André-Nicolas Chené
GRACES:
The Beginning of a Scientific Legacy
The Gemini/Canada-France-Hawai‘i (CFHT) partnership to provide
Gemini users with access to the CFHT’s high-resolution optical
spectrograph ESPaDOnS is now complete. Called GRACES, initial
commissioning in 2015 was a resounding success, and regular
operations have already started in Semester 2015B. This project
provides users with a powerful new capability of high-resolution
optical spectroscopy.
The Gemini Remote Access to CFHT’s ESPaDOnS Spectrograph (GRACES) project has had a
long and interesting history. Suffice it to say, however, that there has always been a healthy
level of skepticism about the feasibility of the project and the likelihood of its success.
History and Background on GRACES
At the core of early doubts was the project’s need for two 270-meter-long fiber cables (Figure 1) to feed light from the 8-meter primary of Gemini North into ESPaDOnS — a benchmounted high-resolution échelle spectrograph and spectropolarimeter at CFHT designed
to obtain a complete optical spectrum — from 370 to 1050 nanometers (nm) — in a single
exposure (see Figure 2). Could light travel through such a fiber and make it to the other
end without a lot of it being lost in the process? This was the key question and risk in the
project. GRACES can now answer this question affirmatively, having achieved success earlier this year, thereby marking a major milestone for astronomy. The result allows Gemini to
share the ESPaDonS instrument with CFHT and provide a short and inexpensive way to add
a significant new user-desired capability in the process.
Key to the GRACES success was the challenging job completed by the National Research
Council-Herzberg (Canada) to create the GRACES fiber cable (the longest astronomical fiber ever made) in collaboration with FiberTech Optica. Together they worked more than a
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