NEID Extreme Precision Radial Velocity Spectrometer on Track for Installation at WIYN in 2019

Jayadev Rajagopal, NOAO

The cornerstone of a partnership between NSF and NASA to advance exoplanet science, the NEID extreme precision radial velocity spectrometer is on schedule to be installed and commissioned at the 3.5-m WIYN telescope starting in April 2019 and to be available to the community in the 2019B semester. The aggressive development and deployment schedule is dictated by the main mandate for the project: to support the NASA TESS mission, which launched in April of this year and is already producing data.

A WIYN facility instrument, NEID will be available to the exoplanet community for up to approximately 40% of the observing time on the WIYN telescope (roughly 120 nights). Proposals will be accepted through the NOAO TAC process. Additional details about the NASA-NSF partnership and the NEID spectrometer are available in a September 2016 NOAO Newsletter article. A splinter meeting on NEID has been scheduled at the January AAS meeting in Seattle, where the community can learn more about NEID’s capabilities and operation plans.

As part of the instrument development effort, NOAO has been busy designing and fabricating two major subsystems for NEID:

• Port Adaptor: A fiber feed to be mounted on the mirror cell at the Bent Cassegrain Port, the Port Adaptor will provide a highly stable, tip-tilt corrected starlight beam with image motion controlled to better than 50 milliarcseconds.
• NEID chamber: Light from the Port Adaptor will be carried by optical fibers down to the ground-floor room where NEID will be housed. The NEID chamber is tightly thermally controlled, to within a tenth of a degree throughout the year, while outside temperatures range from freezing to near 100 degrees.

Images of the NEID chamber, Port Adapter, and fiber system. Hover your mouse over the image to pause the slideshow. Click the image to step through a larger version of the slideshow, with descriptions of the images. Photos courtesy of NOAO/WIYN and Washburn Labs/University of Wisconsin.

Development Status and Highlights

The Port Adaptor optics were designed at NOAO and fabricated in Tucson by a local vendor (TORC) and are currently at the Washburn Laboratories at the University of Wisconsin (UW). UW will assemble, integrate and test all of the Port Adaptor components, including the custom Coherent Fiber Bundle (CFB) subsystem that will be used to precisely center the target on the science fiber. The CFB fibers are integrated with micron-level precision onto the science focal plane along with the science and sky fibers. Delivery of the Port Adaptor to WIYN for installation and commissioning is anticipated in March-April 2019.

At Penn State University (PSU) and other locations (U. Penn, NIST in Boulder, University of Arizona), the NEID team is fabricating and integrating various NEID components. The vacuum chamber in which the optics are to be housed has successfully undergone thermal testing that demonstrated milli-Kelvin level stability. Extreme thermal expansion control is needed to meet the requirement on radial velocity precision. A precision of 10 cm per second (the Sun’s reflex motion induced by the Earth) corresponds to the lattice separation of a few Silicon atoms on the CCD chip.

A Fabry-Perot etalon is being tested at NIST and will soon be delivered to PSU. The etalon will work with a Laser frequency Comb (LFC) to provide stringent wavelength calibration for NEID. The LFC is a turn-key device from Menlo Systems. Both systems provide a reference scale of spectral lines superposed on the target star spectrum. Calibration lamps will also be used for a robust and precise calibration process.

The NEID CCD (9K x 9K from E2V, ~10cm x 10cm) is being tested and integrated at U. Penn. An engineering grade detector has been characterized and is available for use in early integration work at PSU. Most of the major optical components including the diffraction grating, prism, and camera optics are at PSU and will soon be assembled onto the optical bench and aligned. The off-axis parabola, a vital spectrometer optic, is currently being coated.

Stay tuned for future news and highlights!