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The Cryogenic Near-Infrared Spectro-Polarimeter (Cryo-NIRSP) is a combination slit-based spectrograph and context-imaging instrument designed and built for the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). It is optimized for polarimetric observations of spectral band-passes between 1 and 5 microns, which makes it uniquely suited for polarimetric observations of the solar corona, while also enabling access to other important infrared diagnostics such as the CO fundamental band at 4.6 microns. Integration, testing, and commissioning occurred between 2019 and 2020, and it is now conducting science experiments as part of DKIST early operations. In this article, we discuss its science mission, the requirements driving the design, its fabrication and installation, current capabilities, and the first science data.

The Cryogenic Near Infrared Spectropolarimeter (Cryo-NIRSP) data processing pipeline has been created to process the live data stream whilst on summit and supports the extensive variety of operational modes that the Cryo-NIRSP accommodates. It performs data processing, data storage, and the displaying of quality assurance measures. This includes tasks such as the derivation of calibration parameters, saving of master frames, data reduction, and demodulation. Significant work has also gone into the quality assurance aspect, which publishes the outputs to a display in real time for on-the-spot data verification. This provides the final element to the end-to-end running of the Cryo-NIRSP.

Construction of the Daniel K. Inouye Solar Telescope (DKIST) is well underway on the Haleakalā summit on the Hawaiian island of Maui. Featuring a 4-m aperture and an off-axis Gregorian configuration, the DKIST will be the world’s largest solar telescope. It is designed to make high-precision measurements of fundamental astrophysical processes and produce large amounts of spectropolarimetric and imaging data. These data will support research on solar magnetism and its influence on solar wind, flares, coronal mass ejections, and solar irradiance variability. Because of its large aperture, the DKIST will be able to sense the corona’s magnetic field—a goal that has previously eluded scientists—enabling observations that will provide answers about the heating of stellar coronae and the origins of space weather and exo-weather. The telescope will cover a broad wavelength range (0.35 to 28 microns) and operate as a coronagraph at infrared (IR) wavelengths. Achieving the diffraction limit of the 4-m aperture, even at visible wavelengths, is paramount to these science goals. The DKIST’s state-of-the-art adaptive optics systems will provide diffraction-limited imaging, resolving features that are approximately 20 km in size on the Sun. At the start of operations, five instruments will be deployed: a visible broadband imager (VTF), a visible spectropolarimeter (ViSP), a visible tunable filter (VTF), a diffraction-limited near-IR spectropolarimeter (DLNIRSP), and a cryogenic near-IR spectropolarimeter (cryo-NIRSP). At the end of 2017, the project finished its fifth year of construction and eighth year overall. Major milestones included delivery of the commissioning blank, the completed primary mirror (M1), and its cell. Commissioning and testing of the coude rotator is complete and the installation of the coude cleanroom is underway; likewise, commissioning of the telescope mount assembly (TMA) has also begun. Various other systems and equipment are also being installed and tested. Finally, the observatory integration, testing, and commissioning (IT&C) activities have begun, including the first coating of the M1 commissioning blank and its integration within its cell assembly. Science mirror coating and initial on-sky activities are both anticipated in 2018.

We provide an update on the construction status of the Daniel K. Inouye Solar Telescope. This 4-m diameter facility is designed to enable detection and spatial/temporal resolution of the predicted, fundamental astrophysical processes driving solar magnetism at their intrinsic scales throughout the solar atmosphere. These data will drive key research on solar magnetism and its influence on solar winds, flares, coronal mass ejections and solar irradiance variability. The facility is developed to support a broad wavelength range (0.35 to 28 microns) and will employ state-of-the-art adaptive optics systems to provide diffraction limited imaging, resolving features approximately 20 km on the Sun. At the start of operations, there will be five instruments initially deployed: Visible Broadband Imager (VBI; National Solar Observatory), Visible SpectroPolarimeter (ViSP; NCAR High Altitude Observatory), Visible Tunable Filter (VTF (a Fabry-Perot tunable spectropolarimeter); Kiepenheuer Institute for Solarphysics), Diffraction Limited NIR Spectropolarimeter (DL-NIRSP; University of Hawaii, Institute for Astronomy) and the Cryogenic NIR Spectropolarimeter (Cryo-NIRSP; University of Hawaii, Institute for Astronomy). As of mid-2016, the project construction is in its 4th year of site construction and 7th year overall. Major milestones in the off-site development include the conclusion of the polishing of the M1 mirror by University of Arizona, College of Optical Sciences, the delivery of the Top End Optical Assembly (L3), the acceptance of the Deformable Mirror System (Xinetics); all optical systems have been contracted and are either accepted or in fabrication. The Enclosure and Telescope Mount Assembly passed through their factory acceptance in 2014 and 2015, respectively. The enclosure site construction is currently concluding while the Telescope Mount Assembly site erection is underway. The facility buildings (Utility and Support and Operations) have been completed with ongoing work on the thermal systems to support the challenging imaging requirements needed for the solar research. Finally, we present the construction phase performance (schedule, budget) with projections for the start of early operations.

