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Figure 3. JWST will explore the dark ages.

Figure 4. Hierarchical clustering models suggest that structure in the Universe begins to form on small scales, which then aggregate to build the superclusters and clusters of galaxies that we see today. The middle pane illustrates the merger process. Although hierarchical clustering has had considerable success in building up mass aggregations, work is still needed, particularly with regard to how the first stars form in low-metalicity mass aggregations.

Figure 4. Hierarchical clustering models suggest that structure in the Universe begins to form on small scales, which then aggregate to build the superclusters and clusters of galaxies that we see today. The middle pane illustrates the merger process. Although hierarchical clustering has had considerable success in building up mass aggregations, work is still needed, particularly with regard to how the first stars form in low-metalicity mass aggregations.

Understanding how today's galaxies evolved from first light objects requires more knowledge than can be provided by imaging alone. Multi-object spectroscopy is required for a statistically significant sample of galaxies spanning the redshift range over which galaxies formed. A spectral resolution, R~1000, is needed to separate diagnostic spectral lines and for estimating heavy element content and star formation rates. Moreover, NIRSpec's Integral Field Unit (IFU) will provide R~3000, 3-dimensional spectra of individual galaxies at moderate and high redshift. The IFU will provide important dynamical information on targets including active and merging galaxies.

For studying galaxies, JWST's MIRI, which also incorporates an IFU, will provide a more complete picture of galaxy structure and evolution than is possible using only near-IR wavelengths (see Fig. 5). By looking through dust (see Fig. 6) that can obscure our view of star forming regions, and imaging warm and hot dust in dense, star forming cores, MIRI will facilitate mapping the regions of galaxies that are undergoing the most intense star formation. Moreover, MIRI IFU spectroscopy will be used to diagnose the role of active galactic nuclei in the evolution of galaxies.

Figure 5. JWST's near-IR and mid-IR instruments, working together, provide essential and complementary astrophysical information. This is illustrated by the above near-IR and mid-IR composite view of the spiral galaxy M81. The 3.6 |am (left; near-IR) image is dominated by older, evolved stars. The 8 |am (middle; mid-IR) image emphasizes warm dust in the spiral arms. Finally, the 24 |am (right; mid-IR) image highlights the hot dust associated with deeply embedded star forming regions. The composite image, at bottom, clearly shows where the older, well established stars that dominate the mass are found, as well as fine structure in the spiral arms and a relatively un-obstructed view of the regions of active star formation. Credit: NASA/JPL-Caltech/K. Gordon (U. Arizona), S. Willner (Harvard/CfA), & N.A. Sharp (NOAO/AURA/NSF).

Figure 5. JWST's near-IR and mid-IR instruments, working together, provide essential and complementary astrophysical information. This is illustrated by the above near-IR and mid-IR composite view of the spiral galaxy M81. The 3.6 |am (left; near-IR) image is dominated by older, evolved stars. The 8 |am (middle; mid-IR) image emphasizes warm dust in the spiral arms. Finally, the 24 |am (right; mid-IR) image highlights the hot dust associated with deeply embedded star forming regions. The composite image, at bottom, clearly shows where the older, well established stars that dominate the mass are found, as well as fine structure in the spiral arms and a relatively un-obstructed view of the regions of active star formation. Credit: NASA/JPL-Caltech/K. Gordon (U. Arizona), S. Willner (Harvard/CfA), & N.A. Sharp (NOAO/AURA/NSF).

3) The Birth of Stars and Protoplanetary Systems: A good framework is in place for understanding how stars form and how they may form planetary systems, but a number of key steps in the process are not yet understood. JWST will work to unravel the birth and early evolution of stars, from infall onto dust-enshrouded protostars to the genesis of planetary systems. JWST needs to provide high sensitivity and high spatial resolution over a span of wavelengths that can penetrate the clouds enveloping the early stages of star formation and that can penetrate large column densities along the lines of sight through our galaxy.

Figure 6. Infrared wavelengths cut through dust that obscures our view of the visible Universe. (left) An optical wavelength image of the Eagle Nebula, M16, taken by HST. (right) A composite near-IR image (J, H, and Kshort bands) taken using the ISAAC camera on the ESO VLT ANTU telescope. Credit: (left) NASA, ESA, STScI, J. Hester & P. Scowen (Arizona State University) & (right) Mark McCaughrean & Morton Andersen, Astrophysical Institute Potsdam (AIP), and the European Southern Observatory (ESO).

4) Planetary Systems and the Origins of Life: Recent discoveries of many exosolar planets lends impetus to programs designed to characterize them. Equally important is developing an understanding of how planetary systems form, and what determines the numbers and arrangements of planets in a system. Spitzer Space Telescope discoveries of how debris disks, the likely remnants from planetary system formation, decay with time are a good illustration of how the observation of these disks tie in to the solar system and hence to planetary systems in general. JWST will be an excellent platform for studying these low surface brightness objects with high sensitivity MIRI coronagraphy. JWST will also provide a wealth of information on the surface compositions and albedos for Kuiper Belt Objects in the solar system, which will facilitate comparing what happens in debris disks with what is seen very locally. NIRCam imaging and NIRSpec spectroscopy are needed to measure absorption features from a variety of ices, while MIRI observations are needed to image the disks.

2.1 Launch and Deployment

JWST will be launched using an Ariane V rocket provided by the European Space Agency. Prior to launch, the primary mirror and other deployable elements (incl. sunshade & secondary mirror) are folded into a shroud. After launch, JWST and its sunshield will be deployed while the spacecraft is still relatively warm (see Fig. 7 for the deployment sequence). During the cruise phase to L2, the telescope and instruments will cool to reach their eventual operating temperature of ~35 K. The detectors, apart from MIRI's A,co=27 ^m Si:As SCAs, are cold-biased to operate a few degrees K above the temperature of the SI.

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Figure 7. JWST deployment. The time sequence is from left to right and from top to bottom.

Deployment steps are as follows: (1) fully deployed observatory showing partner logos, (2) JWST leaving earth following Ariane V launch, (3) beginning of deployment, (4) solar panels deploy, (5-8) sunshade deploys, (9) mast deployment, (10) secondary mirror deployment, and (11-12) primary mirror deployment. For scale, the primary mirror is about 6.5-meters in diameter and the sunshade is about the size of a tennis court.

Figure 7. JWST deployment. The time sequence is from left to right and from top to bottom.

Deployment steps are as follows: (1) fully deployed observatory showing partner logos, (2) JWST leaving earth following Ariane V launch, (3) beginning of deployment, (4) solar panels deploy, (5-8) sunshade deploys, (9) mast deployment, (10) secondary mirror deployment, and (11-12) primary mirror deployment. For scale, the primary mirror is about 6.5-meters in diameter and the sunshade is about the size of a tennis court.

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