The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Research telescope since 2014. It was designed and built in collaboration between the University of North Carolina at Chapel Hill, and Cerro Tololo Inter-American Observatory. The device is installed in the elevation axis before the instruments mounted at the optical Nasmyth focus. It consists of two 300mm diameter sol-gel coated fused silica prisms, trombone mounted, which can be folded in or out of the beam. It is important for long slit spectroscopy, and essential for Multi-Object Slit spectroscopy. We present optical and mechanical designs, electronics and software control, and on-sky performance.
Hector is an instrument concept for a multi integral-field-unit spectrograph aimed at obtaining a tenfold increase in
capability over the current generation of such instruments. The key science questions for this instrument include how do
galaxies get their gas, how is star formation and nuclear activity affected by environment, what is the role of feedback,
and what processes can be linked to galaxy groups and clusters. The baseline design for Hector incorporates multiple
hexabundle fibre integral-field-units that are each positioned using Starbug robots across a three-degree field at the
Anglo-Australian Telescope. The Hector fibres feed dedicated fixed-format spectrographs, for which the parameter space
is currently being explored.
We demonstrate for the first time an imaging fibre bundle ("hexabundle") that is suitable for low-light applications in
astronomy. The most successful survey instruments at optical-infrared wavelengths today have obtained data on up to a
million celestial sources using hundreds of multimode fibres at a time fed to multiple spectrographs. But a large fraction
of these sources are spatially extended on the celestial sphere such that a hexabundle would be able to provide
spectroscopic information at many distinct locations across the source. Our goal is to upgrade single-fibre survey
instruments with multimode hexabundles in place of the multimode fibres. We discuss two varieties of hexabundles: (i)
closely packed circular cores allowing the covering fraction to approach the theoretical maximum of 91%; (ii) fused noncircular
cores where the interstitial holes have been removed and the covering fraction approaches 100%. In both cases,
we find that the cladding can be reduced to ~2μm over the short fuse length, well below the conventional ~10λ thickness
employed more generally. We discuss the relative merits of fused/unfused hexabundles in terms of manufacture and
deployment, and present our first on-sky observations.
Travel from North America to the 4.1m SOAR telescope atop Cerro Pachon exceeds $1000, and takes >16 hours door to door (20+ hours typically). SOAR aims to exploit best seeing, requiring dynamic scheduling that is impossible to accomplish when catering to peripatetic astronomers. According to technical arguments at www.peakoil.org, we are near the peak rate of depleting world petroleum, so can expect travel costs to climb sharply. With the telecom bubble's glut of optical fiber, we can transmit data more efficiently than astronomers and "observe remotely". With data compression, less than half of the 6 Mbps bandwidth shared currently by SOAR and CTIO is enough to enable a high-fidelity observing presence for SOAR partners in North America, Brazil, and Chile. We discuss access from home by cable modem/DSL link.
The SOAR telescope will begin science operations in 3Q 2003. From the outset, astronomers at all U.S. research universities will be able to use it remotely, avoiding 24+ hrs of travel, and allowing half-nights to be scheduled to enhance scientific return. Most SOAR telescope systems, detector array controllers, and instruments will operate under LabVIEW control. LabVIEW enables efficient intercommunication between modules executing on dispersed computers, and is operating-system independent. We have developed LabVIEW modules for remote observing that minimize bandwidth to the shared LAN atop Cerro Pachon. These include control of a Polycom videoconferencing unit, export of instrument control GUI's and telescope telemetry to tactical displays, and a browser that first compresses an image in Chile by a factor of 256:1 from FITS to JPEG2000 and then sends it to the remote astronomer. Wherever the user settles the cursor, a region-of-interest window of lossless compressed data is downloaded for full fidelity. As an example of a dedicated facility, we show layout and hardware costs of the Remote Observing Center at UNC, where instruments on SOAR, SALT, and other telescopes available to UNC-CH astronomers will be operated.
Five SOAR instruments are being designed for high-resolution imaging/imaging spectrophotometry across the isokinetic field and queued/remote observing. Wavefront tilt will be sensed in instruments and corrected by jittering M3. SDSU-2 'Leach' controllers under LabVIEW will operate most detector arrays. All optical instruments emphasize high UV throughput, and will use pairs of UV-enhanced MIT/LL 2 by 4 K CCDs. The University of Sao Paulo may provide a 1500- element integral field lenslet array that is fiber-coupled to a compact spectrography. VPH gratings will be used in this instrument and in the multi-slit spectrometer from the University of North Carolina at Chapel Hill. CTIO will provide an optical mosaic imager with 'trombone'-style ADC, and may also upgrade their IRS with its large complement of existing gratings to a 1 by 1K Hawaii array. Michigan State University may build a 4 by 4K near-IR imager with tunable Lyot filter. Most instruments will be clustered at Nasmyth ports where payload totals 4400 kg. Facility units will allow calibration while another instrument is doing science. The baseline for mechanism control is LabVIEW under Linux in a Compact PCI chassis that is fiber-linked by MXI-3 to a dedicated PC.
The optical design and performance of the visible/NIR imaging Fabry-Perot interferometers for the 3.6-m CFHT, the 2.2-m University of Hawaii Telescope, and the 3.9-m UKIRT (all at Mauna Kea) are described. The basic configuration combines a high-finesse etalon of free spectral range about 10 nm with a state-of-the-art CCD image-plane array. The criteria considered in selecting the CCDs and etalons are discussed; the quality of the data obtainable is illustrated with sample data (CFHT 658.3-nm emission line profiles of the central region of NGC 1068 and UKIRT B-gamma profiles of the Galactic center); and the instrument calibration and artefact problems are outlined. It is suggested that, while Fabry-Perot devices offer the best visible-NIR performance at present, Fourier-transform and long-slit spectroscopy show great promise for the future, especially in the IR.