White-light Thomson scattering observations from the Solar Mass Ejection Imager (SMEI) have recorded the inner heliospheric response to many CMEs. Here we detail how we determine the extent of several CME events in SMEI observations (including those of 28 May 28 and 28 October, 2003). We show how we are able to measure these events from their first observations as close as 20° from the solar disk until they fade away in the SMEI 180° field of view. We employ a 3D reconstruction technique that provides perspective views from outward-flowing solar wind as observed at Earth. This is accomplished by iteratively fitting the parameters of a kinematic solar wind density model to the SMEI white light observations and to Solar-Terrestrial Environment Laboratory (STELab), interplanetary scintillation (IPS) velocity data. This 3D modeling technique enables separating the true heliospheric response in SMEI from background noise, and reconstructing the 3D heliospheric structure as a function of time. These reconstructions allow both separation of the 28 October CME from other nearby heliospheric structure and a determination of its mass. Comparisons with LASCO for individual CMEs or portions of them allow a detailed view of changes to the CME shape and mass as they propagate outward.

The LASCO-C2 coronagraph on-board the SOHO solar observatory has been providing a continuous flow of coronal images for the past nine years. Synoptic maps for each Carrington rotation have been constructed from these images and offer a global view of the temporal evolution of the solar corona, particularly the occurrence of transient events such as the coronal mass ejections (CMEs), an important component of space weather activity. CMEs present distinct signatures on synoptic maps offering a novel approach to the problem of their statistical detection. We are presently testing several techniques of automatic detection based on their morphological properties. The basic procedure involves three steps: i) morphological characterization, ii) definition and application of adapted filters (optimal trade-off filters, Canny filter,...), iii) segmentation of the filtered synoptic maps. At this stage, the CMEs are detected. The efficiency of the detection of the various filters is estimated using the ROC curves. On-going studies include the classification of CMEs based on their physical properties, the determination of their velocities, and the question of their connection to the streamer belt.

The glow of interstellar plasma and solar wind pickup ions and solar wind emissions at 30.4 nm provide a way of exploring important physical processes in the heliosphere. Imaging the heliosphere at this wavelength with high spectral resolution will map the heliopause, probe pickup ions in the solar wind, and reveal the three-dimensional flow pattern of the solar wind, including in the regions over the sun's poles. The required high-throughput, high-resolution spectrometer for diffuse radiation should be able to measure 1 milli-Rayleigh irradiance in 10000 seconds with a 0.005-nm spectral resolution across pixels subtending a few degrees of celestial arc. The desired performance characteristics can be achieved by combining multiple entrance slits with an optimized spectrometer design. We present a concept of a space experiment to image the heliosphere at 30.4 nm and discuss the scientific rationale and required instrumentation.

The four-meter Advanced Technology Solar Telescope (ATST) will be the most powerful solar telescope and the world's leading resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and variability in the Sun's output. Development of a four-meter solar telescope presents many technical challenges, which include: thermal control of optics and telescope structure; contamination control of the primary mirror to achieve low scattered light levels for coronal observations; control of instrumental polarization to allow accurate and precise polarimetric observations of solar magnetic fields; and high-order solar adaptive optics that uses solar granulation as the wavefront sensing target in order to achieve diffraction limited imaging and spectroscopy. We give a status report of the ATST project focusing on the substantial progress that has been made with the design of the ATST. We summarize the design of the major subsystems, including the enclosure, the primary and secondary mirror assemblies, the coude and Nasmyth focal stations, adaptive optics and instrumentation. The site selection has been successfully concluded and we discuss areas where the site selection impacts the design.

This paper addresses the issue of calibrating the Advanced Technology Solar Telescope for high-precision polarimetry, in particular of the optical train above the Gregorian station (where suitable calibration optics will be placed). Conventional techniques would not be adequate for this telescope given its large aperture. Here we explore two different methods that are currently being considered by the design team. The first one is the "sub-aperture" method, which uses small calibration optics above the primary mirror to calibrate a small sub-aperture of the system. This calibration is then extended to the full aperture by means of actual observations. The second method is based on analyzing the polarization observed in a spectral line with a peculiar Zeeman pattern, such as the FeII 614.9 nm line, which does not produce any intrinsic linear polarization. Numerical simulations are presented that show the robustness of both techniques and their respective advantages and disadvantages are discussed.

The mission of the ATST visible spectro-polarimeter (ViSP) is to provide precision measurements of the full state of polarization (Stokes parameters) simultaneously at diverse wavelengths in the visible spectrum and fully resolve (or nearly so) the profiles of spectrum lines originating in the solar atmosphere. We present the instrument science requirements, their flow down to instrument specifications, and a preliminary ViSP design. The ViSP spectrograph allows for reconfiguration while maintaining an immediately selectable configuration. We describe how the ViSP will utilize the ATST polarimetry facility.

