This PDF file contains the front matter associated with SPIE Proceedings Volume 8862 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The Solar Orbiter/METIS visible and UV coronagraph introduces the concept of occulter inversion in solar coronagraphy. Classical externally occulted coronagraphs usually have a disk in front of the telescope entrance pupil. According to the mission requirements, in order to reduce the amount of power entering the instrument and to limit the instrument dimensions, METIS is equipped with an inverted external occulter (IEO). The IEO consists of a circular aperture on the Solar Orbiter thermal shield that acts as coronagraph entrance pupil. A spherical mirror (M0), located ~800 mm behind the IEO, rejects back the disk-light through the IEO itself. A light-tight boom connects the IEO to the M0 through the thermal shield. In order to achieve high performance in stray light suppression, the IEO design needs optimization. Due to the novelty of the concept we can only use the heritage of past space-borne coronagraph occulters as a starting point to design a dedicated occulter optimization shape. A 1.5 years long, accurate test campaign has been carried out to evaluate the best optimization configuration for the IEO. Two prototypes were manufactured to take into account the impact of the boom geometry on the stray light suppression performance. Two optimization concepts were compared: the inverted cone (that derives from the conic optimization of classical occulting disks) and the serrated edge, of which several samples were manufactured, with different geometrical parameters, surface roughnesses and coatings. This work summarizes the activity we have been carrying on to define the flight specifications for the METIS occulter.

Reducing the stray light level is one of the issues that astronomical instruments have to face. In particular, the design of baffles requires special attention in order to minimize the light scattered and diffracted by the edge of the baffle's vanes. The choice of the materials and the treatments used to manufacturing those parts can significantly increase the performance of stray light suppression. This is particularly critical for instruments in which the main source of stray light is in the field-of-view and its brightness is much higher than the signal the experiment aims to measure, such as solar and stellar coronagraphs. In order to identify the best configuration to adopt in the design and manufacture of a future coronagraph, we designed a dedicated set-up that allows comparing different edge geometries and finishing in a fast and comprehensive approach. A reference edge configuration was chosen and all the other configurations were compared with it. In this paper, we describe the set-up, the characterized configurations and the obtained results.

Set to fly in the Fall of 2013 from Ft. Sumner, NM, the High Energy Replicated Optics to Explore the Sun (HEROES) mission is a collaborative effort between the NASA Marshall Space Flight Center and the Goddard Space Flight Center to upgrade an existing payload, the High Energy Replicated Optics (HERO) balloon-borne telescope, to make unique scientific measurements of the Sun and astrophysical targets during the same flight. The HEROES science payload consists of 8 mirror modules, housing a total of 109 grazing-incidence optics. These modules are mounted on a carbon-fiber and Aluminum optical bench 6 m from a matching array of high pressure xenon gas scintillation proportional counters, which serve as the focal-plane detectors. The HEROES gondola utilizes a differential GPS system (backed by a magnetometer) for coarse pointing in the azimuth and a shaft angle encoder plus inclinometer provides the coarse elevation. The HEROES payload will incorporate a new solar aspect system to supplement the existing star camera, for fine pointing during both the day and night. The overall payload will be discussed as well as the new solar aspect system. This mission is funded by the NASA HOPE (Hands On Project Experience) Training Opportunity awarded by the NASA Academy of Program/Project and Engineering Leadership, in partnership with NASA's Science Mission Directorate, Office of the Chief Engineer and Office of the Chief Technologist.

Multilayers coatings for space and solar applications are usually exposed to harsh environments. Thermal stress, ion bombardments and natural aging process can affect their performances over time. We have investigated the α–particles stability of UV and EUV optical coatings suitable for high–performance solar instrumentation. Experimental procedures, analysis and preliminary results are discussed hereafter.

