NEID instrument passes Operational Readiness Review

Jun 25, 2021

On 2 June 2021 the WIYN Telescope's latest state-of-the-art instrument, the extreme precision radial velocity spectrograph called NEID, passed its Operational Readiness Review with flying colors. (NEID is short for NN-EXPLORE Exoplanet Investigations with Doppler spectroscopy, and is derived from a Native American Tohono O'odham word, pronounced NOO-id, meaning "<i>to see</i>".) This review was the final step in NASA's process for evaluating instrument performance and declaring the project a success and ready to carry out its science mission. The mission is to find Earth 2.0 – an Earth-like planet orbiting a star outside our solar system. The UW Astronomy Department's Washburn Astronomical Laboratories was part of the team funded by NASA and the National Science Foundation to build this cutting edge instrument, which incorporates novel new technologies and is designed to provide the measurement precision required to confirm such an exoplanet detection.

The NEID spectrograph being installed in the WIYN clean room
below the telescope. This photo was taken before the lid of the tank
sealed it up for operation. (Photo credit: National Optical-Infrared
Astronomy Research Laboratory/KPNO/AURA/NSF; Guðmundur Kári
Stefánsson; NEID Team/NOIRLab)

The NEID spectrograph was built by Penn State University, led by Professor Suvrath Mahadevan. The key to achieving the required precision is instrument stability over many years of repeated observations of the exoplanet at different positions in the orbit around its star. As the small planet orbits its much larger star, it imparts a slight gravitational tug on the star, causing tiny wobbles in the stellar light we observe (miniscule blueshifts and redshifts in the spectral lines, or Doppler shifts). Any change in the instrument could be indistinguishable from the infinitesimal Doppler shifts due to the exoplanet. In order to reach this stability, the spectrograph is housed inside a vacuum tank in a temperature and humidity controlled clean room beneath the WIYN Telescope. To move beyond the performance of the last generation of instruments that achieved a precision of 1 m/s, NEID has improved the control of temperature, vibration, and pressure for instrument stability, and added a calibration upgrade with the new technology of a laser frequency comb to correct any residual instabilities.

Marsha Wolf removes the cover of the bent Cassegraintelescope port onto which the Port Adapter will be installed on 21October 2019.Another important component of reaching unprecedented measurement precision is the accuracy and repeatability with which the image of the star is placed onto the optical fiber that guides the light from the telescope down to the spectrograph. This is the work of the WIYN Port Adapter, which was built by the UW Washburn Labs team, led by Dr. Marsha Wolf. This system is in some ways even more complicated than the spectrograph itself, as it has more jobs to do. The focused star image must enter the fiber in exactly the same way for every observation, as any variation leads to subtle differences in the illumination pattern on the spectrograph detector, which could be interpreted as stellar Doppler shifts. The port adapter monitors the focus and position of the image on the fiber 50 times a second and rapidly adjusts to maintain the alignment. But, that is not the port adapter's only job; it performs two additional functions that can affect observational accuracy. First, it counteracts the atmospheric dispersion of the stellar light as it passes through Earth's atmosphere, which spreads blue and red light differently within the focused image. Second, it couples light from the NEID calibration system into science fiber leading into the spectrograph with the same accuracy as the stellar image.

In January 2021 the NEID team received a NASA Group Achievement Award, which is presented to groups who have distinguished themselves through outstanding contributions to NASA's mission. The team was recognized for "the development and delivery of the state-of-the-art NEID radial velocity spectrograph and port adapter to the WIYN 3.5-meter telescope on Kitt Peak."

: Kurt Jaehnig poses next to the installed Port Adapterafter the finishing touch of adding Bucky.

The NEID instrument meets its design specification of measuring a radial velocity precision of 27 cm/s. Already during the early shared risk science period, it has measured stellar velocities down to < 40 cm/s, which is believed to be at the limit of being dominated by noise due to activity on the stellar surface, rather than effects of an orbiting planet. As deemed by the Operational Readiness Review Board, NEID is ready to carry out its 5-year mission to observe exoplanet candidates and confirm Earth analogs in the habitable zones of their stars.

The WIYN NEID Port Adapter saw first light on sky on 28October 2019. A very tired part of the team celebrates the achievementin the WIYN control room: (left to right) Michael McElwain (NASAGSFC), Jayadev Rajagopal (WIYN Executive Director), Jessica Klusmeyer(NEID Queue Observer), Marsha Wolf (UW), Sarah Logsdon (NEIDInstrument Scientist), Qian Gong (NASA GSFC).

The UW Washburn Labs NEID Port Adapter team includes:  Dr. Marsha Wolf (PI), Dr. Jeff Percival (Software Scientist), Kurt Jaehnig (Electrical Systems Engineer), Michael Smith (Mechanical Engineer), Sam Gabelt (Electronics Technician), and Cole Piddington (Machinist).

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