The measurements of velocity and temperature of coronal electrons are of immense importance to the study of coronal dynamics, especially in the low solar corona. In this lies interesting physics yet to fully explain the theoretical reasoning for the million degree hot coronal plasma and the cause for the initial acceleration of this coronal plasma. In this regard it would be equally important if both of these coronal electron parameters, namely the velocity and the temperature of these coronal electrons, could be determined simultaneously and globally all around the low solar corona. The purpose of this paper is twin fold. First, to lay out an instrumental procedure that allows for the measurement of a coronal signature that could measure all around the low solar corona simultaneously. Second, to describe a theoretical procedure that allows for deriving both the coronal electron temperature and its bulk flow velocity from the measured coronal signature.

The telescope structure including control system and the complete retractable dome of the new 1.5 m solar telescope GREGOR were assembled during 2004 at Izana on Tenerife, Spain. The GREGOR telescope is build by a consortium of the Kiepenheuer Institut fuer Sonnenphysik, the Astrophysikalische Institut Potsdam, the Institut fuer Astrophysik Goettingen and additional national and international Partners. Pointing, tracking and thermal tests were made to verify the proposed performance. The results of these tests and a progress report of the project will be presented.

The Avalanche Photodiode X-ray Spectrometer (AXS) is an optics free spectrometer operating in the 400 eV - 10 keV energy range. The purpose of the instrument is to measure the solar full disk irradiance from .1 to 2 nm with a spectral resolution on the order of ΔE/E equal to approximately 15%. This spectral region is a key and highly variable energy source to the lower thermosphere. The instrument was developed for sounding rocket use and, in addition to the science objectives, is used for underflight calibration of National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite (GOES) X-ray instruments. Photon events from an avalanche photodiode produce electron showers that are detected by analog electronics. Pulse height analysis yields the energy of the impacting photon. By recording the number of events per pulse height bin, the AXS produces a spectrum. This instrument has been developed at the University of Alaska (UAF) and was flown on a sounding rocket on October 15, 2004. Calibrations were performed at the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF) III facility in Gaithersburg Maryland. In this paper the instrument design and calibration are discussed as well as both laboratory and rocket flight measurements.

The responsivity of a SiC photodiode was measured with synchrotron radiation in the deep UV and for the first time in the EUV and soft x-ray wavelength regions. A peak responsivity was 200 mA/W at 270 nm wavelength and 60 mA/w at 13 nm in the EUV. Extended measurements at shorter wavelengths demonstrated a responsivity up to 80 mA/W for wavelengths as short as 1.5 nm. The responsivity was calculated by an optical model that accounted for the reflection and absorption of the incident electromagnetic wave, the pair creation energy in the 6H-SiC device, and the variation of the charge collection efficiency (CCE) with depth into the device. The calculated responsivity was in excellent agreement with the measured responsivity and with the structure of the p-n junction photodiode. The measured visible light sensitivity was a factor of 100 lower than that of a silicon photodiode. These new results open up several possible applications for SiC photodiodes, including the selective detection of EUV and soft x-ray radiation without contamination by visible and IR wavelengths. SiC photodiodes have also been proven to withstand prolonged UV exposure and extreme temperatures, thus making them nearly ideal detectors for fiiture solar and space missions where absolutely calibrated EUV and soft x-ray intensities must be accurately measured.

NOAA's Geostationary Operational Environmental Satellites (GOES) monitor the solar X-ray activity that enable the NWS Space Environment Center to perform operational specification and forecast of the space environment. The disk-integrated solar X-ray flux has been recorded for more than two decades by the GOES X-ray Sensor (XRS). Since 2003, GOES Solar X-ray Imager (SXI) has provided real-time images of the Sun and lower corona. On 2004 October 15, a sounding rocket launched from White Sands Missile Range marked an important milestone in the first-ever attempt at on-orbit response calibration of GOES X-ray instrumentation. This paper provides an overview of this effort, which includes participation of NOAA, NASA, University of Alaska, and University of Colorado. In addition, results of initial data reduction and analysis for the XRS, SXI, and the sounding rocket are presented.

Modern auroral research uses a variety of optical instruments ranging from photometers to spectral imagers. We report our results in developing an inexpensive auroral imager, which captures true-colour images using four wide-band channels. While not replacing dedicated highly sensitive cameras with filter wheels and narrow bandpass filters, the advantages of capturing the colour should not be underestimated. The colour not only provides more information about the physical processes in the ionosphere but also enhances both manual and automated image processing due to the discriminating power of colour information. We have operated our auroral imager RAINBOW in Athabasca, Alberta, Canada for over a year. RAINBOW can acquire images every ten seconds and operate even in moonlit conditions. A clever design using inexpensive optical components provides a field-of-view of approximately 150 degrees, and an external shutter provides protection from direct sunlight. We discuss the issues related to imager hardware and colour calibration. Future applications are also highlighted.