METIS, the Multi Element Telescope for Imaging and Spectroscopy, is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission. The original METIS proposal included four optical paths, for observations in: 1) linearly polarized visible-light (590-650 nm), 2) narrow-band ultraviolet HI Lyman-alpha (121.6 nm), 3) narrow-band extreme-ultraviolet HeII Lyman-alpha (30.4 nm), 4) spectrographic mode for the HI Lyman- alpha and He II Lyman-alpha in corona. The design, coating performances, and test activities of the grating for the spectroscopic path are here described. The grating is optimized to work at near normal incidence and to diffract the 121.6 nm radiation at the first order and the 30.4 nm at its 4th order, consequently the two spectroscopic channels are overlapped on the focal plane. The grating is spherical with variable-line-spaced rulings, 1800 gr/mm central density. The selection of the spectroscopic channel to be acquired, either the 121.6 nm or the 30.4 nm, is made by a suitable filter wheel. The grating is multilayer-coated, to have high efficiency in both the spectral channels. In this paper we describe the tests made on a prototype with flat surface and constant groove spacing. The measures have been carried out at the BEAR beamline at the ELETTRA Synchrotron in Trieste (Italy). The grating was initially coated by gold and successively by a Mo-Si multilayer optimized at 30.4 nm. The efficiencies at the first and fourth order (121.6 and 30.4 nm) have been measured before and after the multilayer deposition. The quality of the multilayer deposition has been tested by atomic force microscope measurements on the grating surface and by reflectivity measurements performed on a test reference mirror. The experimental data are compared with numerical simulations accounting for the coating roughness and the smoothening effect on the blaze profile after the multilayer deposition. To our knowledge, this is the first time that such a grating configuration is proposed.

PROBA-3 is a technology mission of the European Space Agency (ESA), devoted to the in-orbit demonstration of formation flying techniques and technologies. Presently in phase B, PROBA-3 will implement a coronagraph (called ASPIICS, “Association de Satellites Pour l'Imagerie et l'Interferometrie de la Couronne Solaire”) that will both demonstrate and exploit the capabilities and performance of formation flying. ASPIICS is distributed on two spacecrafts separated by 140m with the external occulting disk hosted by one spacecraft and the telescope (optical camera included) on the other one. ASPIICS will perform high spatial resolution imaging of the solar corona from the coronal base (1.04 solar radii) out to 3 solar radii. ASPIICS is developed by a large consortium of European Institutes and Industries from Belgium, Czech Republic, France, Germany, Greece, Italy, Luxembourg and Russia. The design studies concern the external occulter mounted on one satellite and the telescope on the other one but also the additional metrology tools that will help checking the formation and ensure that the flight configuration is optimal for observations. PROBA-3/ASPIICS successfully passed the Preliminary Design Review (PDR) in April 2013 and is currently in the implementation phase C/D. The present paper will provide the current status of PROBA-3/ASPIICS, a description of the instrument and its expected performance.

Since more than 20 years, Laboratoire Charles Fabry and Institut d’Astrophysique Spatiale are involved in development of the EUV multilayer coating for solar imaging. Previous instruments, such as the SOHO EIT and STEREO EUVI telescopes, employed the Mo/Si multilayer coatings, which offered at that time the best efficiency and stability. We present here recent results of the development of highly efficient EUV multilayers coatings at 17.4 nm and 30.4 nm for the Solar Orbiter mission. New multilayer structures, based on a combination of three materials including aluminum, have been optimized both theoretically and experimentally. We have succeeded to reduce interfacial roughness of Albased multilayers down to 0.5 nm via optimization of the multilayer design and the deposition process. The EUV peak reflectance of Al/Mo/SiC and Al/Mo/B₄C multilayer coatings reaches 56% at 17.4 nm, the highest value reported up to now for this wavelength. We have also optimized specific bi-periodic structures that possess two reflection bands in the EUV range with high spectral selectivity. The EUV reflectivity of these Al-based dual-band coatings are compared with the Si/Mo/B₄C baseline coating for Solar Orbiter. Since the stability of reflecting multilayer coating is an important issue for space missions, we have also studied the temporal stability as well as the resistivity of the coatings to thermal cycling and to proton irradiation. Experimental results confirm that Al/Mo/SiC and Al/Mo/B₄C multilayer coatings are good candidates for the Solar Orbiter EUV imaging telescopes.

