been working closely together over the past nine months to reach consensus on essential technical directions and standards that will facilitate the possibility of an International Virtual Observatory. An International Virtual Observatory Alliance was formed in June 2002 among all currently funded and proposed VO projects. The IVOA has adopted a roadmap for IVO developments over the next three years that will feature coordinated demonstrations of VO capabilities on specific science programs, and international agreements on key interoperability standards and tools.
KEYWORDS: Interferometry, Telescopes, Interferometers, Calibration, Visibility, Data archive systems, Data processing, Observatories, Signal processing, Space telescopes
In this article we present the Data Flow System (DFS) for the Very Large Telescope Interferometer (VLTI). The Data Flow System is the VLT end-to-end software system for handling astronomical observations from the initial observation proposal phase through the acquisition, processing and control of the astronomical data. The Data Flow system is now in the process of installation and adaptation for the VLT Interferometer. The DFS was first installed for VLTI first fringes utilising the siderostats together with the VINCI instrument and is constantly being upgraded in phase with the VLTI commissioning. When completed the VLT Interferometer will make it possible to coherently combine up to three beams coming from the four VLT 8.2m telescopes as well as from a set of initially three 1.8m Auxiliary Telescopes, using a Delay Line tunnel and four interferometry instruments. Observations of objects with some scientific interest are already being carried out in the framework of the VLTI commissioning using siderostats and the VLT Unit Telescopes, making it possible to test tools under realistic conditions. These tools comprise observation preparation, pipeline processing and further analysis systems. Work is in progress for the commissioning of other VLTI science instruments such as MIDI and AMBER. These are planned for the second half of 2002 and first half of 2003 respectively. The DFS will be especially useful for service observing. This is expected to be an important mode of observation for the VLTI, which is required to cope with numerous observation constraints and the need for observations spread over extended periods of time.
KEYWORDS: Telescopes, Data archive systems, Standards development, Observatories, Data storage, Interferometry, Astronomy, Fourier transforms, Digital video discs, Calibration
The end-to-end operations of the ESO VLT has now seen three full years of service to the ESO community. During that time its capabilities have grown to four 8.2m unit telescopes with a complement of four optical and IR multimode instruments being operated in a mixed Service Mode and Visitor Mode environment. The input and output of programs and data to the system is summarized over this period together with the growth in operations manpower. We review the difficulties of working in a mixed operations and development environment and the ways in which the success of the end-to-end approach may be measured. Finally we summarize the operational lessons learned and the challenges posed by future developments of VLT instruments and facilities such as interferometry and survey telescopes.
The VLT Data Flow System (DFS) has been developed to maximize the scientific output from the operation of the ESO observatory facilities. From its original conception in the mid 90s till the system now in production at Paranal, at La Silla, at the ESO HQ and externally at home institutes of astronomers, extensive efforts, iteration and retrofitting have been invested in the DFS to maintain a good level of performance and to keep it up to date. In the end what has been obtained is a robust, efficient and reliable 'science support engine', without which it would be difficult, if not impossible, to operate the VLT in a manner as efficient and with such great success as is the case today. Of course, in the end the symbiosis between the VLT Control System (VCS) and the DFS plus the hard work of dedicated development and operational staff, is what made the success of the VLT possible. Although the basic framework of DFS can be considered as 'completed' and that DFS has been in operation for approximately 3 years by now, the implementation of improvements and enhancements is an ongoing process mostly due to the appearance of new requirements. This article describes the origin of such new requirements towards DFS and discusses the challenges that have been faced adapting the DFS to an ever-changing operational environment. Examples of recent, new concepts designed and implemented to make the base part of DFS more generic and flexible are given. Also the general adaptation of the DFS at system level to reduce maintenance costs and increase robustness and reliability and to some extend to keep it conform with industry standards is mentioned. Finally the general infrastructure needed to cope with a changing system is discussed in depth.
The Data Flow System is the VLT end-to-end system for handling astronomical observations from the initial observation proposal phase through the acquisition, processing and control of the astronomical data. The VLT Data Flow System has been in place since the opening of the first VLT Unit Telescope in 1998. When completed the VLT Interferometer will make it possible to coherently combine up to three beams coming from the four VLT 8.2m telescopes as well as from a set of initially three 1.8m Auxiliary Telescopes, using a Delay Line tunnel and four interferometry instruments. The Data Flow system is now in the process of installation and adaptation for the VLT Interferometer. Observation preparation for a multi-telescope system, handling large data volume of several tens of gigabytes per night are among the new challenges offered by this system. This introduction paper presents the VLTI Data Flow system installed during the initial phase of VLTI commissioning. Observation preparation, data archival, and data pipeline processing are addressed.