Radio arrays currently operating below 1 GHz have observed interplanetary scintillations of radio sources to derive valuable information on the density and velocity of the solar wind and coronal mass ejections. New large radio arrays are currently in the design and development phase, and are characterized by wide fields of view, high sensitivity, and multiple beam capabilities. One such array, the Mileura Widefield Array - Low Frequency Demonstrator (MWA-LFD) in Western Australia, is being designed for operation at 80 to 300 MHz. Its characteristics include a 15-50^o field-of-view, 16 simultaneous beams, and an effective collecting area of 8000 m² at 200 MHz with 32 MHz instantaneous bandwidth resulting in a point-source sensitivity of 20 mJy for an integration time of one second. The array consists of 8000 dual-polarization dipoles, clustered in sub-arrays that are spread over a 1.5 km diameter and connected to a central digital signal processor. The MWA-LFD will participate in the global network of observatories that monitor solar bursts and interplanetary scintillations, and will improve the spatial and time resolution of solar wind characterization by increasing both the number of radio sources that can be used for scintillation measurements and the number of observations that can be made in a given time period. In addition, the MWA-LFD will be able to provide observations of the Faraday rotation of polarized radio sources, thus allowing the possibility of determining the evolution of the magnetic field in a coronal mass ejection. The design of the array, the signals expected to be received by the array, and the requirements and challenges for the space weather observations are discussed in this paper.

Far ultraviolet (FUV) images of Earth from space have proven invaluable in revealing contextual phenomena associated with space weather in the high latitude auroral regions and in the mid and equatorial regions. Images of this nature can be used to investigate compelling questions associated with the interaction of the ionosphere/mesosphere-magnetosphere-solar wind. Observations using images that lead to quantitative analyses are required to significantly advance the state of knowledge with regard to the affects of space weather and the interaction between and within these regions of Geospace. Current available image data sets are sufficient for qualitative analysis and morphological investigations, and while quantitative analyses are possible, they are difficult and limited to few events at best^1,2. In order to qualitatively access the time, spatial, and causal phenomena on global scales, simultaneous images of various FUV emissions with a combination of better spatial, temporal and spectral resolution and sensitivity than currently available are required. We present an instrument concept that is being developed to improve the spatial, temporal and spectral resolution and sensitivity needed to perform the quantitative analysis that enable significant advancement in our understanding of the impact of space weather on Geospace. The approach is to use the "self-filtering" concept³ that combines the imaging and filtering functions and thus reduces the size of the 4-mirror off-axis optical system. The optical and filter design will de described.

Inner heliosphere measurements of the Sun can be conducted with the proposed Solar Sentinel spacecraft and mission. One of the key measurements that can be made inside the orbit of the Earth is that of lower energy neutrons that arise in flares from nuclear reactions. Solar flare neutrons below 10 MeV suffer heavy weak-decay losses before reaching 1 AU. For heliocentric radii as close as 0.3 AU, the number of surviving neutrons from a solar event is dramatically greater. Neutrons from 1-10 MeV provide a new measure of heavy ion interactions at low energies, where the vast majority of energetic ions reside. Such measurements are difficult because of locally generated background neutrons. An instrument to make these measurements must be compact, lightweight and efficient. We describe our progress in developing a low-energy neutron telescope that can operate and measure neutrons in the inner heliosphere and take a brief look at other possible applications for this detector.

The first of five Special Sensor Ultraviolet Limb Imager (SSULI) sensors was launched on the Defense Meteorological Satellite Program (DMSP) F16 spacecraft in October of 2003 into a sun-synchronous 830 km circular orbit at a local time of 0800-2000 UT. During initial sensor turn-on and evaluation, unusually high levels of background events were observed by the detector. The severity of this background is often sufficient to exceed the counting limit of the electronics as well as contribute to a rapid decrease in detector performance. In light of the SSULI performance degradation and concerns that the subsequent sensors may be affected in a similar manner, a "Tiger Team" investigation was launched to determine the source of the anomalous events. The conclusion from the investigation attributes the observed anomalous events to high levels of non-photon noise caused by ambient ions entering the instrument and striking the front microchannel plate. Additionally, the team made recommendations to mitigate the problem on future flights.

In the extreme ultra-violet region, multilayer coatings are the only technique to obtain high reflectivity in normal incidence optical configurations. The interference process which regulates periodic multilayers behavior offers narrow-band spectral filtering without the use of additional filters, fact that makes these coatings particularly suitable for lines emission observations. Despite the large amount of possible materials combinations, Mo/Si multilayers are the standard choice for space research on plasma physics in the 13 - 30 nm spectral region. In this work Si/B₄C is presented as an alternative material couple for the 30.4 nm selection. Attractive features are the better spectral purity and the second order reflectivity reduction. A possible application to the Sounding CORonagraph Experiment is described as an example. B₄C thin films have been used to characterize this material in terms of optical constants in the 40 nm - 150 nm spectral region where, currently, only few data are available.

