Ejercito, Kiana intern photo 2023

Kiana Ejercito is from the island of Oahu.  She graduated from Kalani High School and currently attends the University of Hawaii at Manoa, pursuing a Bachelor of Science in Astrophysics.  Kiana is passionate about outreach and volunteers for events such as the Science Olympiad and events run by the Institute for Astronomy.  In the future, she hopes to continue research and inspire others to become interested in science. In her free time, she enjoys reading and listening to music.

Home Island: Oahu

High School: Kalani High School

Institution when accepted: University of Hawaii at Manoa

Fiber-Optic Performance Requirements for Keck’s FOBOS Instrument

Project Site: University of California Observatories, Santa Cruz, CA

Mentor: Kyle Westfall

Project Abstract:

The Fiber-Optic Broadband Optical Spectrograph (FOBOS) is a novel spectrograph in development for the Keck II Telescope at the W. M. Keck Observatory on Maunakea.  FOBOS will deploy thousands of optical fibers to convey light collected at the telescope focal plane to a set of spectrographs.  Currently, most astronomical instruments use fibers with a numerical aperture (NA) of 0.22 that outputs a fast beam, requiring the optical system to be larger and more expensive to capture the output light.  FOBOS thus aims to use fibers with a smaller NA to produce a slower beam, reducing the cost of the spectrographs.  However, low-NA fibers are expected to be more susceptible to throughput losses.  In this project, we use a test bench to determine performance requirements needed for potential integration into the FOBOS design.  First, we test our optical setup by measuring output focal ratio, throughput, and focal-ratio degradation (FRD) to measure the performance of standard fibers.  These tests were performed using fibers similar to those used by the Dark Energy Spectroscopic Instrument (DESI), which are multi-mode mode fibers with 107-?m cores and NA = 0.22.  Second, we analyze the output focal ratio, throughput, and FRD of fibers with 200-?m cores and NA = 0.12, then compare the throughput when stress is applied to determine throughput loss.  This comparison allows us to determine whether using fibers with a smaller NA will be feasible for FOBOS.  Future work will focus on measuring fiber-to-fiber performance variations to develop acceptance testing protocols to meet FOBOS’s strict calibration requirements.