We provide a brief update on the construction status of the Daniel K. Inouye Solar Telescope, a $344M, 10-year construction project to design and build the world's largest solar physics observatory. We review the science drivers along with the challenges in meeting the evolving scientific needs over the course of the construction period without jeopardizing the systems engineering and management realization. We review the tools, processes and performance measures in use in guiding the development as well as the risks and challenges as the project transitions through various developmental phases. We elaborate on environmental and cultural compliance obligations in building in Hawai'i. We discuss the broad "lessons learned". Finally, we discuss the project in the context of the evolving management oversight within the US (in particular under the NSF).

It is a top level science requirement that data from the Daniel K Inouye Solar Telescope (DKIST) is archived and made available to the world wide astronomical community. Data from DKIST must contain sufficient meta-data to allow proper post processing. This paper describes how the Telescope Control System (TCS), Wavefront Correction Control System (WCCS) and individual instrument control systems work together with the camera systems to provide the world coordinate information (WCI) meta-data for 2-d imaging detectors.

The Daniel K. Inouye Solar Telescope (DKIST) will include facility instruments that perform polarimetric observations of the sun. In order for an instrument to successfully perform these observations its Instrument Controller (IC) software must be able to tightly synchronize the activities of its sub-systems including polarization modulators, cameras, and mechanisms. In this paper we discuss the DKIST control model for synchronizing these sub-systems without the use of hardware trigger lines by using the DKIST Time Reference And Distribution System (TRADS) as a common time base and through sub-system control interfaces that support configuring the timing and cadence of their behavior. The DKIST Polarization Modulator Controller System (PMCS) provides an interface that allows the IC to characterize the rotation of the modulator in terms of a reference time (t0), rate, and start state. The DKIST Virtual Camera (VC) provides a complimentary interface that allows data acquisitions and accumulation sequences to be specified using a reference time (t0), rate, and execution block time slices, which are cumulative offsets from t0. Re-configuration of other instrument mechanisms such as filter, slits, or steering mirrors during the observation is the responsibility of the IC and must be carefully scheduled at known and pre-determined gaps in the VC data acquisition sequence. The DKIST TRADS provides an IEEE-1588-2008 Precision Time Protocol (PTP) service that is used to synchronize the activities of instrument sub-systems. The modulator, camera, and mechanism sub-systems subscribe to this service and can therefore perform their tasks according to a common time base. In this paper we discuss the design of the PMCS, VC, and mechanism control interfaces, and how the IC can use them to configure the behavior of these sub-systems during an observation. We also discuss the interface to TRADS and how it is used as a common time base in each of these sub-systems. We present our preliminary results of the system performance against known instrument use cases.

The Advanced Technology Solar Telescope (ATST) is a 4-meter solar observatory under construction at Haleakala, Hawaii. The simultaneous use of multiple instruments is one of the unique capabilities that makes the ATST a premier ground based solar observatory. Control of the instrument suite is accomplished by the Instrument Control System (ICS), a layer of software between the Observatory Control System (OCS) and the instruments. The ICS presents a single narrow interface to the OCS and provides a standard interface for the instruments to be controlled. It is built upon the ATST Common Services Framework (CSF), an infrastructure for the implementation of a distributed control system. The ICS responds to OCS commands and events, coordinating and distributing them to the various instruments while monitoring their progress and reporting the status back to the OCS. The ICS requires no specific knowledge about the instruments. All information about the instruments used in an experiment is passed by the OCS to the ICS, which extracts and forwards the parameters to the appropriate instrument controllers. The instruments participating in an experiment define the active instrument set. A subset of those instruments must complete their observing activities in order for the experiment to be considered complete and are referred to as the must-complete instrument set. In addition, instruments may participate in eavesdrop mode, outside of the control of the ICS. All instrument controllers use the same standard narrow interface, which allows new instruments to be added without having to modify the interface or any existing instrument controllers.