This paper describes develop of a two channel echelle spectrograph, Solar Chromospheric Flare Spectreograph (SCFC), to observe the optical spectra at the locations of ares and explosive events on the Sun. The SCFS will record are spectra in two channels in the wavelength range of 350-890 nm, which has several chromospheric spectral lines. The SCFS will have a multi-fiber based slit capable of observing at 100 locations of the active region magnetic field polarity inversion lines. The field of view of SCFS will be 80 x 80 arc sec with spatial resolution of 8 arc sec. The spectral resolution of 60,000 will be adequate for measuring Doppler velocities of about 5 km s^-1. The instrument is designed using off-the-shelves optical and mechanical parts with minimum fabrication at an in-house machine shop. The SCFS will be integrated with the full-disk Ha telescope at the Big Bear Solar Observatory that is operating semi-automatically around the year except for weather interruptions. The SCFS observations will be mainly used to study the physics of flares, but part of the time will be devoted to classroom educational activities.

Long-exposure spectroscopy and spectro-polarimetry at near-infrared wavelengths is one of the preferred tools deployed to measure the physical properties of Solar Prominences, including the Prominence magnetic field. However, until now, it was not possible to observe Prominences in sufficient detail to allow us to understand their dynamical properties. In order to understand Solar prominences, we need to observe them at sub-arcsecond spatial resolution, with a temporal cadence sufficient to make highly transient structures visible. Adaptive Optics capable of locking-on to off-limb prominence structure has the potential of providing diffraction limited spectroscopy and polarimetry of prominence structure. Such an adaptive optics system will allow scientists to come one step closer to understanding the true nature of solar prominences. In this presentation, we will detail the design and construction of such a system.

The 4m Advance Technology Solar Telescope (ATST) will be the world's leading ground-based resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and variability in the Sun's output. The project has entered its construction phase. Major subsystems have been contracted, designs are complete, and fabrication has started. As its highest priority science driver ATST shall provide high resolution and high sensitivity observations of the dynamic solar magnetic fields throughout the solar atmosphere, including the corona at infrared wavelengths. A high order adaptive optics system delivers a corrected beam to the initial set of state-of-the-art, facility class instrumentation located in the Coudé laboratory facility. The initial set of five first generation instruments consists of imagers and spectro-polarimeters. Development and construction of a four-meter solar telescope presents many technical challenges, including thermal control of the enclosure, telescope structure and optics and wavefront control. A brief overview of the science goals and observational requirements of the ATST will be given, followed by a summary of the status of the telescope, its instrumentation, and the construction of the facility.

The ESA/NASA Solar Orbiter mission will address the central question of heliophysics: How does the Sun create and control the heliosphere? The heliosphere represents a uniquely accessible domain of space, where fundamental physical processes common to solar, astrophysical and laboratory plasmas can be studied under conditions impossible to reproduce on Earth and unfeasible to observe from astronomical distances. In this paper, we present a brief overview of the mission.