We present experimental results on the development and testing of the extreme ultraviolet (EUV) reflective multilayer coatings that will be used in the Atmospheric Imaging Assembly (AIA) instrument. The AIA, comprising four normal incidence telescopes, is one of three instruments aboard the Solar Dynamics Observatory mission, part of NASA's Living with a Star program, currently scheduled for launch in 2008. Seven different multilayer coatings will be used, covering the wavelength region from 93.9 to 335.4 Å.

In this paper we highlight the advances we have made in applying modern diamond-turning technology and techniques to the problem of manufacturing coarse-spaced echelon and echelle gratings for infrared spectroscopy-gratings with groove profiles and coarse line spacings that could not be produced using traditional ruling techniques. Diffraction gratings have been classified into three categories: echelons, echelettes, and echelles. What distinguishes these categories from one another are the gratings': line spacing, order of use, and the methods of manufacture. For example, echelles used in the visible and UV regions are ruled gratings, their grooves being formed to a specific "sawtooth" or blazed profile by a ruling process. In comparison echelons were not ruled gratings but an assembly of plane-parallel optical flats, stacked on one another to form a series of rectangular steps. By applying diamond-turning technology, Bach Research has been able to produce diamond-machined echelons and coarse echelles for use in far and near infrared spectroscopy. These gratings have line spacings from 7.5 to 0.25 mm and groove depths of 0.75 to 0.125 mm. These grooves are intentionally large with respect to the infrared wavelength of interest and were produced by machining directly into bulk-metal substrates. This was accomplished while maintaining the precision in spacing and "blazed" groove profile, so that the resulting grating had a diffracted wavefront quality of 0.7 waves RMS, in the 702nd order of 632.8 nm.

In order to obtain an image of the solar corona, coronagraph optical design needs to be optimized with respect to stray light reduction. Despite the accurate optical design, some stray light is present on the focal plane in addition to the coronal signal. The stray light level has to be estimated in order to test the quality of the optical design. The stray light is given by scattering off the surfaces of the optical elements and by diffraction from the instrument apertures. In order to estimate the stray light level on the focal plane, a diffraction calculation is necessary. In this paper we describe the diffraction calculation for a coronagraph with an innovative stray light reduction design. For the same optical configuration we used two different algorithms, based on different approaches to Fresnel diffraction computation. By using the Fresnel-Kirchhoff scalar theory we developed an algorithm, and we used it to write codes in IDL (Interactive Data Language, by Research System Inc.), and C programming languages. By using the GLAD (General Laser Analysis and Design, by AOR) software, which diffraction algorithm is based on the principles of Fourier optics, we wrote a further code. In this paper we compare the results of the different codes and we discuss their efficiencies.

A small, but highly variable fraction of the total solar irradiance lies in the extreme ultraviolet (EUV) spectrum. EUV radiation heats Earth's ionosphere, sometimes disrupting microwave communication and navigation and increasing the drag on satellites in low-Earth orbits. Each of the next series of Geostationary Operational Environmental Satellites (GOES), scheduled to operate from 2012 until at least 2029, will fly an EUV Sensor (EUVS) to measure the solar irradiance operationally in several EUV spectral bands. We propose a novel approach using zone plates (ZPs) instead of the transmission gratings that are now in use. A ZP can be used to form a solar image on a small detector array at a selected EUV wavelength. Since the focal length of a ZP is inversely proportional to wavelength, other wavelengths within the passband of the sensor will be blurred at the focal plane. The ZP can be mounted on a thin-film metallic substrate that can act as a filter, transmitting EUV radiation while blocking light at longer wavelengths. Another thin-film spectral filter on the front surface of the detector can further increase the spectral selectivity of the EUVS and make it less sensitive to defects in either thin film. The circular symmetry of the ZP minimizes the variation in detected signal with field angle and polarization, and its focusing capability allows the detectors to be small, making them easier to fabricate and improving their radiometric performance. ZPs are now used routinely at soft X-ray and short EUV wavelengths.

The Ionospheric Mapping and Geocoronal Experiment (IMAGER) is a space-based, multispectral, imaging payload, designed at the U.S. Naval Research Laboratory. The IMAGER's primary science mission is to find, track, and measure ionospheric irregularities as they move across the surface of the Earth and vary with time. IMAGER will observe the ionosphere of the Earth in narrow extreme- and far-ultraviolet passbands centered at 83.4, 130.4, 135.6, and 143.0 nm. These emissions are produced by naturally occurring airglow emission from the nighttime and daytime ionosphere and thermosphere. The IMAGER consists of an imaging telescope with a filter wheel assembly and a pair of microchannel plate-based imaging detectors with cross delay line readouts. The telescope of the instrument consists of a 160 mm diameter, F/4.0 off-axis very fast aplanatic Gregorian telescope. The focal length is 640 mm and the field of view is 1.6° × 1.6° which will cover approximately 1000 × 1000 km² on the Earth's surface. The modulation transfer function is above 0.90 at 2.8 line pairs-millimeter^-1 over the field, which corresponds to a line pair separated by 20 km on the Earth. The spatial resolution is approximately 10 × 10 km² and is oversampled by a factor of 9 (3 × 3 pixels per resolution element). A system of reflective filters is used to select different wavelengths of interest. The telescope will be gimbaled to provide a field-of-regard encompassing the entire disk and limb of the Earth. The gimbal will also allow the telescope to track the ionospheric irregularities as they move. This paper describes the design of the optical and mechanical systems and their intended performance and includes an overview of the mission and science requirements that defined the aforementioned systems.

