The Webb Science Timeline

I. Neill Reid,, and Janice Lee,

NASA’s Great Observatories have flourished by providing an open forum for astronomers worldwide to propose and execute science projects spanning a wide range of scales. Hubble, in particular, has supported 6,623 investigators from 49 US states and 37 countries over the past 26 years through either observing programs or archival research, with over $750 million in funding for US investigators. NASA’s next Great Observatory, the James Webb Space Telescope, is scheduled for launch in less than two years, in October 2018, and will continue the tradition of democratizing access to high-impact science data.

Commissioning and EROs

Webb is a complex telescope with sophisticated instrumentation and a correspondingly extensive commissioning program. The initial spacecraft (SC) commissioning occupies the 31 days following launch. During that time, Webb transitions to a halo orbit at L2, the deployment is completed and various systems, including the science instruments (SI), are powered up. The subsequent 3 months are devoted to commissioning the Optical Telescope Element (OTE), i.e., aligning the mirrors. Once aligned, the science instruments are commissioned, culminating with the execution of the NASA Early Release Observations (EROs)—observations of targets chosen to have a wide public appeal, demonstrating the high-level capabilities of Webb instruments, but not chosen for award-winning science potential. EROs should not be confused with the more extensive Early Release Science (ERS) program outlined below. Substantive observations for instrumental calibration are unlikely to be obtained during commissioning, but will be obtained throughout Cycle 1. The full commissioning phase is expected to be completed within 180 days.

Observing Proposals

Webb observing programs will be scheduled against wall-clock time, including statistical components for slews and observatory overheads such as calibration observations and momentum dumps. Up to 10% of each cycle will be assigned to Director's Discretionary (DD) programs, with the Director's Discretionary Early Release Science (DD-ERS) program accounting for the bulk of DD time allocated in Cycle 1 (see this Newsletter for an article on DD-ERS by Janice Lee, and an accompanying Frequently Asked Questions article by Janice Lee and I. Neill Reid). As with Hubble, the community may submit proposals for DD time throughout the cycle for follow-up observations of transient phenomena. The remaining time in the first three cycles is divided between Guest Observer (GO) programs and time allocated to Guaranteed Time Observers (GTOs): the Instrument Principal Investigators (PIs), Interdisciplinary Scientists, the Telescope Scientist, and their teams in recognition of their contributions to developing the Webb project over the past decade and a half. GTOs will receive 4,020 hours distributed over the first three cycles, i.e., ∼16% of the time available during that period. GTO programs will likely account for ∼2,000 hours in Cycle 1, leaving at least 5,500 hours for GO programs. In comparison, Hubble offers ∼3,500 orbits or ∼3,100 hours of observing time in a typical cycle.

While Webb Cycle 1 science observations may not occur until approximately 6 months after launch, the planning of those observations starts much earlier (Figure 1). The GTO Call for Proposals will be issued on January 6, 2017, with the deadline for submitting Cycle 1 observing programs on April 1, 2017. The GTO Cycle 1 reserved observations will be published no later than June 15, 2017. Neither ERS nor Cycle 1 GO programs may duplicate those observations without an appropriate scientific justification, such as astrometric or photometric monitoring; a duplicate observation is an observation of the same target using the same instrument mode with an on-target exposure time within a factor of 4 of the previously scheduled observation. Similarly, Cycle 2 GTO programs may not duplicate Cycle 1 GO observations without a specific justification. This restriction is not designed to "protect" science programs, but to maximize the efficient use of Webb observing time.

Figure 1: Webb Cycle 1 proposal submission and review schedule.

The schedule for soliciting and reviewing DD-ERS programs is described in detail elsewhere in this Newsletter issue (see the article on DD-ERS by Janice Lee, and an accompanying Frequently Asked Questions article by Janice Lee and I. Neill Reid). In brief, proposers must submit a Notice of Intent, due on March 3, 2017; the proposal deadline is August 18, 2017; and the TAC will meet to review the proposal in mid-October 2017. The Call for Proposals for Cycle 1 GO programs will be issued on November 30, 2017, with the proposal deadline currently scheduled for March 2, 2018. Files submitted via the Astronomer's Proposal Tool (APT) for accepted DD-ERS programs and for GTO programs will be made available to the general community as templates to guide GO submissions. GO proposals will be subject to peer review by the Telescope Allocation Committee, whose members will be drawn from the general community maintaining appropriate representation from the USA, Canada, and ESA countries. The TAC meeting will be held in mid-May 2018.

We anticipate structuring the Webb Cycle 1 GO proposal review in a manner similar to the current Hubble process. The majority of the available time will be set aside for regular proposals reviewed by mirrored topical panels covering broad subject areas, with the aim of achieving a balanced distribution in science areas. Those panels will also review medium-scale proposals, with the time for those proposals drawn from a separate pool. Finally, Cycle 1 will provide an opportunity for the community to submit requests for Large and Treasury programs; a panel comprising the panel chairs, at-large members, and the TAC Chair will review those proposals. We anticipate setting aside more than ∼1,000 hours for Large/Treasury programs in Cycle 1, with the proportion of time devoted to those programs increasing in future cycles.

Most Webb observations (GO and GTO) will have default exclusive access (proprietary) periods. Exceptions are Large, Treasury, and DD programs, including the DD-ERS, where the default period will be zero. All GO and GTO proposers have the option of requesting an exclusive access period that differs from the default; in the case of GO programs, the TAC will adjudicate the justification for any such request.

Figure 2: The Hubble and Webb proposal submission and review schedules for 2017 through 2020.

Coordination with Other Facilties

Joint proposals for Webb observations with other facilities will not be solicited in Cycle 1. However, the Hubble proposal schedule is being adjusted to accommodate the Webb proposal process, and provide an opportunity for the community to propose for Hubble observations that complement accepted Webb Cycle 1 programs. In recent years, the Call for Hubble proposals has been issued in January, with the proposal deadline in April and the TAC meeting in June. That cadence has the potential to produce destructive interference with the Webb Cycle 1 schedule in 2018. To resolve this conflict, the Cycle 25 TAC, meeting in June 2017, will pre-allocate ∼40% of Cycle 26 programs; the remainder of the Cycle 26 orbits will be allocated by a ∆TAC that will meet in September 2018. The Cycle 26 Call will be restricted to Medium and Large/Treasury programs, enabling proposals that complement accepted Webb Cycle 1 programs. The Cycle 26 Mid-Cycle Call will provide an opportunity to propose smaller-scale programs.

In summary, Webb's launch may still be two years distant, but the first opportunities to propose observing programs will arrive much sooner. The Institute is developing on-line resources and collaborating with other institutions to organize a comprehensive set of workshops and dedicated sessions at larger meetings, including the summer and winter AAS meetings, focused on providing the community with training to support proposal preparation and submission (see adjacent Newsletter articles in this issue). We encourage the community to take advantage of those opportunities and fully exploit Webb's scientific capabilities.