Vanessa Marquez

Development status of adjustable grazing incidence optics for 0.5 arcsecond X-ray imaging

We describe progress in the development of adjustable grazing incidence X-ray optics for 0.5 arcsec resolution cosmic X-ray imaging. To date, no optics technology is available to blend high resolution imaging like the Chandra X-ray Observatory, with square meter collecting area. Our approach to achieve these goals simultaneously is to directly deposit thin film piezoelectric actuators on the back surface of thin, lightweight Wolter-I or Wolter- Schwarschild mirror segments. The actuators are used to correct mirror figure errors due to fabrication, mounting and alignment, using calibration and a one-time figure adjustment on the ground. If necessary, it will also be possible to correct for residual gravity release and thermal effects on-orbit. In this paper we discuss our most recent results measuring influence functions of the piezoelectric actuators using a Shack-Hartmann wavefront sensor. We describe accelerated and real-time lifetime testing of the piezoelectric material, and we also discuss changes to, and recent results of, our simulations of mirror correction.

Adjustable grazing incidence x-ray optics based on thin PZT films

The direct deposition of piezoelectric thin films on thin substrates offers an appealing technology for the realization of lightweight adjustable mirrors capable of sub-arcsecond resolution. This solution will make it possible to realize X-ray telescopes with both large effective area and exceptional angular resolution and, in particular, it will enable the realization of the adjustable optics for the proposed mission Square Meter Arcsecond Resolution X-ray Telescope (SMART-X). In the past years we demonstrated for the first time the possibility of depositing a working piezoelectric thin film (1-5 um) made of lead-zirconate-titanate (PZT) on glass. Here we review the recent progress in film deposition and influence function characterization and comparison with finite element models. The suitability of the deposited films is analyzed and some constrains on the piezoelectric film performances are derived. The future steps in the development of the technology are described.

Thermal forming of glass substrates for adjustable optics (Conference Presentation)

The proposed Lynx telescope is an X-ray observatory with Chandra-like angular resolution and about 30 times larger effective area. The technology under development at SAO is based on the deposition of piezoelectric material on the back of glass substrates, used to correct longer wavelength figure errors. This requires a large number (about 8000) of figured segments with sufficient quality to be in the range of correctibility of the actuators. Thermal forming of thin glass offers a convenient approach, being based on intrinsically smooth surfaces (which doesn’t require polishing or machining), available in large quantity and at a low cost from flat display industry. Being a replica technique, this approach is particularly convenient both for development and for the realization of modular/segmented telescopes. In this paper we review the current status and the most recent advances in the thermal forming activities at SAO, and the perspectives for the employment of these substrates for the adjustable X-Ray optics.

Improved control and characterization of adjustable x-ray optics

We report on improvements in our efforts to control and characterize piezoelectrically adjustable, thin glass optics. In the past, an optical profilometer and a Shack-Hartmann wavefront sensor have been used to measure influence functions for a at adjustable mirror. An electronics system has since been developed to control > 100 actuator cells and has been used in a full calibration of a high-yield at adjustable mirror. The calibrated influence functions have been used to induce a pre-determined figure change to the mirror, representing our first attempt at figure control of a full mirror. Furthermore, we have adapted our metrology systems for cylindrical optics, allowing characterization of Wolter-type mirrors. We plan to use this metrology to perform the first piezoelectric figure correction of a cylindrical mirror over the next year.

Measuring the performance of adjustable x-ray optics with wavefront sensing

Post-mounting figure correction is a promising avenue to produce low-mass, high-resolution X-ray telescopes. We have demonstrated the feasibility of this approach using piezoelectrically adjustable glass mirrors. Influence functions for various piezoelectric cells have previously been measured with an optical profilometer, but with significant noise. We have improved on both the speed and accuracy of these measurements using a Shack- Hartmann wavefront sensing system. Additionally, we have altered our wavefront sensing system to investigate the mid frequency roughness of our slumped glass mirrors. We report on initial results for measurements of both influence functions and mid frequency roughness and describe our path forward.

