- O/IR System
The US TMT Science Working Group (SWG) and the Thirty Meter Telescope project office have compiled this page of information about the observatory, its planned instrumentation, the partnership, and potential US national participation in TMT. The FAQ was originally compiled for a community survey carried out by the SWG in September-October 2014. It is far from being comprehensive, but it should provide a useful introduction to TMT for interested scientists, and there are links to other web sites and presentations with more detailed information.
For any other questions, or if you have comments about this FAQ or TMT in general, please write to the US TMT SWG.
Primary mirror: 30m diameter, 492 hexagonal segments, f/1 focal ratio, 20 arcmin field of view.
Nasmyth focus: f/15, plate scale 0.46 arcsec/millimeter
Diffraction limited angular resolution: 0.017 arcsec at 2 microns
Site: Mauna Kea, Hawaii, was selected as the TMT site in 2009, after an extensive evaluation process. On 25 July 2014, the Hawaii Board of Land and Natural Resources approved the Mauna Kea sublease for TMT, which was the final step in the process that now allows TMT to begin construction (see press release).
Project timeline: The project is now in its construction phase, and early science operations are scheduled to begin in the 2nd quarter of 2024.
TMT is designed for extensive use of adaptive optics (AO) from the beginning of science operations. The Narrow Field Infrared Adaptive Optics System (NFIRAOS) is a multi-conjugate adaptive optics (MCAO) system that will operate with a laser guide star facility, and which will feed up to three instruments.
NFIRAOS is designed to deliver a high degree of AO correction over a 30 arcsec diameter science field, and useful (but not diffraction limited) AO correction over an unvignetted field 2 arcmin in diameter. At zenith and in median seeing conditions, the NFIRAOS Design Requirements Document (DRD) specifies maximum wavefront errors of:
This corresponds to the following minimum Strehl ratios:
|RMS wavefront error||Wavelength|
|1.0 μm||1.25 μm||1.65 μm||2.2 μm|
Potential future upgrades ("NFIRAOS+") would improve the wavefront errors to approximately 133 nm RMS over a 30 arcsec diameter field of view, corresponding to Strehl ratios of 0.50 at 1.0 μm and 0.87 at 2.2 μm.
Other NFIRAOS requirements include:
Among the first-light instruments, IRIS will use NFIRAOS to achieve diffraction-limited performance over a 15 arcsec field of view, while IRMS will benefit from AO-assisted (but not diffraction-limited) images over a 2 arcmin field of view.
References on TMT AO:
The TMT Science Advisory Committee has selected three first-light instruments for TMT that are funded as part of the construction project and will be operational when early science operations begin. They are:
Studies have been carried out for a variety of 2nd- and later-generation instruments, although none have yet been selected for development. These include:
Priorities and designs for second-generation instruments will be revisited by the TMT project, partners, and Science Advisory Committee in the relatively near future. The TMT Instrument Development Office will open in 2016, and will coordinate the development of new instruments in response to the needs of the TMT user community, with the first 2nd generation instrument expected to be delivered 2 to 3 years after early science operations begin.
References on future-generation instruments:
Slew time and target acquisition: With no change of instrument, the time between ending an exposure on one target and starting an exposure on another target anywhere on the sky, including telescope and enclosure motions, target acquisition, and guiding, is required to be less than 5 minutes. With a change of instrument, the requirement is 10 minutes.
Instrument switching and availability: all instruments are mounted on the Nasmyth platforms, and are fed by a fully articulated M3 mirror. The platforms will accommodate up to eight instruments, permanently mounted and aligned. All instruments will be kept operational except during periods of maintenance. However, it is planned that only as many as 3 to 4 instruments will be scheduled for a given night, and hence fully calibrated and supported by expert observatory support staff. Switching from one instrument to another is required to take no more than 10 minutes (see "Slew time and target acquisition" above).
Non-sidereal guiding: Enabled for rates that are up to 10% different than the sidereal rates (maximum of 16.5 arcsec per second), without significant degradation to image quality. This is a TMT system-level requirement on all necessary hardware and software components.
