olution Spectrograph ( HRS ) at the Southern African Large Telescope . Table 1 provides a summary of MAROON-X ’ s properties . We intend to bring MAROON-X to Gemini North as a visiting instrument beginning in 2019 .
Current Status
In January 2017 , KiwiStar Optics delivered the core spectrograph and the blue wavelength arm to the University of Chicago . This has been installed in a chamber with temperature control to better than 20 milliKelvin ( Figure 1 ). The spectrograph is currently undergoing an intensive test and calibration campaign . All the expected characteristics of the spectrograph ( e . g ., resolution , scattered light , and efficiency ) have been confirmed with lab measurements .
The spectrograph ’ s efficiency in the blue arm is particularly impressive , with peak throughputs from the exit of the fiber feed to the focal plane of over 60 % ( Figure 2 ). Initial testing is being done with only the blue wavelength arm implemented and a smaller , off-the-shelf 2k x 2k e2v detector in place of
January 2018 / 2017 Year in Review the final 4k x 4k custom STA science detector systems that will be used on the telescope . Orders for the red arm and the final detector systems have been placed and delivery is expected for mid-2018 . One of the detectors is a thick , deep-depletion CCD that offers quantum efficiencies of over 90 % out to 900 nm to fully exploit the high throughput of the instrument and to suppress fringing which would otherwise limit the achievable radial velocity precision .
The primary wavelength calibrator for the instrument is a stabilized Fabry-Perot etalon , traced to the hyperfine transition of rubidium . This device delivers a comb-like spectrum of about 500 bright and unresolved lines per spectral order with frequencies traceable to a few cm / s ( Stürmer et al ., 2017 ). In addition , an automated solar telescope delivers solar light to the spectrograph , to test and improve the data reduction and radial velocity analysis pipeline delivered with the instrument ( Figure 3 , on the next page ).
First tests with the etalon calibrator demonstrated that even over the limited spectral coverage of the smaller and less stable lab detector system , the science and calibration fibers track each other to better than 20 cm / s over timescales of minutes to days ( Figure 4 , on the next page ). The high line density and exquisite stability of the etalon allows for unprecedented stability vetting and calibration at a level otherwise offered only by a much more complex and expensive laser frequency comb .
GeminiFocus
Figure 1 . MAROON-X spectrograph installed in its environmental chamber in the lab at the University of Chicago . Credit : Andreas Seifahrt for the MAROON-X team .
Figure 2 . Efficiency curves for the MAROON-X spectrograph from the fiber exit to the focal plane . The measured efficiency for the as-built spectrograph ( arrows ) are lower limits only due to limitations in resolving the blaze peak of each echelle order in a spectrophotometric setup . A model based on the measured throughput of all individual components is shown as the blue line . For comparison we show the theoretical predictions from an optical model with minimum and best-effort specs for the throughput and efficiency of all optical components . The delivered optics exceed the best case expectations over most of the bandpass of the blue arm and lend confidence in achieving similar efficiencies in the red arm , currently under construction at KiwiStar Optics .
61