As PLCs evolve from simple logic controllers into more capable Programmable Automation Controllers (PACs), observatories are increasingly using such devices to control complex mechanisms 1, 2 . This paper describes use of COTS software to control such hardware using the Advanced Technology Solar Telescope (ATST) Common Services Framework (CSF). We present the Enclosure Control System (ECS) under development in Spain and the UK. The paper details selection of the commercial PLC communication library PLCIO. Implemented in C and delivered with source code, the library separates the programmer from communication details through a simple API. Capable of communicating with many types of PLCs (including Allen-Bradley and Siemens) the API remains the same irrespective of PLC in use. The ECS is implemented in Java using the observatory's framework that provides common services for software components. We present a design following a connection-based approach where all components access the PLC through a single connection class. The link between Java and PLCIO C library is provided by a thin Java Native Interface (JNI) layer. Also presented is a software simulator of the PLC based upon the PLCIO Virtual PLC. This creates a simulator operating below the library's API and thus requires no change to ECS software. It also provides enhanced software testing capabilities prior to hardware becoming available. Results are presented in the form of communication timing test data, showing that the use of CSF, JNI and PLCIO provide a control system capable of controlling enclosure tracking mechanisms, that would be equally valid for telescope mount control.

The National Solar Observatory’s (NSO) Advanced Technology Solar Telescope (ATST) is the first large U.S. solar telescope accessible to the worldwide solar physics community to be constructed in more than 30 years. The 4-meter diameter facility will operate over a broad wavelength range (0.35 to 28 μm ), employing adaptive optics systems to achieve diffraction limited imaging and resolve features approximately 20 km on the Sun; the key observational parameters (collecting area, spatial resolution, spectral coverage, polarization accuracy, low scattered light) enable resolution of the theoretically-predicted, fine-scale magnetic features and their dynamics which modulate the radiative output of the sun and drive the release of magnetic energy from the Sun’s atmosphere in the form of flares and coronal mass ejections. In 2010, the ATST received a significant fraction of its funding for construction. In the subsequent two years, the project has hired staff and opened an office on Maui. A number of large industrial contracts have been placed throughout the world to complete the detailed designs and begin constructing the major telescope subsystems. These contracts have included the site development, AandE designs, mirrors, polishing, optic support assemblies, telescope mount and coude rotator structures, enclosure, thermal and mechanical systems, and high-level software and controls. In addition, design development work on the instrument suite has undergone significant progress; this has included the completion of preliminary design reviews (PDR) for all five facility instruments. Permitting required for physically starting construction on the mountaintop of Haleakalā, Maui has also progressed. This paper will review the ATST goals and specifications, describe each of the major subsystems under construction, and review the contracts and lessons learned during the contracting and early construction phases. Schedules for site construction, key factory testing of major subsystems, and integration, test and commissioning activities will also be discussed.

At future telescopes, adaptive optics systems will play a role beyond the correction of Earth's atmosphere. These systems are capable of delivering information that is useful for instrumentation, e.g. if reconstruction algorithms are employed to increase the spatial resolution of the scientific data. For the 4m aperture Advanced Technology Solar Telescope (ATST), a new generation of state-of-the-art instrumentation is developed that will deliver observations of the solar surface at unsurpassed high spatial resolution. The planned Visual Broadband Imager (VBI) is one of those instruments. It will be able to record images at an extremely high rate and compute reconstructed images close to the telescope's theoretical diffraction limit using a speckle interferometry algorithm in near real-time. This algorithm has been refined to take data delivered by the adaptive optics system into account during reconstruction. The acquisition and reconstruction process requires the use of a high-speed data handling infrastructure to retrieve the necessary data from both adaptive optics system and instrument cameras. We present the current design of this infrastructure for the ATST together with a feasibility analysis of the underlying algorithms.

