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Observing Modes and Time Allocation

Overview

TMT will provide a set of dedicated science user services to all TIO Members that will encompass all aspects of proposal handling, from the science time proposals are prepared and submitted for review, to their selection, implementation and execution at the Observatory, and finally the ingestion of all scientific data into a science archive populated with high-level reduced data-products. Individual TIO Members will be in control of their own telescope time allocation process, though Members may choose to coordinate telescope time requests in a collaborative manner for large programs, but also for smaller discovery programs, ToOs, etc.

The main science operations goal for TMT, on behalf of the TIO Members, will be to operate the facility and its science instruments at maximum efficiency, maximizing the observing time available and the outcome of the science programs. To reach this goal, several observing modes will be made available for the execution of TMT science programs, all using the most modern observing support tools to enhance observing efficiency.

The facility and its science systems (telescope and active optics, laser guide star facility, science instruments) will be operated by the TMT staff, who will support the science teams in the preparation and execution of their approved programs. Science operations will be implemented in a remote manner, from science operations Headquarters located at sea-level. TMT Members might decide to develop their own remote observing nodes to support their community of science users, though the control of the science instruments and telescope will always remain within the sole responsibility of the TMT science operations staff located at the sea-level TMT Headquarters.

Whatever the selected mode of observations, high-end operations tools will be developed to support the observatory staff and science team members in the preparation and execution of TMT’s science programs, and of course towards the analysis of the science data collected. Service mode observations (science programs scheduled in queue mode) will be carried out using adaptive scheduling tools able to prioritize in realtime the execution of science programs based on meteo conditions, scientific priorities, program time-criticality, partners share of telescope time and science program completeness. The use of laser guide stars on the mountain will also require the implementation of laser traffic control systems to manage potential conflicts between the execution of science programs from all facilities present on the mountain. 

Time Allocation

TIO Members will control their share of telescope time based on the number of observing nights/year (distributed proportionately throughout the phases of the moon and length of night) allocated to each Member. Each Member is responsible to determine how it will use its observing time among the various observing modes proposed (visitor, service, eavesdropping), including cooperation on large cross-Member programs, Target of Opportunity (ToO) programs, etc. The observatory will operate on behalf of its Members and will not be a standalone scientific center.

Each Partner will be responsible for their own time-allocation processes although collaboration among Partners will be encouraged to optimize the science return of large programs.

Service Mode

Service Mode is often referred to as Queue Mode. In Service Mode, programs are executed entirely by the observatory science operations staff, without realtime involvement of the science team members. This mode requires that all information regarding the observing strategy and instrument set-up has been provided, processed and approved by the observatory ahead of time. The service observing mode can easily accommodate synoptic observations, cadence observing, time-critical programs, ToO programs or large programs whose execution is spread over a long period of time. The service observing mode is particularly well adapted to programs demanding observing conditions whose occurrence probability is low, of the order of a few percents typically (like seeing better than 0.5”, or long coherence time of the atmospheric turbulence, or dry atmospheric episodes with precipitable-water-vapor lower than 1mm).

Eavesdropping Mode

"Eavesdropping Mode" is a special case of service mode during which the program is executed by the Observatory staff while a science team-member is in communication with the Observatory staff via videoconferencing to help with realtime decisions. The typical types of programs benefitting from this mode would be short-duration time-critical programs, whose difficulty rely on rapid astronomical events (transit, occultation, etc) with a highly critical timing component. Using his/her personal computer, itself connected to a fast internet service provider, the science team member will be able to remotely connect to the Observatory environment with tools developed to that effect. The eavesdropping user could also possibly travel to the closest TMT remote operations node, if such remote observing facilities become available throughout the TMT partnership. 

Visitor Mode/Classical Mode

In Visitor Mode, also sometimes named "Classical Mode", one or several persons from the science team will travel to the TMT science operations Headquarters (or possibly to a remote observing node) to actively participate in the execution of their observing program, which would have been scheduled at a specific period of the observing cycle. Typical programs benefiting from the visitor mode are programs with complex target acquisition, or with a strong component of real-time decision making, or whose observing strategy relies on a realtime analysis of the data obtained. 

Time critical and ToO Programs
  • Target of Opportunity Programs

TMT’s capability for rapid object acquisition (10 minutes maximum requirement on “telescope preset”, which includes the time needed for telescope slewing, target acquisition, AO and instrument configuration, up to the beginning of science observations) and the range of Nasmyth observing-ready instrumentation allow effective execution of Target of Opportunity (ToO) programs such as follow-up and characterization of GRBs, SNe and gravitational wave sources. Procedures for exploiting ToO will be fully integrated into all observing modes.  ToO observations can occur at any time unless ‘protected’ observations such as time-critical observations are already in progress. To support ToO programs, observatory policies and practices for interrupts will be developed, and are expected to include fully automated rapid execution of ToO programs via automatic triggers.

  • Time critical programs for short-timescale events

Service mode observing can easily accommodate observations of time-critical events that can be forecasted in the future, such as exoplanet transits, binary star eclipses, asteroid occultations, etc.. Time-resolved observations with high-accuracy timestamps of the data produced are fully implemented in the design and construction of TMT science instruments and observatory subsystems.

Large-scale Programs

Large-scale and/or long-term programs are expected to be carried out as part of TMT's observations. These programs might be cross-partner collaborative programs, for which each partner contributes a fraction of the total observing time needed.

Data archives and instrument pipelines
  • Science, calibration and meteorological data

Science data includes all scientific data obtained by TMT science instruments, together with their corresponding calibration data, their associated metadata and ancillary data (e.g. mask definition files, AO PSF information). They will become available to the user immediately after collection, through a science archive web interface. Science data will be subject to proprietary periods and will be stored indefinitely in the TMT science archive. Meteorological data will also be archived and available to science users. Tools will be made available to query the science archive via a system based on the International Virtual Observatory Simple Image Access service.

  • Dedicated instrument pipelines and instrument simulators

In addition to populating the science archive with fully reduced data (instrumental and atmospheric signatures removal, extraction and calibration of the scientific information), all instrument pipelines will be made available to TMT users who want to pursue themselves the processes involved in the data-reduction and extraction of their science data . Observation simulators will also be delivered with each instrument, to both help with the preparation of observing programs, and to estimate the observing time required to reach the sensitivity level specific to each program.

Observing efficiency/target acquisition/non-sidereal tracking

The TMT requirement for telescope preset  is 10 minutes maximum.  This includes telescope slewing, target acquisition and AO and instrument configurations, up to the beginning of science observations. There are separate target acquisition time requirements related to observing programs that involve small telescope moves and reconfiguration of the same instrument (e.g. changing a multi-object slit mask or re-establishing Laser Guide Star and AO operation on a neighboring field), and all these requirements are set to allow the most efficient program execution.

The observatory has a top level requirement to support observations of targets moving at up to ±10% of the sidereal rate. All of the wavefront sensor systems are designed to track natural guide stars whilst the science target moves relative to the background stars.

Site Conditions Monitoring system

The Site Conditions Monitoring System (SCMS) will provide atmospheric turbulence information to allow optimal scheduling of AO and seeing limited programs. Cloud conditions, precipitable water vapor and other meteorological parameters will also be monitored by the SCMS and used for optimizing the execution of science programs. All SCMS data will be accessible to users through the science archive as well as a dedicated web interface for realtime conditions monitoring.