SPICE is a high resolution imaging spectrometer operating at extreme ultraviolet wavelengths, 70.4 – 79.0 nm and 97.3 - 104.9 nm. It is a facility instrument on the Solar Orbiter mission. SPICE will address the key science goals of Solar Orbiter by providing the quantitative knowledge of the physical state and composition of the plasmas in the solar atmosphere, in particular investigating the source regions of outflows and ejection processes which link the solar surface and corona to the heliosphere. By observing the intensities of selected spectral lines and line profiles, SPICE will derive temperature, density, flow and composition information for the plasmas in the temperature range from 10,000 K to 10MK. The instrument optics consists of a single-mirror telescope (off-axis paraboloid operating at near-normal incidence), feeding an imaging spectrometer. The spectrometer is also using just one optical element, a Toroidal Variable Line Space grating, which images the entrance slit from the telescope focal plane onto a pair of detector arrays, with a magnification of approximately x5. Each detector consists of a photocathode coated microchannel plate image intensifier, coupled to active-pixel-sensor (APS). Particular features of the instrument needed due to proximity to the Sun include: use of dichroic coating on the mirror to transmit and reject the majority of the solar spectrum, particle-deflector to protect the optics from the solar wind, and use of data compression due to telemetry limitations.

This presentation outlines a general optical design for coronagraphs working in both the visible-light (VL) and UV/EUV wavelength ranges by combining the use of reflective, multilayer-coated or interference-coated optics with Lyot stops. This design has been successfully applied to a sub-orbital coronagraph. Another version of this novel design for visiblelight/ EUV coronagraphs uses an inverted-occultation design in order to minimize the solar flux entering the instrument. This design has been used for the coronagraph – METIS - on board the ESA Solar Orbital mission. The current optical configuration of METIS adopted for the Solar Orbiter mission includes Visible-light and UV imaging. However, the innovative inverted-occultation concept is flexible enough that it can also accommodate a EUV spectrograph maintaining the same basic optical layout. The paper also describes the potential capabilities of the inverted-occulter coronagraph as a VL/UV imager and EUV spectrograph for future solar missions.

The SoloHI instrument for the ESA/NASA Solar Orbiter mission will track density fluctuations in the inner heliosphere, by observing visible sunlight scattered by electrons in the solar wind. Fluctuations are associated with dynamic events such as coronal mass ejections, but also with the “quiescent” solar wind. SoloHI will provide the crucial link between the low corona observations from the Solar Orbiter instruments and the in-situ measurements on Solar Orbiter and the Solar Probe Plus missions. The instrument is a visible-light telescope, based on the SECCHI/Heliospheric Imager (HI) currently flying on the STEREO mission. In this concept, a series of baffles reduce the scattered light from the solar disk and reflections from the spacecraft to levels below the scene brightness, typically by a factor of 10¹². The fluctuations are imposed against a much brighter signal produced by light scattered by dust particles (the zodiacal light/F-corona). Multiple images are obtained over a period of several minutes and are summed on-board to increase the signal-to-noise ratio and to reduce the telemetry load. SoloHI is a single telescope with a 40⁰ field of view beginning at 5° from the Sun center. Through a series of Venus gravity assists, the minimum perihelia for Solar Orbiter will be reduced to about 60 Rsun (0.28 AU), and the inclination of the orbital plane will be increased to a maximum of 35° after the 7 year mission. The CMOS/APS detector is a mosaic of four 2048 x 1930 pixel arrays, each 2-side buttable with 11 μm pixels.

The Solar Probe Plus (SPP) mission scheduled for launch in 2018, will orbit between the Sun and Venus with diminishing perihelia reaching as close as 7 million km (9.86 solar radii) from Sun center. In addition to a suite of in-situ probes for the magnetic field, plasma, and energetic particles, SPP will be equipped with an imager. The Wide-field Imager for the Solar PRobe+ (WISPR), with a 95° radial by 58° transverse field of view, will image the fine-scale coronal structure of the corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. Given the tight mass constrains of the mission, WISPR incorporates an efficient design of two widefield telescopes and their associated focal plane arrays based on novel large-format (2kx2k) APS CMOS detectors into the smallest heliospheric imaging package to date. The flexible control electronics allow WISPR to collect individual images at cadences up to 1 second at perihelion or sum several of them to increase the signal-to-noise during the outbound part of the orbit. The use of two telescopes minimizes the risk of dust damage which may be considerable close to the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first ‘local’ imager providing a crucial link between the large scale corona and the in-situ measurements.