KEYWORDS: Calibration, Data archive systems, Telescopes, Observatories, Data storage, Digital video discs, Data processing, Databases, Compact discs, Software development
On 1 April 1999, the first unit telescope (ANTU) of the ESO VLT began science operations. Two new instruments (FORS-1 for optical imaging and spectroscopy and ISAAC for IR imaging and spectroscopy) were offered in a mix of 50% visitor mode and 50% service mode. A Phase-I and Phase-II proposal and observation preparation process was conducted from 1 October 1998 until the middle of March 1999 involving approximately 280 proposals. A total of 1768 Observation Blocks for 83 approved service mode programs were scheduled and executed between 1 April and 1 October 1999. The resultant raw science and calibration data were subjected to quality control in Garching and released to the ESO user community starting from 15 June 1999 along with pipeline processed data products for a subset of instrument modes. The data flow loop for the first LT telescope is closed. The current operational VLT data flow system and the developments for the remainder of the VLT will be presented in the light of the first year of operational experience.
KEYWORDS: Data archive systems, Calibration, Telescopes, Virtual colonoscopy, Control systems, Digital micromirror devices, Data storage, Prototyping, Astronomy, Space telescopes
In order to realize the optimal scientific return from the VLT, ESO has undertaken to develop an end-to-end data flow system from proposal entry to science archive. The VLT Data Flow System (DFS) is being designed and implemented by the ESO Data Management and Operations Division in collaboration with VLT and Instrumentation Divisions. Tests of the DFS started in October 1996 on ESO's New Technology Telescope. Since then, prototypes of the Phase 2 Proposal Entry System, VLT Control System Interface, Data Pipelines, On-line Data Archive, Data Quality Control and Science Archive System have been tested. Several major DFS components have been run under operational conditions since February 1997. This paper describes the current status of the VLT DFS, the technological and operational challenges of such a system and the planing for VLT operations beginning in early 1999.
The MACHO experiment is searching for dark matter in the halo of the Galaxy by monitoring more than 50 million stars in the LMC, SMC, and Galactic bulge for gravitational microlensing events. The hardware consists of a 50 inch telescope, a two-color 32 megapixel ccd camera and a network of computers. On clear nights the system generates up to 8 GB of raw data and 1 GB of reduced data. The computer system is responsible for all realtime control tasks, for data reduction, and for storing all data associated with each observation in a database. The subject of this paper is the software system that handles these functions. It is an integrated system controlled by Petri nets that consists of multiple processes communicating via mailboxes and a bulletin board. The system is highly automated, readily extensive, and incorporates flexible error recovery capabilities. It is implemented with C++ in a Unix environment.
Science operations at the ESO very large telescope is scheduled to begin in April 1999. ESO is currently finalizing the VLT science operations plan. This plan describes the operations tasks and staffing needed to support both visitor and service mode operations. The Data Flow Systems (DFS) currently being developed by ESO will provide the infrastructure necessary for VLT science operations. This paper describes the current VLT science operations plan, first by discussing the tasks involved and then by describing the operations teams that have responsibility for those tasks. Prototypes of many of these operational concepts and tools have been in use at the ESO New Technology Telescope (NTT) since February 1997. This paper briefly summarizes the status of these prototypes and then discusses what operation lessons have been learned from the NTT experience and how they can be applied to the VLT.
The data flow system (DFS) for the ESO VLT provides a global system approach to the flow of science related data in the VLT environment. It includes components for preparation and scheduling of observations, archiving of data, pipeline data reduction and quality control. Standardized data structures serve as carriers for the exchange of information units between the DFS subsystems and VLT users and operators. Prototypes of the system were installed and tested at the New Technology Telescope. They helped us to clarify the astronomical requirements and check the new concepts introduced to meet the ambitious goals of the VLT. The experience gained from these tests is discussed.
