  The Astro Data Lab is preparing to host large spectroscopic datasets such as
a copy of the Dark Energy Spectroscopic Instrument (DESI) survey, which is
projected to include approximately 40 million spectra of galaxies and quasars
as well as over 10 million spectra of stars by 2026. Currently, we serve DR16
spectra from the Sloan Digital Sky Survey (SDSS), including Baryon Oscillation
Spectroscopic Survey (BOSS), and Extended BOSS (eBOSS) spectra. A spectral
viewer tool allows users to visually and interactively inspect spectra. Given
the large size of these spectroscopic datasets, a typical use case might
consist of a selection or query for a subset of objects of interest (e.g., a
subsample of stars or galaxies or quasars), followed by visual inspection of
the selected spectra. It is anticipated that in some cases, users will want to
go through a long list of spectra (e.g., thousands) quickly while looking for
specific features. This document contains a description of the requirements for
such a spectral viewer tool to be incorporated within the Astro Data Lab
environment at NSF's NOIRLab. For each object, the spectral viewer will display
the observed spectrum and, if available, the noise spectrum, sky spectrum, and
best-fit template spectrum. Users will be able to control the display
interactively after they launch the tool as part of their Data Lab workflow.
The primary objective will be to support the visualization of spectroscopic
datasets hosted at the Astro Data Lab but this requirements document could be a
useful reference or inspiration for other applications and/or other datasets in
the astronomy community.