TMT will initially support two main observing modes:
Queue scheduling: Initially, TMT will not use observatory-wide adaptive queue scheduling. However, tools will be provided to allow adaptive scheduling within a PI- or partner-directed block of observing time. Partners may then run their own queues. TMT could implement observatory-wide adaptive queue scheduling at a future time, depending on the wishes of the partner communities, but additional staffing would be required, beyond what is in the baseline science operations plan.
Cadence observing: Programs that require monitoring observations at particular times will be accommodated in the pre-planned service observing mode (see above).
Target of opportunity (ToO): There is a TMT policy for cross-partner ToO interrupts, with detailed accounting for how ToO observing time is charged to the partners. Typical response time from trigger notification to ToO observing, including telescope slew and acquisition time, is expected to be 10 to 15 minutes.
All TMT instruments will be delivered with standard data reduction software pipelines. TMT will maintain these pipelines after a hand-off from the instrument teams. TMT will support community-led open source development and enhancement of the pipelines.
The TMT Data Archive will be the main system used by observers to retrieve their science data. It will be searchable with associated metadata and calibration frames. Science data will be accessible to all astronomers within the TMT partnership after a proprietary period, currently planned to be 18 months.
In the current TMT operations model, the observatory will not process or calibrate data for users - observers are responsible for reducing and analyzing their own data. There will be no routine pipeline processing by the observatory, and the TMT Archive will not hold reduced TMT data. Partners may establish (and fund) their own data centers, where they could carry out standardized data reduction and archive reduced data products.
In the current TMT operations plan, each TMT partner will establish and operate its own observing proposal and time allocation process. At present, there is no plan for a Master Time Allocation Committee (TAC) to oversee or coordinate telescope time allocation, or to enable coordinated proposals between partners. TMT will not check for duplication of observations between partners. Partner shares of observing time will be divided into equal amounts of bright, gray and dark time, evenly spread across each semester's available time. TMT will receive the information on time allocation from the partners and will produce a merged observing schedule for each semester. Observing time used by each partner in each lunation category will be tracked and accounted at the level of fractional hours.
The TMT International Observatory (TIO) was incorporated as a non-profit limited liability company (LLC) on 6 May 2014. The initial members of TIO are the California Institute of Technology, the National Astronomical Observatories of the Chinese Academy of Sciences, the National Institutes of Natural Sciences in Japan, and the University of California. On 24 September 2014, the government of India formally approved that country's full participation in TIO (see press release). On 6 April 2015, the office of the Prime Minister of Canada announced his government's commitment to funding TMT (see press release). The Association of Canadian Universities for Research in Astronomy (ACURA) represents Canada in TIO. As described below, the Associated Universities for Research in Astronomy (AURA) is also an Associate of TIO on behalf of the US community, but there is not yet any commitment for the NSF to provide funding for full membership in TIO.
On 22 May 2014, the TIO Board of Governors voted to proceed with the construction phase of TMT, contingent on approval of the Mauna Kea sublease. That approval was granted on 25 July, initiating the construction phase for the observatory (see press release).
Members of TIO receive TMT observing time in proportion to their contributions to construction and operations costs, with some consideration for the time at which the funds are committed to the project. The University of Hawaii (UH) will receive a 7.5% share of TMT observing time. The current TIO Members each nominally subscribe a share of approximately 10% to 20% of the available time (after subtracting time for engineering and UH). A similar share (of order 15%) is currently unsubscribed and available for additional partners.
After subtracting time for observatory activities (engineering, calibration, instrument commissioning, etc.) and the UH allocation, roughly 300 nights per year of observing time are expected to be available to the TMT partners. I.e., a 10% share (for reference) would correspond to about 30 nights of observing time per year. Partner shares of observing time would normally be divided into equal allocations in bright, gray and dark lunar conditions.
Construction: $1.2 billion in 2012 dollars, and $1.55 billion in "as spent" dollars tracking inflation and spending profiles.