A new optical immunoassay scheme based on surface second harmonic generation (SHG) is proposed. The utility of the technique has been investigated by deposition of sample antigen and antibody (bovine serum albumin & mouse anti-bovine serum albumin IgG antibody) on glass surfaces. The laser-induced second harmonic signals generated from these sample surfaces were monitored using a photomultiplier tube (Thorn EMI, 9524A). The surface second harmonic generation characteristics of an enzyme-linked immunoassay process were investigated, which is parallely monitored by a conventional ELISA method. The SSHG immunoassay experiment was performed using a conventional sandwich immunoassay scheme on ELISA immunoassay plates. The laser-induced surface-second harmonic signals generated from sample wells of different populations of the antigen-antibody complex were subsequently measured using the photomultiplier tube. To verify the new SSHG immunoassay results, a conventional ELISA sandwich immunoassay was performed, and their results compared. The new SSHG immunoassay results showed a virtually identical conclusion as that of conventional ELISA sandwich immunoassay. The SSHG readings are promotional to that of the ELISA data. However, the readings from the new SSHG immunoassay were found much larger, which is in agreement with the theoretical expectation. In this paper, detailed experimental results of the new SSHG immunoassay are described, and subsequently compared with those of a conventional ELISA immunoassay. The feasibility and advantages of the SSHG as a new immunoassay technique also are discussed.
A photomultiplier tube gain-suppression technique has been applied to a Thorn EMMI 9828B red sensitive photomultiplier. The gain-suppression mechanism and characteristics has been studied by measurement of the output changes of the photomultiplier during the application of the gain-suppression pulse while subjected to a constant incident light. Experimental results show that the 9828B photomultiplier tube can provide, at least, a two-step gain response for a constant incident light, when the gain-suppression pulse satisfies certain conditions. The application of the multiple-gain response of the PMT for the simultaneous measurement of photoluminescence of molecules of biological/biomedical importance is discussed.
This paper describes a remotely controlled, in-situ pH sensor by measuring the absorption change of an optical waveguide loaded with benzopurpurin 4B solutions. The theoretical evaluation is given for the sensitivity of TE and TM mode. The advantages of this sensor are as follows: (1) a liquid flow indicator avoids any irreversible effects; (2) waveguides generate a uniform evanescent field to provide a long stable reaction length. The TE mode shows better sensitivity than that of the TM mode for this sensor. It has a sensitivity of +/- 0.01 pH and a dynamic range of pH value 2.38 to 6.28.
Ca2+-activated adenosine triphosphatase isolated from rabbit muscle sarcoplasmic reticulum has been specifically labelled at a single lysine located at the putative ATP binding site with the triplet probe, eosin-5'-isothiocyanate. Labelled microsomes were suspended in buffer containing different cations to shift the enzyme to one or the other of its conformeric states, denoted E1 and E2. Samples in the different conformations were excited with a short laser pulse from a frequency doubled Nd:YAG laser. The time-resolved phosphorescence of the protein-bound probe was measured using a microcomputer-based dual- channel phosphorimeter over a temperature span of 2 degree(s) - 42 degree(s) C, and the emission anisotropy computed. The study suggests that in both conformeric states, the enzyme consists of different protein aggregates, however, the relative population of different protein aggregates may be different with the E2 form of the ATPase tending to form aggregates of larger size and the E1 form of the enzyme tending to form smaller aggregates. A more precise estimation of the sizes of the protein rotating species depends on accurate determination of the orientation of the label on the protein molecules.
We have developed an astronomical imaging system that incorporates a total of eight 2048 X 2048 pixel CCDs into two focal planes, to allow simultaneous imaging in two colors. Each focal plane comprises four 'edge-buttable' detector arrays, on custom Kovar mounts. The clocking and bias voltage levels for each CCD are independently adjustable, but all the CCDs are operated synchronously. The sixteen analog outputs (two per chip) are measured at 16 bits with commercially available correlated double sampling A/D converters. The resulting 74 MBytes of data per frame are transferred over fiber optic links into dual-ported VME memory. The total readout time is just over one minute. We obtain read noise ranging from 6.5 e- to 10 e- for the various channels when digitizing at 34 Kpixels/sec, with full well depths (MPP mode) of approximately 100,000 e- per 15 micrometers X 15 micrometers pixel. This instrument is currently being used in a search of gravitational microlensing from compact objects in our Galactic halo, using the newly refurbished 1.3 m telescope at the Mt. Stromlo Observatory, Australia.
