First 4-Telescope Fringes at the CHARA Array

CHARA Array Website
First Fringes with MIRC | First Closure Phase at CHARA Array | First 4-Telescope Fringes

From John Monnier, University of Michigan
18 September 2005.

Following our successful first fringes and first closure phases, the MIRC Commissioning Team has achieved our final major technical goal of this run (which ends tomorrow):

Simultaneous 4-telescope fringes!

With 4 telescopes, the MIRC combiner produces 6 fringe visibilities, 4 closure phases, and 3 closure amplitudes simultaneously. This is the first time that an optical/infrared interferometer has produced closure amplitudes. The star(s) was Iota Peg and the time was 11:19pm local time on UT 2005Sep18.

Unfortunately, the seeing was horrible (r0 ~3cm) and clouds shut us down after only 1/2 hour of fringes. Hopefully tomorrow night we can collect calibrated data.

I've attached a few photos and images.

Screenshot of Gui showing the 6 simultaneous fringes as 12 symmetric peaks in the power spectrum (red plot on right).
Picture of John Monnier toasting the core team, Nathalie Thureau and Ettore Pedretti (Ming Zhao taking the picture).
PDF file showing some crudely analyzed data. One can see an example snapshot of fringes at the top (dominated by a medium-frequency fringe). The bottom contains the fringe power spectra as a function of wavelength channel. The signal-to-noise is not very high, but all 6 fringes are clearly visible in the average power spectrum. All this data is in the H-band (1.5-1.8 microns).
This image shows the heart of the MIRC combiner, the silicon v-groove and lenslet array. In MIRC, we inject CHARA light into single-mode fibers and rearrange them to form a non-redundant linear array, allowing multiplexing of all available baselines via an image plane combiner with low-resolution spectroscopic capabilities.

I guarantee this is my last communication for this commissioning run. I will not repeat all my thanks here -- please see my last two emails describing first fringes and closure phases. Its been a great run.

Also see John Monnier's Homepage

Funding for the CHARA Array has been provided by the National Science Foundation, the W. M. Keck Foundation, the David and Lucile Packard Foundation, and Georgia State University.

Funding for Michigan Infrared Combiner has been provided by the University of Michigan and the National Science Foundation.

Maintained by Peter Lawson
MS 301-451, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109

Webmaster: Peter R. Lawson