The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of 156 identical spectrographs fed by 35,000 fibers from the upgraded 10-meter Hobby-Eberly Telescope (HET). VIRUS is in a phased deployment. At the submission of this paper, over half of the units are installed and the full support infrastructure is operational. This paper will describe the VIRUS infrastructure which includes the physical support system, the air cooling, the cryogenic cooling, and the temperature control of VIRUS. The paper will also discuss the various installation, maintenance, and operational procedures based on growing experience with the VIRUS array.
The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of 156 identical spectrographs (arrayed as 78 pairs, each with a pair of spectrographs) fed by 35,000 fibers, each 1.5 arcsec diameter, at the focus of the upgraded 10 m Hobby-Eberly Telescope (HET). VIRUS has a fixed bandpass of 350-550 nm and resolving power R~750. The fibers are grouped into 78 integral field units, each with 448 fibers and 20 m average length. VIRUS is the first example of large-scale replication applied to optical astronomy and is capable of surveying large areas of sky, spectrally. The VIRUS concept offers significant savings of engineering effort and cost when compared to traditional instruments. The main motivator for VIRUS is to map the evolution of dark energy for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), using 0.8M Lyman-alpha emitting galaxies as tracers. The VIRUS array has been undergoing staged deployment starting in late 2015. Currently, more than half of the array has been populated and the HETDEX survey started in 2017 December. It will provide a powerful new facility instrument for the HET, well suited to the survey niche of the telescope, and will open up large spectroscopic surveys of the emission line universe for the first time. We will review the current state of production, lessons learned in sustaining volume production, characterization, deployment, and commissioning of this massive instrument.
The Hobby-Eberly Telescope is an innovative 10-meter telescope, located at the McDonald Observatory. We have completed a major multi-year upgrade of the HET that has substantially increased the field of view to 22 arcminutes by replacing the optical corrector, tracker, and prime focus instrument package and by developing a new telescope control and metrology systems. The metrology systems include four independent optical sensors to provide fully redundant alignment and pointing information to keep the telescope aligned to within a few microns and a few arc seconds. We detail the design, implementation, on-sky performance, and lessons learned.
The Hobby-Eberly Telescope (HET) is an innovative large telescope with 10 meter aperture, located in West Texas at the McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker, which moves the fourmirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. We have completed a major multi-year upgrade of the HET that has substantially increased the field of view to 22 arcminutes by replacing the optical corrector, tracker, and prime focus instrument package and by developing a new telescope control system. The upgrade has replaced all hardware and systems except for the structure, enclosure, and primary mirror. The new, reinvented wide-field HET feeds the revolutionary Visible Integral-field Replicable Unit Spectrograph (VIRUS‡), fed by 35,000 fibers, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX§), a new low resolution spectrograph (LRS2), the Habitable Zone Planet Finder (HPF), and the upgraded high resolution spectrograph (HRS2). The HET Wide Field Upgrade has now been commissioned and has been in science operations since mid 2016 and in full science operations from mid 2018. This paper reviews and summarizes the upgrade, lessons learned, and the operational performance of the new HET.
The Hobby-Eberly Telescope (HET) is an innovative large telescope, located in West Texas at the McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker, which moves the four-mirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. We have completed a major multi-year upgrade of the HET that has substantially increased the pupil size to 10 meters and the field of view to 22 arcminutes by replacing the corrector, tracker, and prime focus instrument package. The new wide field HET will feed the revolutionary integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX§), a new low resolution spectrograph (LRS2), an upgraded high resolution spectrograph (HRS2), and later the Habitable Zone Planet Finder (HPF). The upgrade is being commissioned and this paper discusses the completion of the installation, the commissioning process and the performance of the new HET.
The Hobby-Eberly Telescope (HET) is an innovative large telescope located in West Texas at the McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker, which moves the four-mirror optical corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. A major upgrade of the HET is in progress that will substantially increase the pupil size to 10 meters (from 9.2 m) and the field of view to 22 arcminutes (from 4 arcminutes) by replacing the corrector, tracker, and prime focus instrument package. In addition to supporting existing instruments, and a new low resolution spectrograph, this wide field upgrade will feed a revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX§). The upgrade is being installed and this paper discusses the current status.
The HET is a modified Arecibo-style telescope with a segmented spherical primary and a four-mirror spherical
aberration corrector (SAC). Objects are tracked by driving the SAC along the focal sphere of the primary. In the original
design of the telescope the alignment of the SAC was to be maintained passively. In practice, this could not be done to
specifications, leading to degraded imaging quality. We have developed a metrology system to actively control the
alignment of the SAC. An autocollimator maintains the optical axis of the SAC normal to the primary mirror beneath it.
An absolute distance measuring interferometer (DMI) monitors the SAC/primary mirror distance, maintaining focus.
Both systems work at a wavelength of 1.5 microns, well above the operating wavelength of current or planned science
instruments and therefore do not interfere with observations. The performance of the system is measured via Hartmann
testing.
Several upgrades are implemented in the primary mirror control system, including calibration of individual edge
sensors, new control system software, and a new method of setting and controlling the overall radius of curvature of the
primary array. New techniques were developed to efficiently piston the segments onto the proper sphere radius.
KEYWORDS: Sensors, Mirrors, Space telescopes, Telescopes, Control systems, Calibration, Sensor calibration, Temperature metrology, Image quality, Process control
The Segment Alignment Maintenance System (SAMS) is a control system to maintain the alignment of the 91 segment Hobby-Eberly Telescope (HET) primary mirror array. The system was developed by Blue-Line Engineering (Colorado Springs, CO) and NASA-Marshall Space Flight Center (Huntsville-Al). The core of the system is a set of 480 inductive edge sensors which measure relative shear between adjacent segments. The relative shear is used to calculate segment tip/tilt and piston corrections. Although the system has dramatically improved the performance of the HET it does not meet its error budget due to thermal drifts in the sensors. The system is now sufficiently stable that it routinely requires only one primary mirror alignment at the beginning of the night. We describe methods to calibrate this sensor drift.
This paper describes recent developments in three areas ofmasked ion beam lithography (MIBL). These are 1) fabrication
oflarge area, low distortion, silicon stencilmasks for demagnifying ion projection lithography, 2) fabrication ofstencil masks
with nanometer scale resolution for 1:1 proximity printing, and 3) development of a direct method of alignment using the
ion beam induced fluorescence of Si02. These topics are discussed below.
Demagnifying ion projection masks: We describe the fabrication of stencil masks in large area, low stress (10 MPa), n-type
silicon membranes. The projection masks have a silicon foil area 95 mm in diameter, thicknesses between 1.5-5 and
resolution of0.6um. Measured distortion (3a) in the IPL masks ranges between 0.23gm and 0.65,um, with an experimental
error of 0.20 1um.
Proximity printing masks: A process is described for fabricating stencil masks with 50 nm resolution in low stress, n-type
silicon membranes. Membranes less than 0.5 ,ttm thick are shown to be free of the sidewall taper that limits resolution in
thicker masks. These thin membranes show a slightly flared profile due to the imperfectly collimated etching ions.
Alignment: A direct method of alignment is being developed which uses the ion beam induced fluorescence of Si02 marks.
Fluorescence yield is characterized as a function of ion energy and resist coating thickness. The yield for Si02 is in the range
between 0.1-1.0 photons/proton, while the yields for Si, Al, and photoresist are negligibly small. Thus, a simple alignment
technique can be implemented where registration of a grating in the mask with a corresponding oxide pattern is detected
as a fluorescence maximum. A simple model predicts that 50 nm alignment can be accomplished, following a 1 im
prealignment, in 2 seconds.
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.