Note to JSTAC

Garth Illingworth

Re JWST Announcement: Revised Launch Schedule to Spring 2019

Message from: Garth Illingworth
Subject: JWST announcement re revised launch schedule to spring 2019
Date: October 1, 2017

Hi Folks

I assume by now that you have heard, and probably seen the announcement, that JWST will be launched in spring 2019. See here and also below:

I got some queries re this. And also about the overlap with BepiColombo that we were hearing about.

This is not a result of any serious issues, as the announcement indicated. Broadly what was playing into this was a couple of factors:

(1) ESA’s BepiColombo mission (joint with JAXA and others) is now most likely launching in October 2018 (as ESA announced on its webpage late in 2016, but reiterated more recently and, and (2) JWST needing to work through its complex integration and test activities systematically and carefully, as noted in the NASA media release.

BepiColombo launches, as will JWST, from Kourou in French Guiana on an Ariane 5 (see BepiColombo is a mission to Mercury, and, as is typically the case with planetary missions, it has very specific and limited windows for launch. BepiColombo's earlier launch window of April 2018 could not be met and ESA then announced in a press release in November 2016 ( that they were moving the launch to October 2018. A number of folks wondered about the overlap with the JWST launch and clearly that needed to be resolved. Since BepiColomo will need to undergo a long integration period at the Kourou launch site (around 6 months), having that mission launch first is beneficial for JWST.

For JWST the cryogenic vacuum testing at JSC in Houston has gone very well and the optical telescope assembly and instruments (OTIS) are still testing but now in the warm-up phase (See While the OTIS testing has gone well, there are still many major steps in the spacecraft and sunshield Integration and Test (I&T) process, and also more major I&T activities once OTIS is mated at NGAS with the spacecraft and sunshield elements — as we heard about in our July JSTAC meeting (where we saw that the schedule reserve was down to around 3.5 months for an October 2018 launch). As the press release below noted, the overall (I&T) activities are time-consuming and are being taken carefully, systematically and thoroughly. A schedule assessment of the remaining integration and test activities led to the decision to move the launch to spring 2019. The press release also noted that the 2011 replan budget accommodates this change. IMHO this change is a wise move. JWST, as we all know, is an incredibly complex mission and given the remaining integration activities and testing it is crucial that we move forward both expeditiously, as is always needed in big projects, but also very carefully and thoroughly.

It is quite remarkable to think that since NASA's budget and schedule replan in 2011 for JWST, the mission has been on-schedule and within budget now for 6 years. To stay on schedule and within budget for 6 years is an incredible accomplishment for such a complex mission. The press release also notes that, with the revised schedule, the mission remains within budget — "Existing program budget accommodates the change in launch date,…”.

All in all, again IMHO, this outcome is win-win for both BepiColombo and for JWST. BepiColombo gets a good launch window and we have the time to work systematically and carefully through all the remaining I&T steps for JWST.


NASA Media Announcement:

Sept. 28, 2017

NASA’s James Webb Space Telescope to be Launched Spring 2019

NASA’s James Webb Space Telescope now is planning to launch between March and June 2019 from French Guiana, following a schedule assessment of the remaining integration and test activities. Previously Webb was targeted to launch in October 2018.

“The change in launch timing is not indicative of hardware or technical performance concerns,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. “Rather, the integration of the various spacecraft elements is taking longer than expected.”

As part of an international agreement with the ESA (European Space Agency) to provide a desired launch window one year prior to launch, NASA recently performed a routine schedule assessment to ensure launch preparedness and determined a launch schedule change was necessary. The careful analysis took into account the remaining tasks that needed to be completed, the lessons learned from unique environmental testing of the telescope and science instruments at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the current performance rates of integrating the spacecraft element.

Testing of the telescope and science instruments continues to go well and on schedule at NASA’s Johnson Space Center in Houston, Texas. The spacecraft itself, comprised of the spacecraft bus and sunshield, has experienced delays during its integration and testing at Northrop Grumman in Redondo Beach, California.

The additional environmental testing time of the fully assembled observatory--the telescope and the spacecraft--will ensure that Webb will be fully tested before launching into space. All the rigorous tests of the telescope and the spacecraft to date show the mission is meeting its required performance levels.

Existing program budget accommodates the change in launch date, and the change will not affect planned science observations.

“Webb’s spacecraft and sunshield are larger and more complex than most spacecraft. The combination of some integration activities taking longer than initially planned, such as the installation of more than 100 sunshield membrane release devices, factoring in lessons learned from earlier testing, like longer time spans for vibration testing, has meant the integration and testing process is just taking longer,” said Eric Smith, program director for the James Webb Space Telescope at NASA Headquarters in Washington. “Considering the investment NASA has made, and the good performance to date, we want to proceed very systemmatically through these tests to be ready for a Spring 2019 launch.”

The launch window request has been coordinated with ESA, which is providing the Ariane 5 launch of Webb as part of its scientific collaboration with NASA.

The James Webb Space Telescope is NASA’s next great multi-purpose observatory and will be the world’s most powerful space telescope ever built, serving thousands of astronomers worldwide. The 21-foot (6.5-meter) diameter infrared-optimized telescope is designed to study an extremely wide range of astrophysical phenomena: the first stars and galaxies that formed; the atmospheres of nearby planets outside our solar system, known as exoplanets; and objects within our own solar system. Webb is an international project led by NASA with its partners ESA and the Canadian Space Agency.

Last Updated: Sept. 28, 2017

Editor: Brian Dunbar