The Naval Research Laboratory is developing next generation CMOS imaging arrays for the Solar Orbiter and Solar Probe Plus missions. The device development is nearly complete with flight device delivery scheduled for summer of 2013. The 4Kx4K mosaic array with 10micron pixels is well suited to the panoramic imaging required for the Solar Orbiter mission. The devices are robust (<100krad) and exhibit minimal performance degradation with respect to radiation. The device design and performance are described.

The upcoming Solar Probe Plus (SPP) mission requires novel approaches for in-situ plasma instrument design. SPP’s Solar Probe Cup (SPC) instrument will, as part of the Solar Wind Electrons, Alphas, and Protons (SWEAP) instrument suite, operate over an enormous range of temperatures, yet must still accurately measure currents below 1 pico-amp, and with modest power requirements. This paper discusses some of the key technology development aspects of the SPC, a Faraday Cup and one of the few instruments on SPP that is directly exposed to the solar disk, where at closest approach to the Sun (less than 10 solar radii (R_s) from the center of the Sun) the intensity is greater than 475 earth-suns. These challenges range from materials characterization at temperatures in excess of 1400°C to thermal modeling of the behavior of the materials and their interactions at these temperatures. We discuss the trades that have resulted in the material selection for the current design of the Faraday Cup. Specific challenges include the material selection and mechanical design of insulators, particularly for the high-voltage (up to 8 kV) grid and coaxial supply line, and thermo-optical techniques to minimize temperatures in the SPC, with the specific intent of demonstrating Technology Readiness Level 6 by the end of 2013.

The Solar Probe Cup (SPC) Instrument is a Sun-facing Faraday Cup instrument slated for launch aboard the Solar Probe Plus (SPP) spacecraft in 2018. SPC is one of two instruments onboard the Solar Wind Electrons Alphas Protons (SWEAP) instrument suite and is the only SPP charged particle instrument that will not be shielded behind the spacecraft’s Thermal Protection System (TPS). The 7-year SPP mission will take SPC on 24 solar encounters at perihelia ranging from 35 to 9.86 solar radii (R_S). The SPC components will encounter a large range of temperatures, from in excess of 1500°C at perihelion to -130°C at or near aphelion. This paper details the derived mechanical and structural requirements on the primary SPC mechanical assemblies including its thermal shield, the sensor unit and the strut/adapter assembly. An example of sensor requirements derivation to the component level is provided by the modulator flex ring. Preliminary requirements derivation, definition, and compliance are provided for these assemblies and components.

This paper describes the implementation of a solar simulator, know as the Solar Environment Simulator (SES), that can simulate solar flux levels up to those encountered at 9.8 solar radii. The paper outlines the design, and the challenges of realizing the SES. It also describes its initial uses for proving out the design of the Solar Winds Electrons, Alphas, and Protons (SWEAP) Faraday cup. The upcoming Solar Probe Plus (SPP) mission requires that its in-situ plasma instrument (the Faraday Cup) survive and operate over an unprecedented range of temperatures. One of the key risk mitigation activities during Phase B has been to develop and implement a simulator that will enable thermal testing of the Faraday Cup under flight-like conditions. While still in the initial start-up, the SES has proven to be an instrumental component in the process of predicting the inflight performance of the SWEAP Faraday Cup. With near continuously variable power control above the threshold of 1.6kW/lamp up to approximately 6.5kW/lamp, the SES has been used to determine the system response to a wide range of incoming flux, thereby making it possible to correlate detailed thermal models to a high degree of certainty (see Ref. [1], Figure 1.1). The SES consists of a set of repurposed, and slightly re-designed standard movie projectors. The projectors have proven to be an economical and effective means to safely hold and control the xenon short-arc lamps that are the basis of the SES. This paper outlines the key challenges controlling the extremely high flux levels (~70w/cm^2) necessary to make the SES a useful test facility.