Phosphorescence anisotropy measurements have been proposed as a method of following immunological reactions. To assess the utility of the technique, bovine serum albumin (BSA) has been employed as an antigen and its motion detected by covalently labelling the protein with the triplet probe, eosin-5'-isothiocyanate. A monoclonal IgG anti-BSA antibody was added to a solution of the labelled antigen thereby creating a heterogeneous population of rotating species of different sizes. The rotational mobilities of the labelled antigen and the labelled antigen-antibody complex have been examined by measurement of time-resolved phosphorescence depolarization of the probe, excited by a brief laser pulse from a frequency-doubled Nd:YAG laser. The orthogonally-polarized emission components were collected simultaneously and the time-resolved phosphorescence anisotropy (r(t)) calculated using a Marquardt curve fitting procedure. In the initial experiment, the time-resolved anisotropy from each antigen-antibody mixture was found to consist of more than one exponential decay process. The initial anisotropy values r(O) were found to be population dependent. The initial anisotropy values r(O) obtained from the phosphorescence decay measurements were relatively small (less than 0.07), however it can be enhanced by conjugating one of the species to a relatively large polymer bead. The experimental results indicate that the time-resolved phosphorescence depolarization could be exploited to study the kinetics of antigen and antibody interaction. There is also scope for development of the method for optical immunoassay.
Purified Na+, -adenosine triphosphatase (ATPase) in membrane vesicles has been covalently labelled with the triplet probe eosin S'-isothiocynate. The rotational mobility of the protein has been investigated by measurement of time-resolved depolarization of the emitted phosphorescence, induced by a laser pulse. The probe was specifically attached to a lysine residue of the protein located at the putative ATP binding site. The anisotropy of the emission was recorded over the temperature range 3°-42 °c. The total anisotropy was found to be temperature dependent with an initial value of about 0.2 at 3 °c and about 0.13 at 42 °C. The overall decrease of total anisotropy with temperature reversed in the temperature range around 13 °C where a peak value of total anisotropy was observed. The anisotropy decay curve was found to fit a double exponential decay process composed of a rapidly rotating component with a rotational correlation time of 20µs-10µs and a slower rotating component with a rotational correlation time of 400µs-100µs, over the temperature range of 3 °C-42 °C. These motions areindividually assigned to the motions of the monomer and oligomer states of the protein molecules, rotating about its axis normal to the plane of the membrane. It was also found that the associated weighting functions were also temperature-dependent; the weighting function of the slowly rotating species increases with increase in temperature, while the weighting function of the rapidly rotating species exhibits the opposite trend. It was estimated that about 80% of the total anisotropy signal was contributed by the fast rotation, and the remainder from slow rotation at 3°C and this reduced to 60% at 42°C.
A technique for the sequential measurement of fluorescence and phosphorescence depolarization is reported. The technique is based on a newly developed photomultiplier gain-suppression technique. The gain-suppression characteristics of the circuit are studied by applying a constant level of incident light. To demonstrate this new technique, a solid sample ofthetriplet probe eosin is excited by a pulsed, frequency-doubled Nd:YAG laser; the resulting orthogonally polarized emissions are collected by two balanced photomultipliers (PMT5). The gains of the PMTs are suppressed for the duration of the fluorescence emission, and subsequently returned to normal, to maintain the fluorescence and phosphorescence signals at the same level. The suppression of the gain is controlled by a specially designed dual-channel PMT gain-suppression circuit. The signals from the PMTs are recorded by two digital oscilloscopes, one set at a fast sampling rate to measure the static fluorescence anisotropy, the other set at a slow sampling rate to measure the slow phosphorescence depolarization. The anisotropy values can then be deduced from the two sets of recordings.
