We report on the implementation of a star tracker camera to improve the telescope pointing and tracking, at the
WIYN 3.5 m telescope on Kitt Peak, Arizona. We base the overall concept on a star tracker system developed
at the University of Wisconsin and routinely in use now for rocket and high-altitude balloon navigation. This
fairly simple system provides pointing and station-keeping information, accurate to a few arcseconds, typically
within a second.
The One Degree Imager (ODI) was deployed during the summer of 2012 at the WIYN 3.5m telescope, located on Kitt Peak near Tucson, AZ (USA). ODI is an optical imager designed to deliver atmosphere-limited image quality (≤ 0.4” FWHM) over a one degree field of view, and uses Orthogonal Transfer Array (OTA) detectors to also allow for on-chip tip/tilt image motion compensation. At this time, the focal plane is partially populated (”pODI”) with 13 out of 64 OTA detectors, providing a central scientifically usable field of view of about 24′ x 24′; four of the thirteen detectors are installed at outlying positions to probe image quality at all field angles. The image quality has been verified to be indeed better than 0.4′′ FWHM over the full field when atmospheric conditions allow. Based on over one year of operations, we summarize pODIs performance and lessons learned. As pODI has proven the viability of the ODI instrument, the WIYN consortium is engaging in an upgrade project to add 12 more detectors to the focal plane enlarging the scientifically usable field of view to about 40′ x 40′. A design change in the new detectors has successfully addressed a low light level charge transfer inefficiency.
The WIYN One Degree Imager (ODI) will provide a one degree field of view for the WIYN 3.5 m telescope located on
Kitt Peak near Tucson, Arizona. Its focal plane consists of an 8x8 grid of Orthogonal Transfer Array (OTA) CCD
detectors. These detectors are the STA2200 OTA CCDs designed and fabricated by Semiconductor Technology
Associates, Inc. and backside processed at the University of Arizona Imaging Technology Laboratory. Several lot runs
of the STA2200 detectors have been fabricated. We have backside processed devices from these different lots and
provide detector performance characterization, including noise, CTE, cosmetics, quantum efficiency, and some
orthogonal transfer characteristics. We discuss the performance differences for the devices with different silicon
thickness and resistivity. A fully buttable custom detector package has been developed for this project which allows
hybridization of the silicon detectors directly onto an aluminum nitride substrate with an embedded pin grid array. This
package is mounted on a silicon-aluminum alloy which provides a flat imaging surface of less than 20 microns peakvalley
at the -100 C operating temperature. Characterization of the package performance, including low temperature
profilometry, is described in this paper.
SALT uses the Principal Investigator Proposal Tool (PIPT) for generating, checking, submitting and editing
proposals. The PIPT maps XML into Java classes with immediate error and consistency checking, and thus
prevents non-feasible observation requests. Various tools allow the user to simulate SALT observations. These
include standard source spectra (e.g. black body, power law, Kurucz model atmospheres), and allow users to
add their own library spectra. The PIPT is complemented by the Web Manager for administering submitted
proposals. It is discussed how the code of these tools can easily be extended for future instruments and used for
QUOTA is an 8Kx8K (16'x16') optical imager using four 4Kx4K orthogonal transfer CCDs arrays (OTAs). Each OTA
has 64 nearly independent CCDs having 480x494 12μm pixels. By reading out several of the CCDs rapidly (20 Hz), the
centroids of the stars in those CCDs can be used to measure image motion due to atmospheric effects, telescope shake,
and guide errors. Motions are fed back to the remaining 250 CCDs that continue to integrate normally, allowing a shift
of the collecting charge packets so that they always fall under the moving star images, thereby effecting low order
adaptive optics tip/tilt correction in the silicon to improve image quality. As a bonus, the stars that are read rapidly can
be studied for high speed photometric variability.
QUOTA was conceived to be a prototype for WIYN's 32Kx32K One Degree Imager (ODI), providing a means to test
and advance the technical developments for the larger imager (e.g., detectors, controllers, optics, coatings, cooling, and
software). QUOTA will have been to the WIYN 3.5-m telescope only twice in its current configuration, but it provided
a wealth of information that has been useful to the engineering of ODI. We focus on the areas in which ODI has
benefited from QUOTA in this report.
The WIYN One Degree Imager (ODI) exposure system must drive multiple complex subsystems requiring large
amounts of configuration information that may change substantially between exposures. The mosaic OTA focal plane
provides up to 64 streams of image data during readout or 512 ROI video streams for guidance or real time photometry.
The work flows and instrument operation sequences are numerous, and are evolving to adapt to the new capabilities the
mosaic OTA (Orthogonal Transfer Array) camera presents. By making scripting data driven, the ODI exposure system
provides a very flexible, but structured and powerful paradigm for instrumentation process control and operation.
User interfaces (UIs) are a necessity for almost any data acquisition system. The development team for the WIYN One
Degree Imager (ODI) chose to develop a user interface that allows access to most of the instrument control for both
scientists and engineers through the World Wide Web, because of the web's ease of use and accessibility around the
world. Having a web based UI allows ODI to grow from a visitor-mode instrument to a queue-managed instrument and
also facilitate remote servicing and troubleshooting. The challenges of developing such a system involve the difficulties
of browser inter-operability, speed, presentation, and the choices involved with integrating browser and server
technologies. To this end, the team has chosen a combination of Java, JBOSS, AJAX technologies, XML data
descriptions, Oracle XML databases, and an emerging technology called the Google Web Toolkit (GWT) that compiles
code in Java, GWT's native support for AJAX, the use of XML to describe the user interface, the ability to profile code
speed and discover bottlenecks, the ability to efficiently communicate with application servers such as JBOSS, and the
ability to optimize and test code for multiple browsers. We discuss the inter-operation of all of these technologies to
create fast, flexible, and robust user interfaces that are scalable, manageable, separable, and as much as possible allow
maintenance of all code in Java.