This paper will describe the objectives of the Marshall Space Flight Center (MSFC) Solar Ultraviolet Magnetograph Investigation (SUMI) and the optical components that have been developed to meet those objectives. A sounding rocket payload is being developed to test the feasibility of magnetic field measurements in the Sun's transition region. The optics have been optimized for simultaneous measurements of two magnetic lines formed in the transition region (CIV at 1550Å and MgII at 2800Å). Finally, this paper will concentrate on the polarization properties of the SUMI polarimeter and toroidal variable-line-space gratings.

PROBA2 is an ESA technology demonstration mission to be launched in early 2007. The two primary scientific instruments on board of PROBA2 are SWAP (Sun Watcher using Active Pixel System detector and Image Processing) and the LYRA VUV radiometer. SWAP provides a full disk solar imaging capability with a bandpass filter centred at 17.5 nm (FeIX-XI) and a fast cadence of ≈1 min. The telescope is based on an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV) enhanced APS CMOS will be used as a detector. As the prime goal of the SWAP is solar monitoring and advance warning of Coronal Mass Ejections (CME), on-board intellige nce will be implemented. Image recognition software using experimental algorithms will be used to detect CMEs during the first phase of eruption so the event can be tracked by the spacecraft without huma n intervention. LYRA will monitor solar irradiance in four different VUV passbands with a cadence of up to 100 Hz. The four channels were chosen for their relevance to solar physics, aeronomy and space weather: 115-125 nm (Lyman-α), 200-220 nm Herzberg continuum, the 17-70 nm Aluminium filter channel (that includes the HeII line at 30.4 nm) and the 1-20 nm Zirconium filter channel. On-board calibration sources will monitor the stability of the detectors and the filters throughout the duration of the mission.

The Solar Orbiter mission is presently in assessment phase by the Science Payload and Advanced Concepts Office of the European Space Agency. The mission is confirmed in the Cosmic Vision programme, with the objective of a launch in October 2013 and no later than May 2015. The Solar Orbiter mission incorporates both a near-Sun (~0.22 AU) and a high-latitude (~ 35 deg) phase, posing new challenges in terms of protection from the intense solar radiation and related spacecraft thermal control, to remain compatible with the programmatic constraints of a medium class mission. This paper provides an overview of the assessment study activities, with specific emphasis on the definition of the model payload and its accommodation in the spacecraft. The main results of the industrial activities conducted with Alcatel Space and EADS-Astrium are summarized.

The NASA Living With a Star (LWS) Sentinels mission is presently being defined by its Science and Technology Definition Team (STDT). Sentinels is the third element of the LWS program. Its primary scientific objective is to discover, understand and model the connection between solar phenomena and the interplanetary/geospace disturbances, specifically, the heliospheric initiation, propagation and solar connection of those energetic phenomena that adversely affect space exploration and life and society here on Earth. Sentinels will play a particularly important role in support of NASA's new Vision for Space Exploration (VSE), in providing key new measurements required to understand the production of Solar Energetic Particles (SEPs) that are hazardous to human and robotic missions to the Moon and Mars. Here we describe the planning for Sentinels, and the preliminary design of the first phase, the Inner Heliosphere Sentinels, a four spacecraft mission to provide multi-point longitudinally and radially distributed in situ observations of SEPs, plasma, fields, and X-rays/gamma-rays/neutrons in the inner heliosphere (~0.25-0.76 AU), close to the site of SEP acceleration and rapid transient evolution.

A problem of fundamental importance for future space travel to the Moon and Mars is the determination and prediction of the radiation environment generated by the Sun. The sources of solar energetic particles (SEP) and the physical processes associated with their acceleration and propagation are not well understood. Ultraviolet coronagraphic spectroscopy uniquely has the capabilities for determining the detailed plasma properties of the likely source regions of such particles. This information can be used to develop empirical models of the source regions for specific events, and it can provide the key information needed to identify and understand the physical processes that produce SEP hazards. UVCS/SOHO observations have provided the first detailed diagnostics of the plasma parameters of coronal mass ejections (CMEs) in the extended corona. These observations have provided new insights into the roles of shock waves, reconnection and magnetic helicity in CME eruptions. Next generation ultraviolet coronagraph spectrometers could provide additional diagnostic capabilities. This paper summarizes past observations, and discusses the diagnostic potential of advanced ultraviolet coronagraphic spectroscopy for characterizing two possible sites of SEP production: CME shocks and reconnection current sheets.

