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The ARC Echelle Spectrograph (ARCES) continues to be a popular and scientifically productive instrument among the users of the 3.5m telescope. Recent instrument usage statistics are below:

Year ARCES Usage (%)
2019 26.7
2018 33.9
2017 27.0
2016 27.0
2015 24.5

Now in its 21st year of operation on the 3.5m telescope, ARCES is starting to show its age; scattered (inter-order) light is becoming a significant issue during summer months, and the electronics are old and repairing/replacing them would be challenging. During the 3.5m Strategic Planning Meeting held in June 2019 a number of user representatives expressed the importance of retaining echelle capability on the 3.5m, thus in Spring 2020 an Echelle Advisory Group (EAG) was formed to begin exploring options for replacing ARCES.

The Telescope Engineering Group at the University of Washington is tasked with delivering KOSMOS to APO (Summer 2020?) and then designing/building a new fiber-fed optical spectrograph as an eventual replacement for DIS. Thus, the TEG will likely not have the bandwidth to also consider an echelle replacement within the next several years. The objective of the EAG is to collectively brainstorm other solutions for procuring a replacement for ARCES, e.g. identify other existing spectrographs with characteristics similar to those we wish to retain, which have already been designed (and/or built). In doing so, we may be able to pursue procuring a replacement echelle in parallel with other instrument development efforts undertaken by the UW TEG.

EAG Activities

The Echelle Advisory Group currently consists of the following members: * Nancy Chanover, NMSU, 3.5m Director * Ben Williams, UW, 3.5 Deputy Director * Sarah Tuttle, UW, 3.5m Instrument Scientist * Kal Kadlec, UW, 3.5m optical engineer * John Wisniewski, OU * Kevin Schlaufman, JHU * Derek Buzasi, FGCU * Yuta Notsu, CU * Kaike Pan, APO * Candace Gray, APO * Charli Sakari, UW → SFSU * Brett Morris, UW → University of Bern, Switzerland

Minutes from the meetings can be found here:

April 29, 2020


ARCES specifications:

Links to other optical spectrographs: * Gemini/GHOST * Keck/HIRES * Subaru/HDS

JHU white paper on a proposed echelle replacement:

SMARTS: Small and Medium Aperture Research Telescope System: (see info about the CHIRON high resolution spectrograph here: and here:

newechelle.txt · Last modified: 2022/03/11 16:43 by holtz