Definitions of observing modes:

Classically scheduled PI science programs — Observing programs are scheduled with time assigned to individual investigators, who come to the telescopes and are responsible for carrying out the observations. Time may be assigned in units of nights or fractions of nights.

Classically scheduled PI science programs with remote observing — Observing programs are scheduled with time assigned to individual investigators, who are responsible for carrying out the observations through remote observing. Time may be assigned in units of hours or nights.

Large, community-based survey projects — Major blocks of observing time are allocated to specific survey projects that dominate the schedules of individual telescopes. Data and data products from the surveys are made available to the community in a timely way.

Service or queue observing modes — Observing programs are approved for observations, but the observations are obtained by dedicated staff observers and scheduled on a nightly or weekly basis depending on site conditions and other operational considerations.

Time domain observing modes — Observing programs are approved for observations, and observations are obtained by dedicated staff observers at time specified by the investigator to optimize the science. Time domain observing modes may include target of opportunity observations or synoptic or monitoring observations.