NEID Calibrations

Overview

The NEID Data Reduction Pipeline relies on an extensive set of instrument calibrations. Two sequences of manditory calibrations are taken each day, at 16:00 MST and at 6:30 MST. The evening calibrations are started by the night’s Queue Observer, after they have completed a series of basic functional and safety checks. The morning calibrations are automatically triggered by the NEID instrument computer. Once triggered, both sequences are fully automated. Additional calibrations are taken intermittently as required by the Queue Observer or daytime engineering and science staff. These sequences are described below.

All calibrations are tagged in the fits headers as OBSTYPE=Cal, and are available with no proprietary period.

Operational Changes

Note 1: Beginning in June 2024, the HCL exposures taken as part of the standard calibration sequence varied. ThAr exposures taken prior to June 2024 utilized HCL bulbs from Photron and the data product was quite regular. ThAr exposures from June 2024 to November 2024 utilized bulbs from a variety of vendors and the exposure times were adjusted based on the relative brightness of the lamps. During this window, UNe exposures were also taken. From November 2024 onward, only UNe are taken as part of the regular calibration sequence. We anticipate taking ThAr exposures at a cadence less frequent than daily to preserve the lifetime of our remaining ThAr bulbs.

Note 2: From June 2024 to December 2024 the Etalon was removed from NEID so it could be refurbished by its original manufacturer. During this time LFC exposures replaced Etalon exposures, and the pipeline wavelength solution module was adjusted to utilize LFCs to derive the daily instrument drift.

Note 3: In August 2024 the LFC was outfitted with a new PCF module that provides light down to ~400 nm. The blue cutoff wavelength varies from day to day, and the pipeline only utilizes light down to ~420nm. Photon counts at the blue end are extremely faint. Outside of the free-spectral-range, LFC lines rapidly become unusable.

Evening/Morning Cal. Sequence

• Dark: 5x1s

• LFC Cal-HRSky Fib: 3x60s

• Etalon Cal-HRSky Fib: 3x60s

• Etalon Cal-HRSci Fib: 3x60s

• LFC Cal-HRSci Fib:3x60s

• ThArS HR Cal-HRSci Fib: 1x480s

• UNe HR Cal-HRSci Fib: 1x480s

• LDLS HR Cal-HRSci Fib: 13x6s

• FlatBB HR Cal-HRSci Fib: 5x70s

• Flat2D: 11x60s

• LDLS HR Cal-HRSky Fib: 13x6s

• FlatBB HR HRSky Fib: 5x70s

• LDLS HESci Fib: 11x60s

• FlatBB HESci Fib: 5x70s

• Etalon HE Sci Fib: 3x60s

• LFC HE Sci Fib: 3x60s

• ThArS HE Sci Fib: 1x480s

• UNe HE Sci Fib: 1x480s

• Etalon HE Sky Fib: 3x60s

• LFC HE Sky Fib: 3x60s

• LDLS HESky Fib: 11x60s

• FlatBB HESky Fib: 5x70s

• Dark: 1x2s

Other Cals

One, two, or three 60s Etalon Cal exposures will be taken during slew and setup. The number of frames obtained is matched to the available setup time.

During normal operations, a short sequence of intermediate wavecals and flats is taken between 22:00 MST and 2:00 MST to anchor the nightly wavelength drift and flat field time series.

• Etalon Cal-HRSci Fib: 1x60s

• LFC Cal-HRSci Fib: 3x60s

• LDLS HR Cal-HRSci Fib: 13x6s

• FlatBB HR Cal-HRSci Fib: 5x70s

On certain occasions, at the discresction of the queue observer and WIYN staff, these intermediate cals may be reduced in scope. This typically occurs during long duration stares at a single target (e.g., exoplanet transit observations), where the uninterrupted data stream is deemed more critical than the additional precision afforded by these calibrations.

Last Updated: 2024-12-05, CFB