We propose an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO). Gravitational waves can be observed by comparing a pair of atom interferometers separated by a 30 km baseline. In the proposed configuration, one or three of these interferometer pairs are simultaneously operated through the use of two or three satellites in formation flight. The three satellite configuration allows for the increased suppression of multiple noise sources and for the detection of stochastic gravitational wave signals. The mission will offer a strain sensitivity of < 10 −18 / √ Hz in the 50 mHz-10 Hz frequency range, providing access to a rich scientific region with 123 1954 J. M. Hogan et al. substantial discovery potential. This band is not currently addressed with the LIGO, VIRGO, or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Finally, we present a brief conceptual overview of shorter-baseline ( 100 m) atom interferometer configurations that could be deployed as proof-of-principle instruments on the International Space Station (AGIS-ISS) or an independent satellite.

We review the operating principles of noncollinear acousto-optic tunable filters (AOTF's), emphasizing the use of two orthogonally polarized beams for narrow-band imaging. Spectral characterization and spectral broadening measurements of commercially available AOTF's agree with theoretical predictions and reveal difficulties associated with imaging noncollimated light. An AOTF imaging spectropolarimeter for ground-based astronomy that uses CCD's has been constructed at NASA Goddard Space Flight Center. It uses a TeO(2) noncollinear AOTF and a simple optical relay assembly to produce side-by-side orthogonally polarized spectral images. We summarize the instrument design and initial performance tests. We include sample spectral images acquired at the Goddard Geophysical and Astronomical Observatory.

The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5 layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wave front sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.

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