The James Webb Space Telescope Lives in Interesting Times



M. Mountain,

JWST has featured prominently in the space science news, and in many cases made the news in the main media, over the past few months. I look at this in two ways.  In the “glass is half full” view, the scientific case for the telescope grows stronger as the technical progress of the mission reaches new heights and gets key milestones behind us. In early June, the Institute hosted the conference, “Frontier Science Opportunities with JWST.” The meeting attracted nearly 200 astronomers from across the world to share their ideas of the groundbreaking science JWST will do. This science is the cornerstone of the Astro2010 Decadal Survey, and cannot be achieved with current or other planned facilities (Figure 1). Wendy Freedman and Jason Kalirai describe the science highlights of the meeting in an accompanying article. The community’s scientific interest in JWST can be measured by their use of the newly released JWST exposure time calculator, which has seen nearly 5,000 calculations since May 2011 (Figure 2).

Figure 1Figure 2














Seventy-five percent of JWST’s mass has been designed or is in construction, including the most challenging parts of the observatory: the 6.5-meter mirror array, the sunshield, and the instruments.  All 18 primary mirror segments have completed final polishing and, after cryo testing 12 of the mirrors, show that the average surface aberrations across the entire 6.5m mirrors at 40 K will be less than 25 nm, delivering a wavefront with less than 50nm error. When combined with all the other errors in the JWST system, this will easily allow the telescope to reach diffraction-limited performance at 2 microns, and deliver superb images even at 1 micron, as the simulation in Figure 1 shows. All of the 18 segments have also completed gold coating. There has been significant progress on the science instruments as well, as discussed in the accompanying articles “JWST Flagship” by Jason Kalirai and “NIRCam Update” by Marcia Rieke and Massimo Robberto.