UW astronomers build unique astronomical instruments to investigate properties of the light coming from stars and gas in the Milky Way and in external galaxies near and far.
We have a long history of building innovative instruments to make measurements of celestial objects. In the 20th century, UW astronomers pioneered ground-breaking work in photoelectric photometry, ultraviolet research from suborbital sounding rockets and observatories in space, and very high time-resolution photometry.
Some of the outstanding achievements of this program that remain current and under active development include telescope control-systems and remote observing (WIYN), data compression for low-bandwidth transmission of images from space (PIT), and control systems for yaw-pitch-roll and autonomous attitude determination of sub-orbital rockets and high-altitude balloons, e.g., the mighty Star Tracker 5000.
Today, our program specializes in building two-dimensional spectroscopic instruments capable of detecting signals at ultra-low light levels from the UV to the infrared, and projecting our legacy of spectro-polarimetry and high time-resolution spectroscopy.
The instruments we build achieve high spectral-resolution and large wavelength coverage for both multi-object and extended, diffuse-source study. To reach these goals we exploit our expertise in interferometric techniques (Fabry-Perot and spatial-heterodyne spectroscopy) as well as integral-field spectroscopy with fiber-optics and image-slicers. Some current instrument efforts include:
- The Robert Stobie Spectrograph (RSS) on the 11m South African Large Telescope (SALT): RSS covers a very wide spectral range from the near-UV atmospheric cutoff (320 nm) out to 1700 nm in the near-infrared (NIR). This very wide coverage allows simultaneous visible and NIR observations, possible by having two independently configurable cameras and dispersors sampling the same part of the sky. The visible beam is already on the telescope, collecting forefront data. The near-infrared beam is under construction here in Madison. Fabry-Perot etalons and a suite of volume-phas holographic gratings enable panoramic spectroscopy covering an 8 arcminute field of view over a wide range of spectral resolutions.
- The Wisconsin H-alpha Mapper (WHAM): This dedicated astronomical instrument contains a Fabry-Perot interferometer application unique to astronomy. WHAM is used in a non non-imaging mode to survey the ionized gas in the Milky Way, 1 degree at a time, at a spectral resolution of nearly 10 km/s. WHAM was first located at Kitt Peak, and now resides at Cerra Telolo to map the southern sky.
- The WIYN Bench Spectrograph and its fiber-optic feeds: This spectrograph facility instrument is the work-horse of the WIYN 3.5m telescope. The spectrograph is fed by a multi-object fiber-optic feed patrolling a 1 degree field of view, and a fiber intergral-field unit (IFU), called SparsePak, built at Wisconsin. Two more IFUs, HexPak and GradPak, are under construction here. We recently redesigned and upgraded the spectrograph optics, detector and gratings, thereby more than doubling its throughput.
- The Star Tracker 5000: this is a low-cost, rugged device that calculates where it is pointing based on analyzing patterns of faint stars. It can determine its inertial attitude in a few seconds, and can track changes in its pointing, 10 times per second, with an accuracy of about an arc-second (1/3600 of a degree). It is currently used in all NASA’s sub-orbital rockets for astrophysics, and has flown on over 40 missions. It has enabled new kinds of science on these rocket missions, with fast, reliable attitude determination and ability to operate in faint fields without bright guide stars.