John C. Mather

Publisher’s note clarifies the correct section heading for the article.

The James Webb Space Telescope (JWST), arguably one of the most powerful and complex devices yet devised to probe the Universe, is an unusual observatory. Extremely large, deployable, not enclosed in a tube but fully open to space and located far from the Earth, it is unlike any other telescope observing in the same spectral range. It bears no resemblance to Galileo’s “eyeglass” which revolutionized our understanding of the world around us, nor to Hale’s 100-in. telescope, which transformed our view of the Universe, nor even to its modern predecessor, the Hubble Space Telescope (HST), which had thus far produced the deepest views of the Universe.

The Orbiting Configurable Artificial Star (ORCAS) mission in collaboration with the W. M. Keck Observatory has designed, assembled, built, and delivered, within 180 days, ORCAS Keck Instrument Demonstrator (ORKID) (ORCAS Keck Instrument Demonstrator), an early visible-wavelength performance demonstration with the Keck II Adaptive Optics (AO) system. The optical performance of ORKID meets the technical requirements derived from the scientific goals of having a Nyquist-sampled point spread function at 650 nm. This is achieved by diffraction-limited as-built performance with a root mean square internal wavefront error below 50 nm, which is key for the advancement of the ORCAS mission. ORKID has acquired, with a closed AO loop, no frame selection, while shifting and adding, the sharpest-ever on-sky image captured at Keck II. With a full width at half maximum of ∼15 mas, this is the equivalent of a 9-m diffraction-limited telescope. By doing so, the immense potential and viability of the proposed Hybrid Observatory ORCAS mission are demonstrated.

The Hybrid Observatory for Earth-like Exoplanets (HOEE) was uniquely proposed to search for the extremely faint Earth-like exoplanets orbiting Sun-like stars with unprecedented sensitivity and exceptional angular resolution. This concept integrates an orbiting starshade with existing ground-based telescopes for the first time. We address the major optical challenges crucial for the success of HOEE and introduce the HOEE optical model of an orbiting 99-m-diameter starshade with the 39-m European Extremely Large Telescope (E-ELT), including the forecast sensitivity analysis. We examine the optical tolerance for the starshade’s design, manufacture, deployment, and performance. The analysis includes several perturbations related to precise petal position, petal shape, petal clocking, segment position, formation flying alignment requirements, and proportional petal errors in width and length. We present a stability performance comparison with the 60-m starshade of the Habitable Worlds Observatory (HWO). We also explore the influence of the bright noise sources, including solar glint and earthshine that could potentially affect the detection of these faint habitable exoplanets. We finally discuss the effect of the Earth’s atmospheric turbulence and demonstrate the E-ELT Adaptive Optics system in mitigating these effects. The analysis suggests insignificant changes in sensitivities with the presence of medium weather conditions. These findings are leading to the innovation of the HOEE concept and establishing it as a pioneering model for opening a new window of future hybrid space-ground observatory missions.

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4 m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5 m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 yr, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.

We present the concept of using an orbiting laser as a coherent optical reference to phase a several kilometer diameter array of ground-based lasers designed to accelerate interstellar nano-spacecraft to 20% light-speed using laser propulsion. We investigate the geometrical and temporal constraints for the initial case of the target star Proxima b in the Alpha Centauri system using a laser ground site in the southern hemisphere. Based on these constraints, we detail requirements for the mission architecture for an orbiting laser to be used as an optical reference. We then present two orbits that can meet all given requirements and represent a range of engagement times and days between engagements. We also present a range of orbits with periods from 3 to 4 days and engagement times from 660 to 800 s. If desired, the orbit can be matched to the sidereal day, so each orbit period, the beacon can align with the ground station and the same target star without maneuvers. A discussion of the tradeoff between the Earth-based site latitude, time on engagement, and days between engagements is presented.

Ground-based observatories’ capabilities can be greatly enhanced by working with satellites in astrostationary orbits. Satellites inertially aligned with ground-based observatories can help mitigate atmospheric effects in astronomical, solar, and planetary observations. We present a method for developing and modeling the trajectory of potential astrostationary orbits as seen from the ground to understand whether they meet defined astrostationary conditions such as the location in the field of interest and the observation time. It discovers an L2 orbit family and shows that it can meet astrostationary conditions. It then presents an example mission, Orbiting Configurable Artificial Star (ORCAS), in which a satellite aligns with a ground-based observatory to provide near-diffraction limited observations in the visible wavelength. A highly elliptical orbit family which can meet the ORCAS requirements is studied, and we go on to show how multiple observations can be made during a single-orbit period and how specific configurations that increase the observation time can be found. Finally, other potential astrostationary families are presented, as well as additional applications that could benefit from spacecraft and ground-based observatories working together, and future work which can be done to move forward in the field is discussed.

This erratum corrects a transposition figures in the original paper. This article [J. Astron. Telesc. Instrum. Syst. 7(2), 021215 (22 March 2021) https://doi.org/10.1117/1.JATIS.7.2.021215] was originally published with Figs. 2 and 3 reversed. The figures have been put into their correct places in the paper. All versions of the article were corrected on 7 April 2021.