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James Webb Space Telescope (JWST) Guaranteed Time Observations (GTO) are awarded to scientists who deliver key JWST components.  Initial JWST Cycle 1 GTO proposals and descriptions of observations are due on April 1, 2017. Finalized JWST Cycle 1 GTO observation descriptions and targets will be publicly released by June 15, 2017

Late Breaking News

June 21, 2017: APT 25.2 Released

APT version 25.2 has been released:

You can read What's New on, and watch training videos on


June 15, 2017: GTO Observation Plans Released

The GTO observing plans for Cycle 1 have been released, detailing over 2100 observations on numerous investigations. The observations are summarized by science topic on JWST GTO Observation Specifications, with more detailed specifications tabulated by instrument.

June 2, 2017: APT 25.1.1 and ETC 1.1 Released

APT version 25.1.1 has been released:

You can read What's New on, and watch training videos on

In addition, JWST ETC version 1.1 features faster performance, new target acquisition modes, improved timing models, and more: see the Release Notes for details.

As a note, when you log in to the ETC 1.1, your old workbooks will be marked "Out of Date":

  • When you load them, they will open in Read-Only mode: this ensures that your version 1.0 results are not overwritten and remain available to you for reference.
  • If you copy an out of date workbook, and load the copy, all its calculations will be automatically updated for you with the current version of the software.
  • For more information, see "ETC 1.1 and Out-of-Date Workbooks"

About This Document

Guaranteed Time Observations (GTO) reward both individuals and teams of scientists who were selected to deliver of key hardware and software components, or technical and inter-disciplinary knowledge for JWST. The program provides a total of about 16% use of the observatory over the first 3 cycles of operation. See the section JWST Cycle 1 GTO Proposal Submission Policies for information on who is eligible to submit, observing time requirements (including overheads), data rights, restrictions on types of observations, and other policy information.

Each JWST GTO is required to submit a description of the proposed Cycle 1 science program, including specific targets and specific observations using the templates provided. Those observations specifications will be reviewed and revised, and are required to be finalized at a date at least two months before the Cycle 1 GO Call is released, at which time the specifications will be made public. At the same time, GTOs must develop detailed observing proposals, which are required to be submitted using the Astronomer’s Proposal Tool.  The Cycle 1 GTO proposal submission process, therefore, has three stages: (1) preparation of the Science Descriptions and Observation Specifications templates(2) finalizing reservations for publishing observing specifications, and finally (3) Astronomer's Proposal Tool (APT) submissions for technical review and revisions. The section JWST Cycle 1 GTO Proposal Submission Process describes this process in full.

Important Dates

Stage 1

Release of the Cycle 1 call for GTO proposals

January 6, 2017

Cycle 1 GTO Science Descriptions and Observation Specifications due

April 1, 2017


APT version 25.2 Released (with final Cycle 1 overhead calculations)

June 1, 2017

Stage 2

GTO Observation Specifications Published (public)

June 15, 2017

Stage 3

GTO APT Technical Reviews and Revisions

July 28–November 15, 2017

Changes in observations communicated to SMO/STScINovember 15, 2017
Final APT proposal submissionby November 30, 2017

Public advertisement of GTO APT files

December 15, 2017

GTO Stage 1 Proposal and Observation Description Templates

Teams should complete the GTO Observation Specification Workbook [.xlsx] to provide descriptions of their observations for Cycle 1. The Guide to the Observation Specification Worksheet [.docx] gives brief details on the fields in each worksheet of the workbook. A GTO Proposal [.docx] should accompany the workbook, to provide general science summaries, coordinated parallel justifications (if applicable), and the breakdown of total hours to charge which programs. If you prefer, you may use this alternative total time charge table [.xlsx], provided by Pierre Ferruit.

 The proposal abstracts will be made public in the stage 2 release of the observation specifications.

Who's Responsible

Members of the Science Mission Office at STScI are responsible for the oversight of the JWST science program selection process. The members involved include Neill Reid (Associate Director for Science and Head of the Science Mission Office), Louis-Gregory Strolger, and Technical Manager Brett Blacker.

Where to Get Help

Submit questions to the JWST helpdesk at  Consult JWST documentation at, and see for additional tools and resources.