The 4m Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope and the world's leading ground-based resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and variability in the Sun's output. The project has successfully passed its final design review and the Environmental Impact Study for construction of ATST on Haleakala, Maui, HI has been concluded in December of 2009. The project is now entering its construction phase. As its highest priority science driver ATST shall provide high resolution and high sensitivity observations of the dynamic solar magnetic fields throughout the solar atmosphere, including the corona at infrared wavelengths. With its 4 m aperture, ATST will resolve features at 0."03 at visible wavelengths and obtain 0."1 resolution at the magnetically highly sensitive near infrared wavelengths. A high order adaptive optics system delivers a corrected beam to the initial set of state-of-the-art, facility class instrumentation located in the coude laboratory facility. The initial set of first generation instruments consists of five facility class instruments, including imagers and spectropolarimeters. The high polarimetric sensitivity and accuracy required for measurements of the illusive solar magnetic fields place strong constraints on the polarization analysis and calibration. Development and construction of a fourmeter solar telescope presents many technical challenges, including thermal control of the enclosure, telescope structure and optics and wavefront control. A brief overview of the science goals and observational requirements of the ATST will be given, followed by a summary of the design status of the telescope and its instrumentation, including design status of major subsystems, such as the telescope mount assembly, enclosure, mirror assemblies, and wavefront correction

The high order adaptive optics (HOAO) system is the centerpiece of the ATST wavefront correction system. The ATST wavefront correction system is required to achieve a Strehl of S = 0.6 or better at visible wavelength. The system design closely follows the successful HOAO implementation at the Dunn Solar Telescope and is based on the correlating Shack-Hartmann wavefront sensor. In addition to HOAO the ATST will utilize wavefront sensors to implement active optics (aO) and Quasi Static Alignment (QSA) of the telescope optics, which includes several off-axis elements. Provisions for implementation of Multi-conjugate adaptive optics have been made with the design of the optical path that feeds the instrumentation at the coude station. We will give an overview of the design of individual subsystems of the ATST wavefront correction system and describe some of the unique features of the ATST wavefront correction system, such as the need for thermally controlled corrective elements.

The Advanced Technology Solar Telescope (ATST) Common Services Framework (CSF) provides the technical framework necessary to quickly and easily develop applications implementing the command-action-response model. The ATST Base builds on top of CSF and provides applications that, with a few modifications, can be dropped into a telescope control system or an instrument control system. This is done by extending the CSF Controller and writing applications that perform some of the common tasks needed by telescope and instrument control systems. This paper includes a general look at the Hardware Controller and an in-depth look at the Management Controller and Motion Controller classes. Telescope and instrument control systems typically have multiple axes of motion that need to be coordinated. Management Controllers allow a simple command to be given to a single Controller and then aggregated to multiple worker Controllers who can perform multiple actions. Management Controllers aggregate the state and status of their workers. The workers may be of the same type (e.g., multiple servo control systems) or of different types (e.g., two different servo controllers, a hexapod controller, digital I/O controller and a camera controller). Most users of turnkey motion control solutions use only a few of the commands that the motion control system provides. The ATST Base Motion Controller abstracts the hardware, and provides a simple interface (focusing on a few common instructions) to use in controlling different types of motion stages.

The 4m ATST will be the most powerful solar telescope in the world, providing a unique scientific tool to study the Sun and other astronomical objects. The design and development phase for the Advance Technology Solar Telescope (ATST) is progressing. The conceptual design review (CoDR) for the ATST is scheduled for August 2003. We present a brief description of the science requirements of ATST, and remind the reader of some of the technical challenges of building a 4-m solar telescope. We will discuss some of the design strategies that will allow us to achieve the required performance specifications, present conceptual designs for the ATST, and summarize the results of trades we have made on our path to the CoDR. The thermal impacts to local, self-induced seeing with respect to some of our system level trades that have been completed will be discussed.

The Advanced Technology Solar Telescope (ATST) has implemented a novel method for gathering header information on data products. At the time of data collection, the specific state of the telescope and instrumentation needs to be collected and associated with the saved data. The ATST performs this task by issuing a header request event across the ATST event system. All observatory software components that are registered for the event and are participating in the current experiment or observation report status information to a central header repository. Various types of header request events may be selected for start or stop of individual frames, groups of frames, or entire observations. The final data products are created by combining the data files with all or some of stored header information in the database. The resulting data file may be generated in any possible format, including FITS. Much of the implementation of this approach is integrated into the ATST technical framework, simplifying the development process for component writers and ensuring consistent responses to header request events.