The Na+, K+-adenosine triphosphatase (ATPase) in microsomal membrane vesicles is covalently labeled with the triplet probe eosin 5'-isothiocyanate. Rotational mobility of the protein is investigated by measuring the time-resolved depolarization of the emitted phosphorescence from the triplet state of eosin, induced by a laser pulse. The probe is attached either nonspecifically to the protein or under conditions where the eosin is attached specifically to a lysine residue located atthe putative ATP binding site. The total anisotropy of the emission is found to be almost constant when measured over the temperature range 10 to 25°C. The anisotropy value is relatively small when the label is bound nonspecifically to the binding sites of the protein, but markedly increases when specifically bound to the protein, suggesting that the independent motion of the probe is constrained at this site. The anisotropy decay curve obtained from the specifically labeled protein shows a clearly biphasic character, and is composed of a rapidly rotating component with a rotational correlation time of 20 to 5 μs and a slower rotating component with a rotational correlation time of 250 to 90 μs in the temperature range 10 to 25°C. These motions are individually assigned to the segmental motion of the polypeptide chain and rotation of the whole protein about its axis normal to the plane of the membrane, respectively. It is estimated that about 80% ofthe total anisotropy signal is contributed by the fast rotation, and the remainder results from slow rotation.
A newly developed dual-channel time domain phosphorimeter is described in this paper. This employs a pulsed, frequency doubled Nd:YAG laser as a linear polarized pumping source. The resulting orthogonally polarized emission components are then simultaneously collected by two oppositely positioned photomultiplier tubes (PMTs), digitized by a digital storage adaptor, and then transferred to an IBM PC microcomputer where the intensity or the depolarization (anisotropy) of the emission is calculated. The range of lifetimes or rotational correlation times that can be routinely determined with this instrument extends from a few microseconds to milliseconds. The instrument has an 8 bit magnitude resolution and a signal sampling rate of 20 mesa-samples per second. The averaging function of the instrument yields a single measurement with an average of over 2 to 255 excitation transients. To demonstrate the utility of the new instrument, studies of the emission properties of the triplet probe eosin immobilized in a polymer matrix and covalently bound to a membrane protein are reported.
The Na+, K+-adenosine triphosphatase (ATPase) in microsomal membrane vesicles has been covalently labeled with the triplet probe eosin 5'- isothiocynate. Rotational mobility of the protein has been investigated by measurement of time-resolved depolarization of the emitted phosphorescence from the triplet state of eosin, induced by a laser pulse. The probe was attached non-specifically to the protein and under conditions where the eosin was attached specifically to a lysine residue located at the putative ATP binding site. The total anisotropy of the emission was found to be almost constant when measured over the temperature range 10 degree(s)C - 25 degree(s)C. The anisotropy value was relatively small when the label was bound non-specifically to the binding sites of the protein, but was markedly increased when specifically bound to the protein, suggesting that the independent motion of the probe was constrained at this site. The anisotropy decay curve obtained from the specifically labeled protein shows a clearly biphase character, and is composed of a rapidly rotating component with a rotational correlation time of 20 microsecond(s) - 5microsecond(s) and a slower rotating component with a rotational correlation time of 250 microsecond(s) - 90microsecond(s) , the temperature range over 10 degree(s)C - 25 degree(s)C. These motions are individually assigned to the segmental motion of the polypeptide chain and the whole protein rotating about its axis normal to the plane of the membrane. It was estimated that about 80% of the total anisotropy signal was contributed by the fast rotation, and the remainder from slow rotation.
A new technique for the simultaneous measurement of fluorescence and phosphorescence depolarization is reported. The technique is based on a newly developed photomultiplier gain suppression technique. The gain suppression characteristics of the circuit were studied by applying a constant level of incident light. To demonstrate this new technique, a solid sample of the triplet probe eosin was excited by a pulsed, frequency doubled Nd:YAG laser; the resulting orthogonally-polarized emissions were collected by two balanced photomultiplier (PMTs). The gains of the PMTs were suppressed for the duration of the fluorescence emission, and subsequently returned to normal, in order to keep the measured fluorescence and phosphorescence signals at the same level. The suppression of the gain was controlled by using a specially designed dual-channel PMT gain suppression circuit. The signals from the PMTs were recorded by two digital oscilloscopes, one set at a fast sweep time in order to measure the transient fluorescence depolarization and the other set at a slow sweep time in order to measure the slow phosphorescence depolarization. The anisotropies can then be deduced from the two sets of recordings.
The slow rotational diffusion of macromolecules has been investigated by measuring the decay of dichroism in laser-pulse induced transient emissions for triplet probes bound to the molecules. A comparison of the anisotropy parameters of phosphorescence and delayed fluorescence from eosin-bound bovine serum albumin (BSA) is described. The results indicate that the measurement of delayed fluorescence is often the preferable option for investigating the rotational diffusion of the macromolecules.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.