The NASA Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) system is designed to study the infrared emissions from star formation and active galactic nuclei through a double-Fourier Michelson interferometer located on a balloon at an altitude of 37 km. The BETTII external optics include a pair of identical beam-reducing, four-mirror telescopes, each with a 522-mm aperture, nonrotationally symmetric primary mirror. These telescopes were designed and assembled at the North Carolina State University Precision Engineering Consortium and are composed entirely of thin-walled aluminum components. The mounting structure is designed to be light weight and stiff to reduce thermal equilibration time in the rarified air at the edge of space and to maintain robust alignment of the optical elements. The mounts also prevent deformation of the large optical elements via custom-built kinematic Kelvin couplings and fixed-load clamps; the maximum form error of the optical surfaces are 300 nm RMS. This work details the design of the thin mirrors and mounting structure as well as validation of the mount assembly process, mount stiffness, and the kinematic couplings.

Future soft x-ray (10 to 50 Å) spectroscopy missions require higher effective areas and resolutions to perform critical science that cannot be done by instruments on current missions. An x-ray grating spectrometer employing off-plane reflection gratings would be capable of meeting these performance criteria. Off-plane gratings with blazed groove facets operating in the Littrow mounting can be used to achieve excellent throughput into orders achieving high resolutions. We have fabricated two off-plane gratings with blazed groove profiles via a technique that uses commonly available microfabrication processes, is easily scaled for mass production, and yields gratings customized for a given mission architecture. Both fabricated gratings were tested in the Littrow mounting at the Max Planck Institute for Extraterrestrial Physics (MPE) PANTER x-ray test facility to assess their performance. The line spread functions of diffracted orders were measured, and a maximum resolution of 800±20 is reported. In addition, we also observe evidence of a blaze effect from measurements of relative efficiencies of the diffracted orders.

The EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE) science mission concept uses a visible-wavelength phase-induced amplitude apodization (PIAA) coronagraph to enable high-contrast imaging of circumstellar debris systems and some giant planets at angular separations reaching into the habitable zones of some of the nearest stars. We report on the experimental results obtained in the vacuum chamber at the Lockheed Martin Advanced Technology Center in 10% broadband light centered about 650 nm, with a median contrast of 1×10−⁵ between 1.2 and 2.0λ/D simultaneously with 3×10−⁷ contrast between 2 and 11λ/D for a single-sided dark hole using a deformable mirror (DM) upstream of the PIAA coronagraph. These results are stable and repeatable as demonstrated by three measurement runs with DM settings set from scratch and maintained on the best 90% out of the 1000 collected frames. We compare the reduced experimental data with simulation results from modeling observed experimental limits. The observed performance is consistent with uncorrected low-order modes not estimated by the low-order wavefront sensor. Modeled sensitivity to bandwidth and residual tip/tilt modes is well matched to the experiment.

The direct imaging of exoplanet is a leading field of today’s astronomy. The photons coming from the planet carry precious information on the chemical composition of its atmosphere. The second-generation instrument, Spectro-Polarimetric High contrast Exoplanet Research (SPHERE), dedicated to detection, photometry and spectral characterization of Jovian-like planets, is now in operation on the European very large telescope. This instrument relies on an extreme adaptive optics (XAO) system to compensate for atmospheric turbulence as well as for internal errors with an unprecedented accuracy. We demonstrate the high level of performance reached by the SPHERE XAO system (SAXO) during the assembly integration and test (AIT) period. In order to fully characterize the instrument quality, two AIT periods have been mandatory. In the first phase at Observatoire de Paris, the performance of SAXO itself was assessed. In the second phase at IPAG Grenoble Observatory, the operation of SAXO in interaction with the overall instrument has been optimized. In addition to the first two phases, a final check has been performed after the reintegration of the instrument at Paranal Observatory, in the New Integration Hall before integration at the telescope focus. The final performance aimed by the SPHERE instrument with the help of SAXO is among the highest Strehl ratio pretended for an operational instrument (90% in H band, 43% in V band in a realistic turbulence r₀, and wind speed condition), a limit R magnitude for loop closure at 15, and a robustness to high wind speeds. The full-width at half-maximum reached by the instrument is 40 mas for infrared in H band and unprecedented 18.5 mas in V band.