The Magnetic Transition Region Probe is a space telescope designed to measure the magnetic field at several heights and temperatures in the solar atmosphere, providing observations spanning the chromospheric region where the field is expected to become force free. The primary goal is to provide an early warning system (hours to days) for solar energetic particle events that pose a serious hazard to astronauts in deep space and to understand the source regions of these particles. The required magnetic field data consist of simultaneous circular and linear polarization measurements in several spectral lines over the wavelength range from 150 to 855 nm. Because the observations are photon limited an optical telescope with a large (>18m²) collecting area is required. To keep the heat dissipation problem manageable we have chosen to implement MTRAP with six separate Gregorian telescopes, each with ~ 3 m² collecting area, that are brought to a common focus. The necessary large field of view (5 × 5 arcmin²) and high angular resolution (0.025 arcsec pixels) require large detector arrays and, because of the requirements on signal to noise (10³), pixels with large full well depths to reduce the readout time and improve the temporal resolution. The optical and engineering considerations that have gone into the development of a concept that meets MTRAP's requirements are described.

Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. The physics governing the dynamics of such plasmas takes place on remarkably small spatial and temporal scales, while both the cause activity and the response occur on large spatial scales. Thus both high resolution and large fields of view are needed. Observations from SMM, Yohkoh, EIT and TRACE show that typical solar active region structures range in temperature from 0.5 to 10 MK, and up to 40MK in flares, implying the need for broad temperature coverage. The RAM S-T Probe consists of a set of imaging and spectroscopic instruments that will enable definitive studies of fundamental physical processes that govern not only the solar atmosphere but much of the plasma universe. Few problems in astrophysics have proved as resistant to solution as the microphysics that results in the production of high-energy particles in hot magnetized plasmas. Theoretical models have focused in recent years on the various ways in which energy may be transported to the corona, and there dissipated, through the reconnection of magnetic fields. Theory implies that the actual dissipation of energy in the corona occurs in spatially highly localized regions, and there is observational support for unresolved structures with filling factors 0.01 - 0.001 in dynamic coronal events.

This paper describes an instrument concept for imaging spectroscopy of ultraviolet (UV) line emission from the solar corona, in the (30-120) nm wavelength range. The optical design for this Ultraviolet Spectro-Coronagraph (UVSC) instrument concept is an externally occulted, off-axis Gregorian telescope where the secondary mirror is a Toroidal Varied Line-Space (TVLS) grating. A field stop with multiple slits is at the prime focus of the telescope's mirror. This multi-slit field stop is the entrance aperture for the spectrograph. The slits select a number of strips in the field-of-view (FOV) with enough separation to minimize the spectral overlap of the UV lines dispersed by the TVLS grating. The complete two-dimensional imaging of the FOV is obtained by interpolating the slit images along the spectral dispersion direction. This paper discusses the use of an UVSC instrument on HERSCHEL, a NASA sounding-rocket payload. HERSCHEL includes the Sounding-rocket CORonal Experiment (SCORE) that currently comprises a UV Coronagraphic Imager (UVCI) for narrow-band (i.e., λ/Δλ≈10) imaging of the HeII, 30.38 nm, line. Adding a spectroscopic capability (i.e., λ/Δλ ≈ 0.3-1 × 10⁴) to the UVCI would enhance the HERSCHEL's science. This paper presents the ray-tracing results of the expected spectral and spatial performances of a UVSC/SCORE optimised for the HeII, 30.38 nm, line.

Orbiting around the Sun on an inclined orbit with a 0.2 UA perihelion, the Solar Orbiter probe will provide high resolution views of the Sun from various angles unattainable from Earth. Together with a set of high resolution imagers, the Full Sun Imager is part of the EUV Imaging suite of the Solar Orbiter mission. The mission's ambitious characteristics draw severe constraints on the design of these instruments. We present a photometrically efficient, compact, and lightweight design for the Full Sun Imager. With a 5 degrees field of view, this telescope will be able to see the global solar coronal structure from high viewing angles. Thermal solutions reducing the maximum power trapped in the High Resolution Imagers are also proposed.

Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent observing the inner corona inside typically 2-2.5 solar radii. Formation flyers open new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100 m from the first one. ASPICS (Association de Satellites Pour l'Imagerie Coronographique Solaire) is a mission proposed to CNES in the framework of their demonstration program of formation flyers which is presently under study to exploit this technique for coronal observations. In the baseline concept, ASPICS includes three coronagraphs operating in three spectral domains: the visible continuum (K-corona brightness), the HI Lyman alpha emission line at 121.6 nm, and the HeII emission line at 30.4 nm. Their unvignetted fields of view extend from 1.1 to 3.2 solar radii with a typical spatial resolution of 3 arcsec. In order to connect coronal activity to photospheric events, ASPICS further includes two disk imagers. The first one is devoted to the HI Lyman alpha emission line. The second one is a multi-channel instrument similar to SOHO/EIT and devoted to the HeII (30.4 nm), FeIX/X (17.1 nm) and FeXII (19.5 nm) emission lines. Two concepts of the space system are under consideration: a symmetric configuration where the disk imagers and the external occulter are on one spacecraft and the coronagraphs on the other, an asymmetric configuration where the external occulter is on one spacecraft and the scientific instruments are regrouped on the other one.