The Solar Radiation and Climate Experiment (SORCE) is a NASA-sponsored Low-Earth-Orbit satellite mission providing measurements of incoming x-ray, ultraviolet, visible, near-infrared and total solar radiation. SORCE is currently in its 10th year of operation. The Spectral Irradiance Monitor (SIM) instrument has been providing daily solar spectrum covering the wavelength range from 240 to 2400 nm at a resolution between 0.60-33 nm using a single optical element. SIM was designed to provide an absolute accuracy of < 2% over the wavelength coverage and a goal of longterm accuracy of 0.03% per year. The exposure of the optics, detectors and electronics to the harsh space environment causes changes in their properties. With the very high accuracy goals, it is critical to keep track of these changes as precisely as possible throughout the lifetime of the mission. We will be reviewing the methods used to track and correct for SIM instrumental degradation of the optics and the detectors since the start of the mission. We will also discuss lessons learned in the design of long lived solar observing missions and how they were applied to the SIM instrument on the coming Total Solar Irradiance Sensors (TSIS) mission.

We present an overview of solar sounding rocket instruments developed jointly by NASA Marshall Space Flight Center and the University of Alabama in Huntsville. The High Resolution Coronal Imager (Hi-C) is an EUV (19.3 nm) imaging telescope which was flown successfully in July 2012. The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) is a Lyman Alpha (121.6 nm) spectropolarimeter developed jointly with the National Astronomical Observatory of Japan and scheduled for launch in 2015. The Marshall Grazing Incidence X-ray Spectrograph is a soft X-ray (0.5-1.2 keV) stigmatic spectrograph designed to achieve 5 arcsecond spatial resolution along the slit.

The solar UV imager (SUVI) is an extreme ultraviolet instrument that will fly on the Geostationary Operational Environmental Satellite (GOES)-R and-S platforms, as part of NOAA’s space weather monitoring fleet. It will provide important information on solar activity and the effects of the Sun on the earth and the near-earth environment. This instrument will image the full solar disc in 6 EUV wavebands between 303.8 Å and 93.9 Å. A generalized Cassegrain telescope configuration is employed where six mirror sectors utilize multilayer coatings optimized for the six wavelengths of interest. An aperture shutter is used to select the appropriate sector for observations at a particular wavelength. A thinned, back-illuminated CCD sensor with 21μm (2.5 arcsec) pixels resides in the telescope focal plane. The modulation transfer function (MTF) is usually considered to be the image quality criterion of choice for applications where fine detail in extended images needs to be specified or evaluated. However, the contractual image quality requirement was specified in terms of fractional ensquared energy for a variety of different wavelengths and square sizes. In this paper we will calculate and present MTF plots (as degraded by diffraction, geometrical aberrations, surface scatter effects and detector effects) for each of the SUVI wavelengths of interest. Surface scatter due to residual optical fabrication errors is a major factor limiting the performance at the shorter wavelengths, and the large detector size severely limits the performance at all SUVI wavelengths.

Solar flares accelerate particles up to high energies (MeV and GeV scales for electrons and ions, respectively) through efficient acceleration processes that are not currently understood. Hard X-rays (HXRs) are the most direct diagnostic of flare-accelerated electrons. However, past and current solar HXR observers lack the necessary sensitivity and imaging dynamic range to make detailed studies of faint HXR sources in the solar corona (where particle acceleration is thought to occur); these limitations are mainly due to the indirect Fourier imaging techniques used by these observers. With greater sensitivity and dynamic range, electron acceleration sites could be systematically studied in detail. Both these capabilities can be advanced by the use of direct focusing optics. The recently own Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload demonstrates the unique diagnostic power of focusing optics for observations of solar HXRs. FOXSI features grazing-incidence replicated nickel optics with ~5 arcsecond resolution and fine-pitch silicon strip detectors with a ~7.7 arcsecond strip pitch. FOXSI flew successfully on 2012 November 2, producing images and spectra of a microflare and performing a search for non-thermal emission (4{15 keV) from nanoflares occurring outside active regions in the quiet Sun. A future spacecraft version of FOXSI, featuring similar optics and detectors, could make detailed observations of HXRs from flare-accelerated electrons, identifying and characterizing particle acceleration sites and mapping out paths of energetic electrons as they leave these sites and propagate throughout the solar corona. This paper will describe the FOXSI instrument and present images from the first flight.