The new observatories currently being built, upgraded or designed represent a big step up in terms of complexity (laser guide star, adaptive optics, 30/40m class telescopes) with respect to the previous generation of ground-based telescopes. Moreover, the high cost of observing time imposes challenging requirements on system reliability and observing efficiency as well as challenging constraints in implementing major upgrades to operational observatories. Many of the basic issues are common to most of the new projects, while each project also brings an additional set of very specific challenges, imposed by the unique characteristics and scientific objectives of each telescope. Finding ways to share the solution and the risk for these common problems would allow the teams in the different projects to concentrate more resources on the specific challenges, while at the same time realizing more reliable and cost efficient systems. In this paper we analyze the many dimensions that might be involved in sharing and re-using observatory software (e.g. components, design, infrastructure frameworks, applications, toolkits, etc.). We also examine observatory experiences and technology trends. This work is the continuation of an effort started in the middle of 2007 to analyze the trends in software for the control systems of large astronomy projects.

The paper discusses methods and strategies for designing software systems for modern observatories. The development of software continues to be a challenge for new projects, in areas ranging from budget and schedule to design and operations. Software systems can be challenging areas to plan and manage if effective methods are not undertaken early in a project. Software is itself a system, developed similarly to other, more classical systems. It may be distributed across many other systems, but it must function as a single, coordinated entity. It is process-oriented, executing a behavior consistent with its input parameters and delivering a desired outcome. It is based upon a unifying architectural concept and built around a common infrastructure. Understanding and implementing these characteristics early in the design stage allows software to develop efficiently, rather than evolving toward them in a semi-random walk.

When constructed on the summit of Haleakala on the island of Maui, Hawaii, the Advanced Technology Solar Telescope (ATST) will be the world's largest solar telescope. The ATST is a unique design that utilizes a state-of-the-art off-axis Gregorian optical layout with five reflecting mirrors delivering light to a Nasmyth instrument rotator, and nine reflecting mirrors delivering light to an instrument suite located on a large diameter rotating coude lab. The design of the telescope mount structure, which supports and positions the mirrors and scientific instruments, has presented noteworthy challenges to the ATST engineering staff. Several novel design solutions, as well as adaptations of existing telescope technologies to the ATST application, are presented in this paper. Also shown are plans for the control system and drives of the structure.

An important part of a large solar telescope is the ability to correct, in real time, optical alignment errors caused by gravitational bending of the telescope structure and wavefront errors caused by atmospheric seeing. The National Solar Observatory is currently designing the 4 meter Advanced Technology Solar Telescope (ATST). The ATST wavefront correction system, described in this paper, will incorporate a number of interacting wavefront control systems to provide diffraction limited imaging performance. We will describe these systems and summarize the interaction between the various sub-systems and present results of performance modeling.

ATST control systems communicate by passing sets of attribute-value pairs between system components. Each set, or configuration, defines a required state for a component to match. To coordinate the control systems using configurations, every component must implement a consistent behavior. The ATST Controller provides a base class for components to use that implements a uniform life cycle and functional behavior for matching configurations. The ATST Controller class is one of the key elements of the ATST Common Services software framework. The Controller class accepts input configurations though a simple command interface. The class is readily extended to subclasses that may perform detailed operations based on the configuration. Alternatively, ATST Controllers may be used in hierarchical systems that delegate actions to groups of lower level controllers. The Controller provides a simple configuration life cycle to determine the state of a configuration in a component. The Controller also enforces a separation of a component's command request and the ensuing action by executing each configuration in its own thread. This implementation also allows a Controller to execute simultaneous configurations, where the synchronization and exclusion details are left to the implementing subclass.

The Advance Technology Solar Telescope (ATST) has finished its conceptual design stage, submitted a proposal for construction funding and is working towards a system level preliminary design review later this year. The current concept (including integrated adaptive optics and instrumentation) will be reviewed with concentration on solutions to the unique engineering challenges for a four meter solar telescope that have been previously presented. The overall status will be given with a concentration on near term milestones and impact on final completion targeted in 2012.