Operations: $27 million per year running costs + $12 million per year for instrumentation (2012 dollars). The running costs include observatory operations and staffing, as well as data management and archiving. Instrument teams and partners are expected to identify instrumentation funding in addition to the $12M/year baseline. The TMT Operations Model was developed with a bottoms-up cost analysis including comparison to currently-operating observatories, and was externally reviewed. It is sometimes described as an "enhanced and corrected" Keck operations model.
Based on the projected construction and operations costs, a 10% share of TMT (for reference) would entail a commitment of:
In detail, real costs depend on proper accounting for the dates when the partner contributions are made and rates of inflation. If the NSF became involved on behalf of the at-large US community, it would be expected that the capital contribution would be via the NSF MREFC program and the operations costs would be borne by NSF AST.
For reference and comparison, see this summary of NSF construction and operations investments in major astronomical facilities.
Full membership in TMT International Observatory (TIO) comes with a commitment to fund the construction and operations of the observatory. The minimum commitment for full membership in TMT is a share of 5% of the construction and operations costs, or 10% for partners making in-kind contributions.
Membership in TIO provides:
The 2000 and 2010 Astronomy and Astrophysics Decadal Surveys identified the need for a Giant Segmented Mirror Telescope (GSMT) to address a wide range of forefront problems in astrophysics. US federal participation in a GSMT was listed as one of the top priority ground-based programs in both Decadal Surveys. Three GSMT projects (also known as Extremely Large Telescopes - ELTs) are now underway: The Thirty Meter Telescope (TMT), the Giant Magellan Telescope (GMT), and the European Extremely Large Telescope (E-ELT). All three expect to begin science operations in the 2020s. At a national level, the US is not currently a full partner in these projects, although several US universities and institutions are partners in TMT (Caltech; the University of California) or GMT (Carnegie Observatories; Harvard-Smithsonian CfA; Texas A&M; University of Texas at Austin; University of Arizona; University of Chicago). The University of Hawaii is granted observing time on all telescopes on Mauna Kea, including TMT.
In 2013, the National Science Foundation and TMT established a 5-year cooperative agreement after TMT's response to an NSF-AST solicitation, "Planning a partnership model for a Giant Segmented Mirror Telescope". The cooperative agreement states that "the primary deliverable of this award is to be a partnership model that might allow NSF to join the TMT Project on behalf of the US astronomical community." However, this cooperative agreement "does not imply that a GSMT will be approved for further funding."
As a consequence of this cooperative agreement, AURA is now an Associate Member of the TMT International Observatory (TIO). AURA has representatives on the TIO Board of Governors and on the TMT Science Advisory Committee (SAC). NOAO is executing the responsibilities, privileges and participation activities of AURA, representing the US-at-large astronomical community. NOAO has formed a US TMT Science Working Group (SWG), consisting of astronomers from universities and other astronomical institutions outside the current US TMT partners. The SWG is tasked to engage with the US astronomical community about TMT and potential NSF participation therein, to represent that community's interests and aspirations, and to transmit them to the TMT project, the SAC, and the Board of Governors.
The SWG and the AURA representatives to the TIO Board, working with the TMT Project, are developing a US TMT Participation Plan for the NSF. This document will discuss the science justification for US participation in TMT, as well as discussions of the telescope, instrumentation, and AO capabilities needed to address the US community's scientific aspirations for TMT. It will also discuss how the telescope would be used in order to maximize benefits for the US community, including issues of operations, scheduling, time allocation, data management and archiving, etc. Finally, there will be an integrated science and education plan, addressing broader impacts of workforce development, education, and public outreach.
As a point of reference, and for comparison to the potential cost for NSF participation in TMT, here we summarize NSF contributions to construction (through MREFC) for several major new and upcoming astronomical facilities, as well as the expected or estimated NSF share of their operations costs. This information is taken from references indicated by numbers in brackets, with links provided below.
Atacama Large Millimeter Array (ALMA):
Daniel K. Inouye Solar Telescope (DKIST, formerly ATST):
Large Synoptic Survey Telescope (LSST):
Last updated or reviewed October 30, 2015.