L1 — Science and facility requirements#

Spectroscopy#

  • Wavelength coverage. ZShooter shall provide simultaneous spectroscopic wavelength coverage spanning 0.31–2.45 µm. Continuous coverage across atmospheric gaps is not required.

  • Spatial resolution. ZShooter shall support natural seeing and delivered seeing-enhanced point-spread functions down to 0.3 arcsecond FWHM.

  • Slit length. ZShooter shall support 10 arcsecond long-slit spectroscopy.

  • Spectral resolution. ZShooter shall deliver a mean resolving power of at least 18,000 under median natural-seeing conditions and 40,000 under supported seeing-enhanced conditions, using a slit matched to the delivered image quality.

  • Sensitivity. At blaze peak and R = 1,000, ZShooter shall achieve a signal-to-noise ratio of at least 5 per resolution element in one hour of on-target integration for an AB-magnitude 24.5 point source under supported seeing enhancement and an AB-magnitude 23.5 point source under natural seeing. Verification in OH-affected regions and K band shall use the adopted sky-line and emissivity model.

  • Stability. ZShooter shall limit instrument-contributed radial-velocity error, for spectra with sufficient photon-limited radial-velocity information, to the greater of 200 m/s or 1/60 of a native resolution element when reduced using calibration data acquired within four hours of the science exposure. For spectra reduced to R = 1,000 using calibration data acquired within 48 hours, the absolute radial-velocity error shall not exceed 7.5 km/s.

Operations#

  • Operational efficiency. ZShooter shall be available for timely and remote follow-up observation of transient sources, enabling science exposure initiation of a prepared ToO observation within five minutes after delivery of the target beam. A single operator shall be able to configure the instrument, acquire and guide on the target, control exposures and sequences, obtain calibrations, and assess data quality. Supported operations include user-selectable nod sequences and independent exposure and readout cadences among spectrograph channels.

  • Lifetime. ZShooter shall have an operational lifetime of seven years at WMKO before requiring major refurbishment.

Imaging#

  • Imaging capability. ZShooter shall offer at least three simultaneous imaging bands with sufficient field for 1% relative photometry across 80% of the observable sky in median-seeing conditions. The required bands are u, i, and one selectable intermediate band.

  • High-speed imaging. ZImager shall support windowed fast-mode imaging at ≥100 Hz, with a goal of ≥1 kHz, in a subfield containing the science target and at least one comparison star, in at least two bands simultaneously.

  • Absolute timing. ZImager shall provide GPS-synchronized per-frame absolute timing with accuracy ≤1 ms, with a goal of ≤50 µs.

  • Differential photometry. ZImager shall deliver ≤1% differential photometric precision in high-speed mode for sources with per-frame S/N > 50, using an in-field comparison star.

  • Limiting magnitude. Under median natural-seeing conditions, ZImager shall achieve a 5σ point-source detection in a 15-minute exposure to 26 AB mag in each supported imaging band.

Calibration and data#

  • Spectrophotometric fidelity. Reduced data shall preserve relative flux calibration among spectrograph channels and between the spectrograph and each imaging band, with systematic error no greater than 10%, and shall support absolute normalization using imaging or spectrophotometric standards.

  • Data products. ZShooter shall automatically produce baseline reduced products for every supported observing mode.

  • OH suppression. ZShooter shall facilitate observations between bright night-sky lines and suppress stray light from those lines.

  • Low-resolution capability. ZShooter shall provide spectra binned to a resolving power of 1,000 from every spectroscopic configuration.