The Advanced Technology Solar Telescope (ATST) is intended to be the premier facility for experimental solar physics. A premium has been placed on operating ATST as a laboratory-style observatory to maximize the flexibility available to solar physicists. In particular, the main observation platform is a rotating coude platform supporting eight optical benches on which instruments may be assembled from available components. The Virtual Instrument Model has been developed to formalize the operation of a facility where instruments may exist for a single experiment before components are reassembled into a new instrument. The model allows the laboratory-style operation to fit easily within a typical modern telescope control system. This paper presents one possible implementation of the Virtual Instrument Model that is based on the container/component model becoming increasing popular in software development.

The Advanced Technology Solar Telescope (ATST) is intended to be the premier solar observatory for experimental solar physics. The ATST telescope control software is designed to operate similar to current nighttime telescopes, but will contain added functionality required for solar observations. These additions include the use of solar coordinate systems, non-sidereal track rates, solar rotation models, alternate guide signal sources, the control of thermal loads on the telescope, unusual observation and calibration motions, and serendipitous acquisition of transient objects. These requirements have resulted in a design for the ATST telescope control system (TCS) that is flexible and well-adapted for solar physics experiments. This report discusses both the classical design of the ATST TCS and the modifications required to observe in a solar physics environment. The control and servo loops required to operate both the pointing and wavefront correction systems are explained.

The 4m Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope in the world, providing a unique scientific tool to study the Sun and possibly other astronomical objects, such as solar system planets. We briefly summarize the science drivers and observational requirements of ATST. The main focus of this paper is on the many technical challenges involved in designing a large aperture solar telescope. The ATST project has entered the design and development phase. Development of a 4-m solar telescope presents many technical challenges. Most existing high-resolution solar telescopes are designed as vacuum telescopes to avoid internal seeing caused by the solar heat load. The large aperture drives the ATST to an open-air design, similar to night-time telescope designs, and makes thermal control of optics and telescope structure a paramount consideration. A heat stop must reject most of the energy (13 kW) at prime focus without introducing internal seeing. To achieve diffraction-limited observations at visible and infrared wavelengths, ATST will have a high order (order 1000 DoF) adaptive optics system using solar granulation as the wavefront sensing target. Coronal observations require occulting in prime focus, a Lyot stop and contamination control of the primary. An initial set of instruments will be designed as integral part of the telescope. First telescope design and instrument concepts will be presented.

The National Solar Observatory's SOLIS project is building a new solar telescope to replace the existing Vacuum Telescope at Kitt Peak, Arizona. Three new solar instruments will replace existing capabilities and provide new scientific capabilities over the expected 25 year lifetime. The SOLIS instruments are the VSM (Vector SpectroMagnetograph), FDP (Full Disk Patrol), and ISS (Integrated Sunlight Spectrometer). Each provides a unique solar physics science capability for magnetic, image, and spectral data. Part of the challenge for the SOLIS software has been controlling and coordinating these varied instruments to work efficiently in a synoptic observing environment.

The BL Lacertae objects OJ 287 and BL Lac have been photometrically monitored in an effort to study the nature of optical variations which may occur on timescales ranging from years to less than a day. The results of ten years of photometric monitoring of these two objects show variations which are consistent with those reported by other authors. No strong dependence of color with source brightness was detected, although both sources exhibited a weak tendency to be bluer when brighter. Microvariability was observed for both objects; variations as large as 0.1 mag/hr were observed for BL Lac and changes as large as 0.08 mag/hr were observed for OJ 287. No evidence for a periodicity was found in the observed variations of either object.

Photometric and spectroscopic observations of Lanning 90 (V1776 Cyg) show that it is an eclipsing cataclysmic variable with an orbital period of 3h57m. The shape of the eclipse is variable, and the brightness out of eclipse can change by over a magnitude in less than a day. The broad-band light curves do not show a hump before eclipse, but time-resolved spectroscopy of one orbit suggests that the H-alpha emission-line strength peaks near phase 0.75. Observations of a number of orbits, however, are needed to confirm that the line strength depends on phase. The velocity amplitude of the primary is 144 + or - 20 km/s as measured from the wings of the H-alpha line. The masses of the components, the orbital inclination, and semimajor axis are estimated from the observations, but the derived system parameters are suspect since the spectroscopic phase lags the photometric phase by 70 deg. A similar shift has been observed in DW UMa and is attributed to a disturbance on the disk which contaminates the Balmer line wings. 20 refs.