The One Degree Imager will be the future flagship instrument at the WIYN 3.5m observatory, once commissioned in
2011. With a 1 Gigapixel focal plane of Orthogonal Transfer Array CCD devices, ODI will be the most advanced optical
imager with open community access in the Northern Hemisphere. In this talk we will summarize the progress since the
last presentation of ODI at the SPIE 2008 meeting, focusing on optics procurement, instrument assembly and testing, and
As camera focal planes become larger, with higher resolutions and increasingly higher data throughputs, the more they
resemble the enterprise data systems found in commercial data centers. The WIYN One Degree Imager (ODI) is such a
system. ODI is a mosaic imager with 64 independent CCD detectors with a total resolution of approximately a gigapixel,
covering 1 square degree of the sky at the WIYN 3.5 m telescope at Kitt Peak. The ODI camera will bring improved
seeing, widefield imaging, new modes of operation and automated integration with the NOAO Science Archive. It will
also become the workhorse instrument of the observatory, with high availability and reliability. The new flexibility of
the camera will allow (and require) constant refinement of imaging techniques, and calibration and maintenance
Large scale, parallel data processing, management and control will be a constant in the operation of the instrument. We
are developing an enterprise level data system using typical Java J2EE constructs. With the advent of relatively
inexpensive clustered hardware, scaling of image operations and management to the large volumes of data in ODI
should be simplified. We describe an architecture in construction for ODI's 2010 deployment.
The WIYN Consortium is building the One Degree Imager (ODI) for its 3.5m telescope, located at Kitt Peak, Arizona
(USA). ODI will utilize both the excellent image quality and the one degree field of view of the WIYN telescope. Image
quality will be actively improved by localised tip/tilt image motion stabilisation using a novel concept of Orthogonal
Transfer Array (OTA) CCDs, which are a new detector type jointly developed with the PanSTARRS project. Its anticipated
median image quality of ≤ 0.55" in the R band will make ODI a unique and competitive instrument in the landscape of the
next generation of large field imagers.
A conceptual design of ODI was presented earlier at SPIE.1 In the meantime, this concept matured, the ODI project has
been fully funded, and it has entered the construction phase. A prototype camera (QUOTA) with a field of view of 16'x16'
has already seen first star light in fall 2006. In this paper we report on the evolution of ODI's definition, the design of its
components, the status of the OTA detector development, and the path towards first light in early 2010. In accompanying
papers we detail the design of the ODI's optical corrector, the mechanical structures, and the software & instrument system
The main advantage of the WIYN One Degree Imager (ODI) over other wide-field imagers will be its exceptional image quality. The fine pixel scale (0.11") provides uncompromised sampling of stellar PSFs under most conditions (seeing >0.3"). The telescope routinely delivers the site seeing (median ~ 0.7") which is often below 0.5" FWHM, and can be as low as 0.25". The ODI specifications require the optics to maintain native high quality images. A two-element, fused silica, corrector meets the geometric error budget of 0.10" images, but the first element requires a mildly aspheric surface. The other element serves as the dewar window. A pair of cemented prisms (fused silica plus PBL6Y) serve as an ADC, which is essential to meet the image quality requirements for many observing programs. We describe the optical design details and its performance, the tolerances required, and the trade-offs considered for anti-reflection coatings. This paper is an update to a preliminary three-element design.
The WIYN consortium is building the One Degree Imager (ODI) to be mounted to a Nasmyth port of the WIYN 3.5m
telescope, located at Kitt Peak, Arizona (USA). ODI will utilize both the excellent image quality and the one-degree
field of view that the telescope delivers. To accommodate the large field of view (~0.39m diameter unvignetted field
with 0.54m across the diagonal of the one-degree-square, partially vignetted field), 0.6m-class optics are required. The
ODI design consists of a two element corrector: one serves as a vacuum barrier to the cryostat, the other is an asphere;
two independently rotating bonded prism pairs for atmospheric dispersion compensation (ADC); nine independently
deployable filters via a simple pivoting motion; and a 971 mega-pixel focal plane consisting of 64 orthogonal transfer
array (OTA) devices.
This paper is an overview of the mechanical design of ODI and describes the optical element mounting and alignment
strategy, the ADC & filter mechanisms, plus the focal plane. Additionally, the project status will be discussed.
In accompanying papers Jacoby1 describes ODI's optical design, Yeatts2 describes the software and control system
design, and Harbeck3 gives a general update on the project.
We describe a plan to study the radial velocity of low mass stars and brown dwarfs using a combination of interferometry and multichannel dispersive spectroscopy, Externally Dispersed Interferometry (EDI). The EDI technology allows implementation of precision velocimetry and spectroscopy on existing moderate-resolution echelle or linear grating spectrograph over their full and simultaneous bandwidth. We intend to add EDI to the new Cornell TripleSpec infrared simultaneous JHK-band spectrograph at the Palomar Observatory 200" telescope for a science-demonstration program that will allow a unique Doppler-search for planets orbiting low mass faint M, L and T type stars. The throughput advantage of EDI with a moderate resolution spectrograph is critical to achieving the requisite sensitivity for the low luminosity late L and T dwarfs.