The recent possibility of deploying clusters of satellites in flight formation allows the development of a new generation of space instruments, and among them, of externally occulted solar coronagraphs. This can be implemented by introducing a large occulter on a first satellite, and all the remaining optical system on a second satellite, located in the shadow of the occulter. Since the capability of looking close to the solar limb is directly related to the distance between the external occulter and the coronagraphic objective, formation flyers offer the capability of a major improvement in observing the lower corona from space. In this paper, we describe a possible optical design for ASPICS, a formation flyer solar coronagraph composed of two satellites separated by about 100 m. The proposed dual channel design will allow for the first time to simultaneously observe the lower and intermediate corona in both visible and ultraviolet (HI Lyman-α line) spectral regions at a 6 arcsec/pixel scale factor with a single instrument.

The Solar Mass Ejection Imager (SMEI) was launched on 6 January 2003, and shortly thereafter raised to a nearly circular orbit at 840 km. Three SMEI CCD cameras on the zenith-nadir oriented CORIOLIS spacecraft cover most of the sky beyond about 20°. from the Sun, each 102-minute orbit. Data from this instrument provide precision visible-light photometric sky maps. Once starlight and other constant or slowly varying backgrounds are subtracted, the residue is mostly sunlight that has been Thomson-scattered from heliospheric electrons. These maps enable 3-dimensional tomographic reconstruction of heliospheric density and velocity. This analysis requires 0.1% photometry and background-light reduction below one S10 (the brightness equivalent of a 10th magnitude star per square degree). Thus 10^-15 of surface-brightness reduction is required relative to the solar disk. The SMEI labyrinthine baffle provides roughly 10^-10 of this reduction; the subsequent optics system provides the remainder. We analyze data obtained over two years in space, and evaluate the full system's stray-light rejection performance.

We present a volume rendering system developed for the real time visualization and manipulation of 3D heliospheric volumetric solar wind density and velocity data obtained from the Solar Mass Ejection Imager (SMEI) and interplanetary scintillation (IPS) velocities over the same time period. Our system exploits the capabilities of the VolumePro 1000 board from TeraRecon, Inc., a low-cost 64-bit PCI board capable of rendering up to a 512-cubed array of volume data in real time at up to 30 frames per second on a standard PC. Many volume-rendering operations have been implemented with this system such as stereo/perspective views, animations of time-sequences, and determination of coronal mass ejection (CME) volumes and masses. In these visualizations we highlight one time period where a halo CMEs was observed by SMEI to engulf Earth on October 29, 2003. We demonstrate how this system is used to measure the distribution of structure and provide 3D mass for individual CME features, including the ejecta associated with the large prominence viewed moving to the south of Earth following the late October CME. Comparisons with the IPS velocity volumetric data give pixel by pixel and total kinetic energies for these events.

The Solar Mass Ejection Imager (SMEI) records a photometric white-light response of the interplanetary medium from Earth orbit over most of the sky. We present the techniques required to process the SMEI data in near real time from the raw CCD images to their final assembly into photometrically accurate maps of the sky brightness of Thomson scattered sunlight. Steps in the SMEI data processing include: integration of new data into the SMEI data base; conditioning to remove from the raw CCD images an electronic offset (pedestal) and a temperature-dependent dark current pattern; placement ("indexing") of the CCD images onto a high-resolution sidereal grid using known spacecraft pointing information. During the indexing the bulk of high-energy-particle hits (cosmic rays), space debris inside the field of view, and pixels with a sudden state change ("flipper pixels") are identified. Once the high-resolution grid is produced, it is reformatted to a lower-resolution set of sidereal maps of sky brightness. From these we remove bright stars, background stars, and a zodiacal cloud model (their brightnesses are retained as additional data products). The final maps can be represented in any convenient sky coordinate system, e.g., Sun-centered Hammer-Aitoff or "fisheye" projections. Time series at selected sidereal locations are extracted and processed further to remove aurorae, variable stars and other unwanted signals. These time series of the heliospheric Thomson scattering brightness (with a long-term base removed) are used in 3D tomographic reconstructions.

Recent possibility of building clusters of micro-satellites have increased the interest on extremely large space instruments. Since this growing is not merely a change of scale, performance of these new instruments has to be critically re-analyzed under this new perspective. As an example, diffraction effects can lead to new levels of signal-to-noise ratio, greatly increasing the possible performance of classical optical instruments. In this work we have analyzed the diffraction behavior of an opaque disc acting as external occulter in a space solar coronagraph. Since the occulter can be set at great distance from the telescope, improvements on signal-to-noise ratio are obtained. Moreover, this analysis can lead to a determination of a potential apodization function for the occulter.

