mountain profile Institute for Astronomy University of Hawaii


  HiVIS (High-resolution Visible and Infra-red Spectrograph) is two separate cross-dispersed echelle spectrographs using the 3.67m AEOS telescope on the 10,000ft Haleakala Mountain on Maui, Hawai'i. HVIS has both a visible (500-1000nm) spectrograph with a polarimetry package as well as a separate infra-red spectrograph (1.0-2.5 microns). The visible arm works at spectral resolutions of 12000 - 50000 while the infra-red arm is capable of 8000 - 33000 resolution.  The visible channel also has a low-resolution spectroscopy & spectropolarimetry mode (1000-3000) using only the cross-disperser.

Science:

  This spectrograph and spectropolarimeter is capable of unique measurements because of it's dual beam spectropolarimetry mode in both low and high spectral resolutions. It is a powerful spectrograph because of the wide wavelength coverage made possible by both optical and infra-red arms. This instrument is one of a handful of high-resolution spectropolarimeters available on large telescopes.

 

Spectropolarimeter:

  The visible spectrograph has two dual-beam polarimetry modes: rotating achromatic wave plates and fast-switching liquid crystals.  The achromats allow for precise coverage over a wide wavelength range while the liquid crystal mode allows for fast modulation with no moving optics. There are several science drivers for this spectropolarimeter in various areas of stellar and planetary astronomy enabled by the dual-beam and fast-switching capabilities.

 

Polarimetry:

HiVIS now has full-Stokes capability in both wave plate and liquid crystal modes.  Recent calibrations have shown that the AEOS telescope does not significantly induce polarization or depolarize. This means full-Stokes measurements are sufficient for both detections and non-detections.

 

 

science

Line Polarization:

Recent studies have discovered a wealth of linear polarization effects in obscured stars with complex morphologies and amplitudes greater than 1%. These polarization effects can be related to circumstellar material and used to constrain the near-star environment.

LoVIS:

Recently, a low-resolution mode has been implemented to utilize the dual-beam polarimeter using only the cross-disperser. This low-resolution mode allows higher time resolution as well as observations on fainter targets.

Charge-Shifting CCD:

New electronics have been installed on the original 4k by 4k array to enable bi-directional clocking of charge along the CCID20 columns. Charge is shuffled on microsecond timescales and can be synchronized with the liquid crystal retarders to enable a variety of observing modes for higher precision and sensitivity.

Charge-Shuffling:

Using the charge-shuffling capabilities of the new detector, multiple polarization states can be imaged on the same pixels on short time-scales to help minimize systematic errors such as telescope guiding drift and illumination changes as well as reducing overheads when observing bright targets by increasing the exposure time to saturation as well as reducing the number of readouts required.

Infra-Red Spectrograph:

The infrared spectrograph uses as its detector a Rockwell 2048 x 2048 pixel HAWAII-II array developed specifically for this project. The bulk of the optomechanics for the spectrograph were designed and built by IfA. The spectrograph was commissioned in early 2002. The instrument involved may including Jeff Kuhn, Klaus Hodapp, Gerry Luppino, Alan Stockton, and was the dissertation of former graduate student Bob Thornton. 

Infra-Red Spectrograph

The IR spectrograph has cross-dispersers to enable J, H and K band spectra at resolutions of up to 30,000 for use in a range of science programs.

Haleakala



  Haleakala is home to several world-class observatories and is a short 45 minute drive from the new Advanced Technology Research Center (ATRC) home of the Institute for Astronomy on Maui. There are the solar telescopes Mees and SolarC already in operation as well as the planned 4m ATST solar telescope. The night-time astronomical presence is very large and includes the 4m AEOS telescope, Pan-Starrs I and Faulkes 2m telescopes, the planned Pan-Starrs II and Planets telescopes, the coming 1m Harlington telescope as well as the many telescopes of the Maui Space Survailance Complex.

The observatory location is one of the best in the world. Located on a 3,000m (10,000ft) volcano surrounded by the Pacific Ocean, the air is particularly dry and stable. The inversion layer is typically at 1500-2000m, trapping low-level moisture well below the summit. The shield volcano has an average slope of 10-15 degrees leading to low turbulence. The isolation of the volcano leads to a dust-free atmosphere giving excellent atmospheric transparency..

Telescope

HiVIS utilizes the 3.67m AEOS telescope, currently the largest telescope in the DoD system.