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Observing Modes and Time Allocation


TMT will provide a service to the TIO Members. The TIO Members, not TMT directly, are in control of the allocation of telescope time to science programs. Members may choose to coordinate time allocation between themselves for large programs, smaller discovery programs, ToO programs, etc.

The main science operations goal for TMT, on behalf of the TIO Members, will be to operate the facility and its science instrument 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 execution of their approved programs. Science operations will be implemented in a remote manner, from a science operations headquarter located at sea-level. 

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. The queue mode itself will require the development of adaptive tools able to prioritize in realtime the programs to execute based on meteo conditions, scientific priorities, partners share of telescope time and science program completeness. The use of laser guide stars on the mountain will also require some tools to be developed and implemented to manage potential conflicts between the execution of science programs from all facilities present on the mountain. 

Time Allocation

Members control their share of time, and TIO will specify the number of observing nights/year (distributed proportionately throughout the phases of the moon and length of night) that will be allocated to each Member. Each Member is responsible to determine how it will use its observing time, 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 time-allocation processes. Partners are free to choose to coordinate their time-allocation processes to optimize the science return of large programs or allocate time independently of other partners or some combination.

Service Mode/Queue 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, pre-planned time-critical programs and large programs that are spread over a long period of time. The service observing mode is particularly well adapted to programs demanding observing conditions (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), whose occurrence probability is low, of the order of a few percents typically.

Eavesdropping Mode

In "Eavesdropping Mode", the program is executed by the Observatory staff, like for a “service mode” program, but a science team-member is in communication with the Observatory staff via some videoconferencing tools to help with realtime decisions. The typical types of programs benefitting from this mode would be short time-critical programs, whose difficulty rely on an astronomical event of short duration (transit, occultation, etc) but with a highly critical timing component. The science team member will be able to connect to the Observatory user environment using tools developed for use on a personal computer connected to a fast internet connection, or possibly by traveling to a nearby TMT remote operations center, if such facilities become available in the future across 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 headquarters (or possibly to a remote operations center) to actively participate in the implementation of their observing program, which would have been pre-scheduled for execution at a specific period of the telescope planning. Typical programs benefiting from such a mode are complex programs regarding their target acquisition, 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 in progress. To support ToO programs, observatory policies and practices for interrupts will be developed, and are expected to include fully automated rapid implementation of pre-arranged programs via automatic triggers from other facilities.

Time critical programs for short-timescale events

Service mode observing can easily accommodate observations of events that can be forecast in the future, such as exoplanet transits, binary star eclipses, asteroid occultations, etc.. Time resolved observing modes with high accuracy timestamps are being considered as instruments and observatory subsystems are being designed and built.

Large-scale Programs

Large-scale / long-term programs are expected to be carried out as part of the TMT observing program. These programs will be cross-partner collaborative programs, where each partner contributes a fraction of the time used for the observing program.

Data archives and instrument pipelines
Science, calibration, engineering 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 be available to the user immediately after collection, through the archive web interfaces. Science data will be subject to proprietary periods and will be stored indefinitely in the TMT archive. Engineering, meteorological and subsystem status information will also be archived and available to users. Tools will be made available to query the data archive via a system based on the International Virtual Observatory Simple Image Access service.

Dedicated instrument pipelines and instrument simulators

Dedicated instrument pipelines will also be made available to reduce science data by removing instrumental and atmospheric signatures and to extract their science information. 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. Although quick-look data will be provided by the observatory to help with real-time decision and data quality assessment, full data reduction and science ready data product extraction will be the responsibility of the users (TMT staff expertise will be available to support this activity).

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. Observing scenarios with combinations of differentially moving non-sidereal and sidereal guide and/or wavefront sensor targets can also be supported.

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 be monitored and used for optimizing the sequence of execution of the science programs.