Variability in the solar UV and EUV irradiance is an important driver of the temperature of the Earth's upper atmosphere. The variation of the Magnesium II emission at 280 nm is a useful proxy for the variation at shorter wavelengths. Currently, the emission by the Mg II lines is measured only a few times per day at best, and often only a single measurement per day is available. An instrument dedicated to measuring only the Magnesium II solar output on a high time cadence will greatly improve our knowledge of the energy input to the atmosphere. Such an instrument would have very modest power, size, and weight requirements, and could easily be one component of a suite of solar instruments on a future space mission. We present some design options for a lightweight solar Magnesium II monitor that would provide measurements suitable for space weather studies.

The space-born coronagraph is an instrument used to observe the solar corona, the outer atmosphere of the Sun, typically over a range of altitudes from close to the limb of the solar disk to tens of solar radii. The brightness of the solar disk is many orders of magnitude greater than that of the corona. A coronagraph is designed to reject the light from the solar disk such that the corona is observable. An externally-occulted coronagraph is basically a telescope that forms an image of the corona, with the addition of an external occulter before and an internal occulter after the objective elements and stops, positioned and sized to reject light from the solar disk. The main source of stray light is diffraction of solar light around the edge of the external occulter, which is then scattered into the image plane by the optical elements. The occulters and stops are designed to reduce the intensity of diffracted and scattered light in the coronagraph as much as possible. We have developed a numerical model of the diffraction by an external occulter system and validated the model experimentally. We used the model to optimize the external occulter design for the SECCHI COR2 instrument, which is part of the NASA STEREO mission. We also used the model for the GOES-R SCOR concept design to predict the sensitivity of the instrument to misalignment and off-pointing from the Sun. In this paper, we will present the results of this experimental and numerical study of the performance of the external occulters on these instruments.

The spectral line of HeI 1083nm is important and potential to measure the magnetic field of the solar upper chromosphere. In this paper, we present a newly developed Stokes polarimeter for measuring the polarized signals at this wavelength. In this device, two Liquid Crystal Variable Retarders (LCVRs) were employed as electro-optical modulators and a Wollaston prism as analyzer and polarized beam splitter. Compared to the commonly used linear-polarized analyzer, the Wollaston prism analyzer has main advantage to minimize the seeing-induced contamination of earth's atmosphere, as it produces simultaneous images by the two perpendicular polarization states. A novel optical design which focuses the two beams on different detector areas is described. And the accurate calibration methods are introduced too.

We describe the design and first calibration tests of an imaging polarimeter based on Liquid Crystal Variable Retarders (LCVRs), for the study of the solar K-corona. This K-polarimeter (KPol) is part of the visible light path of the UltraViolet and Visible-light Coronal Imager (UVCI) of the Sounding-rocket Coronagraphic Experiment (SCORE). SCORE/UVCI is an externally occulted, off-axis Gregorian telescope, optimized for the narrow-band (i.e., λ/▵λ ~10) imaging of the HeII, λ 30.4 nm and HI λ 121.6 nm coronal emission. We present some preliminary results of the application of LCVR plates to measurements of linear polarized radiation. LCVR plates replace mechanically rotating retarders with electro-optical devices, without no moving parts. LCVR are variable waveplates, in which the change of the retardance is induced by a variable applied voltage. The retardance of a LCVR is a function of the wavelength. KPol observations of the visible coronal continuum of the Sun (K-corona) will be made over the 450-600 nm wavelength band. We have studied the LCVR's properties in this bandpass. We tested a LCVR plate assembled in a linear polarization rotator configuration to measure the polarization plane rotation of input radiation as a function of wavelength. We estimated the LCVR's chromatic response in the KPol wavelength bandpass. The preliminary results show reasonable achromatic behaviour at high regimes of the driving voltage, V_d (i.e., V_d>3 volt).

Rapid progress in the AlGaN (E_g=3.4-6.2eV), 4H-SiC (E_g=3.2eV) and ZnMgO (E_g=2.8-7.9eV) material systems over the last five years has led to the demonstration of a number of opto-electronic devices. These wide energy band gap devices offer several key advantages for space applications, over conventional Si (E_g=1.1eV) based devices, such as visible-blind detection, high thermal stability, better radiation hardness, high breakdown electric field, high chemical inertness and greater mechanical strength. Furthermore, the shorter cut-off wavelength of these material systems eliminates the need for bulky and expensive optical filtering components mitigating risk and allowing for simpler optical design of instrumentation. In this paper, we report on the development at NASA/Goddard of ultra-sensitive, high quantum efficiency AlGaN and 4H-SiC Schottky barrier UV-EUV photodiodes, 4H-SiC UV single photon avalanche diodes, large format 256x256 AlGaN UV p-i-n photodiode arrays and recent progress in elemental substitution for p-type and enhanced n-type doping of ZnO.