Facility Instrument Distribution Optics (FIDO)
Description
The light distribution system on the coudé floor of DKIST plays a central role in how multiple instruments receive light simultaneously. FIDO consists of a suite of dichroic beamsplitters, windows and mirrors most of which are interchangeable so as to maintain the ability to feed instruments with a configurable variety of passbands in their design spectral ranges.
Concepts and Changeover Times
Enabling the full potential of DKIST requires the simultaneous use of multiple instruments that operate within their specific design spectral ranges. The spectral ranges of DKIST’s instruments often overlap: the scientific goal of an experiment often critically drives the need of a particular instrument’s unique capabilities within a given wavelength band.
FIDO feeds light to the instruments using an ensemble of interchangeable dichroic beamsplitters, windows and mirrors to facilitate many different optical configurations on the Coudé table. All positions in the FIDO path must have an optical element present.
The current list of FIDO is below.
Optic name | Optic type | Description |
|---|---|---|
C-M1 | Mirror | Used to reflect the incident light into a certain instrument optical path. |
C-W1 | Window | Used to pass the incident light into a certain instrument optical path. |
C-W2 | Window | Used to pass the incident light into a certain instrument optical path. |
C-BS465 | Dichroic Beamsplitter | Used to reflect the incident light within the wavelength band below ~470 nm into one optical path, while transmitting the incident light within the wavelength band above into another optical path. |
C-BS555 | Dichroic Beamsplitter | Used to reflect the incident light within the wavelength band below ~560 nm into one optical path, while transmitting the incident light within the wavelength band above into another optical path. |
C-BS643 | Dichroic Beamsplitter | Used to reflect the incident light within the wavelength band below ~635 nm into one optical path, while transmitting the incident light within the wavelength band above into another optical path. |
C-BS680 | Dichroic Beamsplitter | Used to reflect the incident light within the wavelength band below ~680 nm into one optical path, while transmitting the incident light within the wavelength band above into another optical path. |
C-BS950 | Dichroic Beamsplitter | Used to reflect the incident light within the wavelength band below ~965 nm into one optical path, while transmitting the incident light within the wavelength band above into another optical path. |
M9a | Mirror | Mirror that can be inserted into the beam quickly in order to direct the light beam into the Cryo-NIRSP, disabling the adaptive optics and all post adaptive optics instrumentation. |
Changing from one optical configuration to another is a manual process that requires up to one day to complete. DKIST operations seeks to minimize the changeovers within proposal cycles.
An exception is the light distribution to the Cryo-NIRSP, which is fed by a quickly removable mirror at the location M9a. The Cryo-NIRSP receives all the light and can currently not operate simultaneously with any of the other DKIST instrumentation or the adaptive optics system. Nevertheless, either configuration of M9a can be accessed within several tens of minutes. The first optical component at location CL1 is always the wavefront correction (WFC) beamsplitter which diverts 4% of the light to the adaptive optics system.
Publications
Harrington, D. M., Wöger, F., White, A. J., Sueoka, S. R., “Polarization modeling and predictions for DKIST, part 9: flux distribution with FIDO”, Journal of Astronomical Telescopes, Instruments, and Systems, 7, Issue 4, 048005 (2021)
Principal Investigator
Dr. David Harrington
National Solar Observatory
Beamsplitter configuration tool
DKIST Instruments