Version 1 (modified by trac, 6 months ago) ( diff )


Minutes from Echelle Advisory Group Zoom Meeting on Wednesday April 29, 2020, 10:00-11:00 MDT

Attendees: Nancy Chanover (in and out due to poor internet connectivity - SORRY!), Ben Williams, Sarah Tuttle, Kal Kadlec, John Wisniewski, Kevin Schlaufman, Derek Buzasi, Yuta Notsu, Candace Gray, Charli Sakari, Brett Morris


  • review of ARCES capabilities that
    • we must retain
    • would be nice to retain
  • discussion of capabilities that ARCES currently does NOT offer that we would like to have
  • brainstorming different [existing] options of instruments that we could consider duplicating, with or without much modification

Notes from Discussion:

We started with the question of whether the echelle could be elevated in terms of priority for instrument replacements at APO. Given that there is already a mature design for Ocotillo (the new DIS replacement) and a fair amount of time/money invested, we will continue to move forward with that effort. However, Nancy would like to pursue echelle opportunities in parallel with Ocotillo development, so indeed the echelle replacement is being given a high priority. Sarah recommended that we should take a slightly different approach when defining the requirements for a replacement echelle than what the New Spectrograph Committee did when exploring DIS replacement options. Rather than providing a comprehensive list of options with varying degrees of feasibility for our site and telescope, which left the instrument designers to sort through and assess those trades, we should develop a cooperative vision of a new echelle spectrograph that will best suit our users (recognizing and accepting the fact that there will be trades).

General discussion about ARCES capabilities we would like to retain led to the assertion that we want to continue to have the broad wavelength coverage all in one shot. Comparable spectral resolution is also a must.

Kevin described an ambitious instrument that JHU is pursuing (see white paper in Resources section of this wiki). The new capability it would provide is precision RV, which would enable 3.5m users to expand into the research areas of exoplanet atmospheres and eclipsing binaries. The instrument is an existing design that NASA funded in the competition that led to the selection of NEID. The MIT instrument (Gabor Furesz's instrument) was the one not selected; however, given that it was designed for WIYN, which is a near clone to the ARC 3.5m, it would be a logical fit for APO. Kevin and some JHU colleagues proposed this instrument concept to an internal JHU competition to send this idea to the Sloan Foundation. Their big idea, which would be facilitated by this instrument, is finding habitable Earths. When asked how this would be different from the Terra Hunting Experiment (which will be looking at ~ 40 stars every night for the next 5-10 years), the answer is that this proposed instrument would be capable of that but would do Doppler followup for objects that could then be observed with JWST. Getting accurate masses gives the scale height of the atmospheres, which would be used to determine what is worth following up with JWST. So this proposed initiative would be about finding Earths and characterizing their atmospheres. It's not quite a cross between THE and HARPS-North because HN only goes out to 700 nm; this would go to longer wavelengths. There was some discussion of whether an iodine cell could be included; Kevin responded that in order for that to be effective we would also need higher spectral resolution (like PFS on Magellan). The ballpark budget for this ambitious instrument is $9M.

On the more inexpensive end, we discussed more off-the-shelf type of options (e.g. a Shelyak). Both Derek and Charli have experience with these instruments. They are not easy to use because they are intended to be a black box. The hardware of ARCES is not orders of magnitude better than a Shelyak, but the fact that everything is integrated into TUI (including the guider) is a tremendous benefit. The Shelyak comes with something for guiding but it is not clear how to implement it in remote operations.

Yuta mentioned that for his science, a baseline requirement for a new instrument is better time resolution. The ARCES readout time is ~ 3 min, and for flare science that’s too long.

Sarah mentioned that in her conversations with Shri Kulkarni (CalTech) he could not rally enough support for designing/building a new echelle, and instead they are going with a low res optical spectrograph that Roger Smith is building. However, we should keep in touch with him because he may be interested in joining forces if another group is taking the lead.

Kal has a colleague who is working on a slit mounted cross disperser for LBT to give echellette capabilities, and as a result he has been thinking about the possibility of doing something similar for KOSMOS and using the rest of the KOSMOS chip to provide something with higher spectral resolution.

Yuta mentioned the CHIRON spectrograph on the SMARTS 1.5m (Paul Hanley at Georgia State has been leading this). He also mentioned that aside from the echelle it would be nice to expand APO's capabilities to include polarimetry (like CFHT and Pic du Midi have done), although he recognizes that this would be tough.

Brett indicated that as a recent transplant to Switzerland he is now immersed in what the Europeans are doing, and he is willing to keep us informed on what they’re doing in an effort to help us remain competitive.

Parting thoughts: John W liked what Kevin presented to help move us forward. Nancy will create a page on the 3.5m users wiki where we can share resources and will provide a brief update of our activities at the next Users Committee meeting. We will want to solicit ideas from the broader 3.5m users community about new science drivers or other interests that may drive us forward. Kevin indicated that this is happening at some level already in a grassroots fashion.

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