High-resolution broadband spectroscopy at near-infrared wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar. Observations of stars were performed with the “TEDI” interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec near-infrared echelle spectrograph. These are the first multidelay EDI demonstrations on starlight, as earlier measurements used a single delay or laboratory sources. We demonstrate very high (10×) resolution boost, from original 2700 to 27,000 with current set of delays (up to 3 cm), well beyond the classical limits enforced by the slit width and detector pixel Nyquist limit. Significantly, the EDI used with multiple delays rather than a single delay as used previously yields an order of magnitude or more improvement in the stability against native spectrograph point spread function (PSF) drifts along the dispersion direction. We observe a dramatic (20×) reduction in sensitivity to PSF shift using our standard processing. A recently realized method of further reducing the PSF shift sensitivity to zero is described theoretically and demonstrated in a simple simulation which produces a 350× times reduction. We demonstrate superb rejection of fixed pattern noise due to bad detector pixels—EDI only responds to changes in pixel intensity synchronous to applied dithering. This part 1 describes data analysis, results, and instrument noise. A section on theoretical photon limited sensitivity is in a companion paper, part 2.

The displacement damage hardness that can be achieved using p-channel charge-coupled devices (CCD) was originally demonstrated in 1997, and since then a number of other studies have demonstrated an improved tolerance to radiation-induced charge transfer inefficiency when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. The initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with 10-MeV equivalent proton fluences of 1.24×10⁹ and 1.24×10¹¹  protons cm⁻² is described. The dark current, cosmetic quality, and the number of defects identified using trap pumping immediately were monitored after the irradiation for a period of 150 h with the device held at 153 K and then after different periods of time at room temperature. The device also exhibited a flatband voltage shift of around 30  mV/krad, determined by the reduction in full well capacity.

Following the unprecedented results in terms of performances delivered by the first light adaptive optics system at the Large Binocular Telescope, there has been a wide-spread and increasing interest on the pyramid wavefront sensor (PWFS), which is the key component, together with the adaptive secondary mirror, of the adaptive optics (AO) module. Currently, there is no straightforward way to model a PWFS in standard sequential ray-tracing software. Common modeling strategies tend to be user-specific and, in general, are unsatisfactory for general applications. To address this problem, we have developed an approach to PWFS modeling based on user-defined surface (UDS), whose properties reside in a specific code written in C language, for the ray-tracing software ZEMAX™. With our approach, the pyramid optical component is implemented as a standard surface in ZEMAX™, exploiting its dynamic link library (DLL) conversion then greatly simplifying ray tracing and analysis. We have utilized the pyramid UDS DLL surface—referred to as pyramidal acronyms may be too risky (PAM2R)—in order to design the current PWFS-based AO system for the Giant Magellan Telescope, evaluating tolerances, with particular attention to the angular sensitivities, by means of sequential ray-tracing tools only, thus verifying PAM2R reliability and robustness. This work indicates that PAM2R makes the design of PWFS as simple as that of other optical standard components. This is particularly suitable with the advent of the extremely large telescopes era for which complexity is definitely one of the main challenges.

The Naval Postgraduate School’s segmented mirror telescope (SMT) was developed using prototype silicon carbide active hybrid mirror technology to demonstrate lower cost and rapid manufacture of primary mirror segments for a space telescope. The developmental mirror segments used too few actuators limiting the ability to adequately correct the surface figure error. To address the unintended shortfall of the developmental mirrors, a deformable mirror is added to the SMT and control techniques are developed. The control techniques are similar to woofer-tweeter adaptive optics, where the SMT segment represents the woofer and the deformable mirror represents the tweeter. The optical design of an SMT woofer-tweeter system is presented, and the impacts of field angle magnification on the placement and size of the deformable mirror are analyzed. A space telescope woofer-tweeter wavefront control technique is proposed using a global influence matrix and closed-loop constrained minimization controller. The control technique simultaneously manipulates the woofer and tweeter mirrors. Simulation and experimental results demonstrate a significant improvement in wavefront error of the primary mirror and the control technique shows significant wavefront error improvement compared to sequentially controlling the woofer and tweeter mirrors.