We present a design progress of the Solar UV-Vis-IR Telescope (SUVIT) aboard the next Japanese solar mission SOLAR-C. SUVIT has an aperture diameter of ~1.4 m for achieving spectro-polarimetric observations with spatial and temporal resolution exceeding the Hinode Solar Optical Telescope (SOT). We have studied structural and thermal designs of the optical telescope as well as the optical interface between the telescope and the focal plane instruments. The focal plane instruments are installed into two packages, filtergraph and spectrograph packages. The spectropolarimeter is the instrument dedicated to accurate polarimetry in the three spectrum windows at 525 nm, 854 nm, and 1083 nm for observing magnetic fields at both the photospheric and chromospheric layers. We made optical design of the spectrograph accommodating the conventional slit spectrograph and the integral field unit (IFU) for two-dimensional coverage. We are running feasibility study of the IFU using fiber arrays consisting of rectangular cores.

We present science and development activities of the soft X-ray photon-counting spectroscopic imager for the solar corona that we conceive as a possible scientific payload for the Japanese Solar-C mission. The imager employs a grazing-incidence sector mirror of Wolter-I type with which images of the corona are to be taken in a wide temperature range (1 MK to beyond 10 MK) with the highest-ever angular resolution (0.5"/pixel for a focal length of 4 m) as an Xray telescope for the Sun. Moreover, by employing a back-thinned CMOS image sensor as the focal-plane device, we attempmt to implement photon-counting capability with which imaging-spectroscopy of the X-ray corona will be performed for the first time, in the energy range from ~0.5 keV up to 10 keV. The imaging-spectroscopic observations will provide totally-new information on mechanism(s) for magnetic reconnection, generation of supra-thermal electrons in the reconnecting magnetic structure during flares, and for the generation of hot coronal plasmas (heated beyond a few MK) which may be responsible for the formation of the hot cores of solar active regions.

METIS is a visible and UV externally inversely occulted coronagraph selected to fly aboard the Solar Orbiter space mission. Thanks to its own capabilities and exploiting the peculiar opportunities offered by the SO mission profile, the instrument will address some of the still open issues in understanding the physics driving the observed processes in the corona and characterizing the slow and fast components of the solar wind. Recently the METIS design went thorough a significant revision involving the overall electronics configuration and software functionalities, comprehensive of descoping of some features but also aiming at the improvement of the instrument’s reliability. As a result the electronics architecture has been simplified enabling an effective cold-strapped redundancy scheme of some subsystems, while the preliminary SW database has been defined as well. We also identified the scientific processing algorithms implementing the instrument functionalities and the imagecompression capabilities able to match the selected HW resources providing an optimal compromise between complexity and compression ratio. This paper describes the revised electronics and software design developed in order to maximize the overall scientific returns with the updated instrument configuration approaching the Phases C/D of the project.

