Preparing for the First James Webb Space Telescope Proposals

Klaus Pontoppidan,1

The integration and testing of the James Webb Space Telescope is on schedule for a nominal October 2018 launch, and recently its beautiful mirror assembly was revealed in the clean room at NASA’s Goddard Space Flight Center (GSFC). This means that we are now a year from the first open call for proposals for observing with Webb—namely the Early Release Science (ERS) program call—planned for May 2017. The ERS is a program awarding approximately 500 hours of observing time early in Webb Cycle 1 to exciting science programs for immediate release to the astronomical community. Following this, a call for the full Cycle 1 General Observer program will be issued in November 2017.

Anyone responding to these opportunities will have the use of a comprehensive set of planning tools. The first flight-ready systems to be made available include the Astronomer's Proposal Tool (APT), the Exposure Time Calculator (ETC), various simulators and other helper tools, as well as a wide-ranging user documentation system. In spring 2017, all tools necessary for planning science observations for Cycle 1 will be released. We are excited to see the hard work that has gone into developing the Webb ground system over the past years now come to fruition, as all the planning tools are being polished in preparation for Webb science.

How do I observe with Webb? The new Webb documentation system

The user documentation for Webb is under active development, and it will look quite different from Hubble’s documentation. The system, informally called JDOX, uses a Wikipedia-like format, in which a large number of topical, self-contained, and hyperlinked articles are available on a fully online repository.

Figure 1: Screenshot from the new Webb documentation system.

The information is organized following the “Every Page is Page One” style.2 EPPO is a system designed specifically for technical documentation where typical users are searching for specific pieces of information, rather than reading a comprehensive handbook front-to-back. JDOX will release articles incrementally, as they become available, starting with information needed for proposal planning, such as background articles for every instrument, followed by proposal planning articles. Data processing and analysis articles will follow later. The first JDOX release is planned for early summer 2016.

Along with the documentation release, we have published a new Webb website, which contains more information about the proposal process, links to the various tools and news items.3

Figure 2: The new Webb website at the Institute.

Scripting Webb: The first operational builds of the Webb Proposal Tool

The Proposal and Planning System (PPS) “build 13” was completed in April, and will be undergoing testing in the next months. This is the build that supports commissioning and the target selection for Guaranteed Time Observations (GTOs). The next build (14) is the flight build supporting the GO Cycle 1 call for proposals, and is due for delivery to integration and testing in the fall of 2016. The formal release of the APT flight build for Webb is slated for spring 2017, although preliminary versions are already available for download. APT now includes an intelligent model for estimating overheads (called “smart accounting”), which takes into account how close visits within a given program are distributed on the sky to appropriately charge users with the actual slew time needed to execute their programs. A new visibility tool has also been developed for Webb, which graphically displays the time windows within which a given visit can be scheduled.

What’s the performance? Release of the Webb ETC

The Exposure Time Calculator (ETC) development team reached a major milestone in March, as the implementation of all the Webb science modes was completed. The Webb ETC, informally called “Pandeia,” is a new general Exposure Time Calculator tool and simulator, which models an observatory and instrument package by constructing full three-dimensional astronomical scenes and “observes” them with a model instrument, producing two-dimensional detector-plane products and methods for extracting signals, such as spectra or photometry. Pandeia consists of a Python engine, which calculates sensitivities, and a web application, which provides a powerful user interface for using the ETC. The Webb ETC is currently undergoing quantitative verification and testing. The full web application is due to be released in January 2017. To give the community access to Webb sensitivity calculations as soon as possible, a beta version of the engine will be released in May 2016 as an installable Python package. The ETC engine also allows for scripting and extensive parameter studies.

Figure 3: Webb ETC calculation for the NIRISS Single-Object Slitless Spectroscopy (SOSS) mode, showing two orders of the same source.

When the Exposure Time Calculator is not enough

There are aspects of planning for Webb science where more advanced simulations than basic ETC calculations are needed, so several simulators are being prepared for general release. STIPS is the simulator for the Webb imaging modes with NIRCam and MIRI. It calculates full-field simulated data products for populations of stars and galaxies. An exoplanet transit observation simulator for the community, using the Webb ETC engine, is under development by Natasha Batalha (Penn State University), and will also be accessed through a web application.

Webb update: Assembling a spacecraft

The Webb integration and testing reached several major milestones this spring. The final instrument-level cryogenic vacuum test (CV3) was completed at NASA’s Goddard Space Flight Center (GSFC), and a comprehensive analysis of the data obtained during the test is underway. Overall, the observatory is healthy and the CV3 test is considered a great success. The assembly of the optical telescope was completed (including the installation of all primary mirror segments, the secondary and the aft optics). Keep a close eye on the GSFC cleanroom webcam in the next few months to see the telescope with the dust covers taken off in preparation for various tests! The next major step is the integration of the instrument module (ISIM) into the optical telescope (OTE), forming the combined Optical Telescope Element and Integrated Science (OTIS), which is due to be tested at NASA’s Johnson Space Flight Center (JSC) in 2017.

The construction of the Mission Operations Center (MOC) at the Institute was completed, and it is ready for use training flight operations personnel. In flight, Webb will be operated from the MOC, and telemetry from the spacecraft will arrive there via the Deep Space Network.

Figure 4: The Webb Mission Operations Center at the Institute.

1 James Webb Space Telescope Deputy Project Scientist, Space Telescope Science Institute