Laboratory demonstration of the piezoelectric figure correction of a cylindrical slumped glass optic

The X-ray Surveyor is a mission concept for a next generation X-ray observatory. This mission will feature roughly 30 times the effective area of the Chandra Observatory while matching its sub-arcsecond angular resolution. The key to meeting these requirements is lightweight, segmented optics. To ensure these optics achieve and maintain sub-arcsecond performance, we propose to use piezoelectric coatings for post-bonding and on-orbit figure correction. We have fabricated a cylindrical prototype optic with piezoelectric adjusters and measured its performance using optical metrology. We present the results of this experiment and discuss their implications for an observatory featuring adjustable X-ray optics.

Thermal forming of substrates for the x-ray surveyor telescope

In this paper we review the progress and current status of thermal forming activities at SAO, highlighting the most relevant technical problems and the way to solve them. These activities are devoted to the realization of mirror substrates for the X-ray surveyor mission concept, an observatory with Chandra-like angular resolution and 30 times more effective area or larger. The technology under development at SAO is based on the deposition of piezoelectric material on the back of the substrates. About 8000 mirror segments, with initial quality of 10 arcseconds or better are required for the telescope.

Design, analysis, and performance verification of the interface region imaging spectrograph (IRIS) telescope primary mirror assembly

We discuss the details of the Interface Region Imaging Spectrograph (IRIS) telescope primary mirror assembly designcompared to its predecessor used in the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO-AIA) telescopes. Also included are details of the structural modeling and analysis, mirror optical surface modeling, vibration analysis, and a detailed description of the optical performance verification test program and results.The primary mirror assembly of the IRIS telescope was adapted from an existing design used on the SDO-AIA telescopes. The IRIS telescope was optimized for performance at 1369Å and 2810Å with a required 0.4 arc-second-resolution calling for a significant improvement to the mounted mirror optical surface quality over the existing SDOAIA design.To improve the optical performance, the proven bonded flexure heritage design was augmented with a novel “kinematic” mount used to secure the assembly to the telescope tube. The 200mm diameter concave mirror was fabricated from Corning ULE/RE Code 7973 EUV Premium Grade, Ultra Low Expansion Glass material and polished to better than 12ÅRMS surface roughness. The mirror is supported by three bonded titanium flexures fastened to a rigid titanium cell plate.A 25Å RMS figure error was allocated in the error budget for the mounted, coated primary mirror. The first moderesonance for the mirror was specified to be <100 Hz while surviving an expected launch load of 30G’s. The mirrorassembly was designed to operate from +14°C to +26°C with survival limits specified at -20°C to +35°C.

The Marshall grazing incidence x-ray spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument designed to obtain spatially resolved soft X-ray spectra of the solar atmosphere in the 6–24 Å (0.5–2.0 keV) range. The instrument consists of a single shell Wolter Type-I telescope, a slit, and a spectrometer comprising a matched pair of grazing incidence parabolic mirrors and a planar varied-line space diffraction grating. The instrument is designed to achieve a 50 mÅ spectral resolution and 5 arcsecond spatial resolution along a ±4-arcminute long slit, and launch is planned for 2019. We report on the status and our approaches for fabrication and alignment for this novel optical system. The telescope and spectrometer mirrors are replicated nickel shells, and are currently being fabricated at the NASA Marshall Space Flight Center. The diffraction grating is currently under development by the Massachusetts Institute of Technology (MIT); because of the strong line spacing variation across the grating, it will be fabricated through e-beam lithography.

Image stabilization for Airborne Infrared Spectrometer

The Airborne Infrared Spectrometer (AIR-Spec) took measurements of five infrared coronal emission lines from on board a NSF/NCAR airplane during the solar eclipse in August 2017. An open-loop image stabilization system was implemented using a gyroscope and fast steering mirror; 90% of the 60 millisecond exposures had an RMS jitter below 4.6 arcseconds. To increase the exposure time to 1 second, a closed-loop system is proposed using a proportional-integral-derivative (PID) controller and an image cross-correlation algorithm. We predict that 100% of 1 second exposures will have an RMS jitter below 4.6 arcseconds. A detailed analysis of the proposed closed-loop stabilization system is presented.