Hard X-ray and gamma-ray emission during solar flares encode information about electron/ion dynamics and provide a proxy to deduce solar atmospheric parameters. Enhanced imaging, spectroscopy and polarimetry of HXR/gamma-ray are emissions over ~20 keV to greater than or approx. equal to 10MeV is needed to study particle transport; the Gamma-Ray Imager/Polarimeter for Solar Flares (GRIPS) instrument is designed to meet these goals. GRIPS' key technological improvements over the current solar state of the art in HXR/gamma-ray energies (RHESSI) include 3D position-sensitive germanium detectors (3D-GeDs) and a single-grid modulation collimator, the Multi-Pitch Rotating Modulator (MPRM). The 3D-GeDs allow GRIPS to reconstruct Compton-scatter tracks of energy deposition, providing enhanced background reduction and polarization measurements. Each of GRIPS' sixteen detectors has 298 electrode strips, each of which has dedicated ASIC/FPGA electronics. In GRIPS' energy range, indirect Fourier imaging provides higher resolution than focusing optics or Compton imaging techniques. The MPRM grid-imaging system has a single-grid design which provides 2x the throughput of a bigrid imaging system like RHESSI. Quasi-continuous resolution from 12.5 - 162 arcsecs is achieved by varying the grid pitch between 1 - 13mm. This spatial resolution will be capable of imaging the separate footpoints in a variety of flare sizes. In comparison, RHESSI's minimum 35 arcsec resolution at the same energy makes footpoints resolvable in only the largest flares. We discuss GRIPS' science goals, the instrument overall, and recent developments in GRIPS' detector and imaging systems. GRIPS is scheduled for an engineering flight from Fort Sumner in September 2014, followed by two long-duration balloon flights from Antarctica in 2015/16.

METIS, the Multi Element Telescope for Imaging and Spectroscopy, is the solar coronagraph foreseen for the ESA Solar Orbiter mission. METIS is conceived to image the solar corona from a near-Sun orbit in two different spectral bands: in the HI UV narrow band at 121.6 nm, and in the polarized visible light band (580 – 640 nm). METIS is an externally occulted coronagraph which adopts an “inverted occulted” configuration. The inverted external occulter (IEO) is a small circular aperture after which a small spherical mirror M0 rejects back the disk-light through the IEO, then an annular mirror collects the signal coming from the corona and redirects it toward the telescope secondary mirror. This paper presents the error budget analysis for this new-concept coronagraph configuration, which incorporates two different sub-channels: the UV imaging and the polarimetric visible one. The two sub-channels are sharing the telescope optics, then an interference filter transmits the UV light towards the UV detector, while the visible-light is reflected towards the polarimetric unit. The tolerance analysis is rather complex, in fact not only the optical performance for the two sub-channels has to be maintained simultaneously, but also the positions of the M0 and the occulters (IEO, internal occulter and Lyot stop), which assure the optimal disk light suppression, have to be taken into account as tolerancing parameters. To guarantee the scientific requirements are optimally fulfilled for the two sub-channels, the preliminary results of manufacturing, alignment and stability tolerance analysis for the whole instrument will be described and discussed.

VUV polarimetry has been recognized as one of the most powerful diagnostic tools for remote sensing of the solar corona, with the potential of providing accurate space resolved information on magnetic activity through observation of resonance lines of the most abundant species. In an on-going collaboration between our groups from Spain and Italy, a program to design, build and characterize optical components for the VUV region has been activated. In particular, using the beamline BEAR at the synchrotron facility Elettra in Trieste (Italy) we have characterized some thin film reflecting linear polarizers, designed and optimized for the study of polarimetric properties of the HI Ly-alpha at 121.6 nm. The characterizations are performed from 100 to 150 nm at different angles of incidence (40 – 80 deg). Some polarizers have shown excellent performances with an average reflectivity R ≈ 34% and a modulation factor exceeding 95%. The calibration of several samples is reported and aging effects on some old samples is discussed. One of the calibrated sample will be used for the evaluation of the performances of a new fast calibration set-up facility for VUV.

METIS is the UV/VIS coronagraph of the ESA mission Solar Orbiter. One of the main technical drivers of the instrument is the detailed stray-light control, as close to the disk edge the VIS coronal emission is six to about seven order of magnitudes lower than the disk one. The instrument testing procedure must then include a measurement of its stray-light rejection capability, which is a fundamental step in the whole instrument calibration / acceptance process. A preliminary optical design of the optical light source for stray-light test is presented. The main requirements are discussed and two possible solutions are outlined.