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The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) is a five telescope package, which has been developed for the Solar Terrestrial Relation Observatory (STEREO) mission by the Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics Laboratory (USA), the Goddard Space Flight Center (USA), the University of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the Max Planck Institute for Solar System Research (Germany), the Centre Spatiale de Leige (Belgium), the Institut d'Optique (France) and the Institut d'Astrophysique Spatiale (France). SECCHI comprises five telescopes, which together image the solar corona from the solar disk to beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI: 1-1.7 R ), two traditional Lyot coronagraphs (COR1: 1.5-4 R and COR2: 2.5-15 R ) and two new designs of heliospheric imagers (HI-1: 15-84 R and HI-2: 66-318 R ). All the instruments use 2048 × 2048 pixel CCD arrays in a backside-in mode. The EUVI backside surface has been specially processed for EUV sensitivity, while the others have an anti-reflection coating applied. A multi-tasking operating system, running on a PowerPC CPU, receives commands from the spacecraft, controls the instrument operations, acquires the images and compresses them for downlink through the main science channel (at compression factors typically up to 20×) and also through a low bandwidth channel to be used for space weather forecasting (at compression factors up to 200×). An image compression factor of about 10× enable the collection of images at the rate of about one every 2-3 minutes. Identical instruments, except for different sizes of occulters, are included on the STEREO-A and STEREO-B spacecraft.

Solar Probe Plus (SPP) will be the first spacecraft to fly into the low solar corona. SPP's main science goal is to determine the structure and dynamics of the Sun's coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Understanding these fundamental phenomena has been a top-priority science goal for over five decades, dating back to the 1958 Simpson Committee Report. The scale and concept of such a mission has been revised at intervals since that time, yet the core has always been a close encounter with the Sun. The mission design and the technology and engineering developments enable SPP to meet its science objectives to: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles. The SPP mission was confirmed in March 2014 and is under development as a part of NASA's Living with a Star (LWS) Program. SPP is scheduled for launch in mid-2018, and will perform 24 orbits over a 7-year nominal mission duration. Seven Venus gravity assists gradually reduce SPP's perihelion from 35 solar radii (R S ) for the first orbit to <10 R S for the final three orbits. In this paper we present the science, B N.J. Fox

We describe a forward modeling method developed to study the coronal mass ejections observed with STEREO/SECCHI. We present a survey of 26 CMEs modeled with this method. We selected most of the bright events observed since November 2007 to August 2008, after when the separation was greater than 40°degrees, thus showing noticeable differences between the two views. From these stereoscopic observations and using a geometric model of a flux rope, we are able to determine the three-dimensional direction of propagation, the three-dimensional velocity and acceleration of the CME front, and in most of the cases the flux rope orientation and length. We define a merit function that allows us to partially automate the fit, as well as perform a sensitivity analysis on the model parameters. We find a precision on the longitude and latitude to be of a maximum of ±17°a nd ±4°, respectively, for a 10% decrease of the merit function but a precision on the flux rope orientation and length to be almost one order of magnitude larger, showing that these parameters are more difficult to estimate using only coronagraph data. Finally, comparison with independent measurements shows a good agreement with the direction and speed we estimated.

[1] The Solar and Heliospheric Observatory (SOHO) mission's white light coronagraphs have observed nearly 7000 coronal mass ejections (CMEs) between 1996 and 2002. We have documented the measured properties of all these CMEs in an online catalog. We describe this catalog and present a summary of the statistical properties of the CMEs. The primary measurements made on each CME are the apparent central position angle, the angular width in the sky plane, and the height (heliocentric distance) as a function of time. The height-time measurements are then fitted to first-and second-order polynomials to derive the average apparent speed and acceleration of the CMEs. The statistical properties of CMEs are (1) the average width of normal CMEs (20°< width 120°) increased from 47°(1996; solar minimum) to 61°(1999; early phase of solar maximum) and then decreased to 53°(2002; late phase of solar maximum), (2) CMEs were detected around the equatorial region during solar minimum, while during solar maximum CMEs appear at all latitudes, (3) the average apparent speed of CMEs increases from 300 km s À1 (solar minimum) to 500 km s À1 (solar maximum), (4) the average apparent speed of halo CMEs (957 km s À1) is twice of that of normal CMEs (428 km s À1 ), and (5) most of the slow CMEs (V 250 km s À1 ) show acceleration while most of the fast CMEs (V > 900 km s À1 ) show deceleration. Solar cycle variation and statistical properties of CMEs are revealed with greater clarity in this study as compared with previous studies. Implications of our findings for CME models are discussed.

The temporal relationship between coronal mass ejections (CMEs) and associated solar Ñares is of great importance to understanding the origin of CMEs, but it has been difficult to study owing to the nature of CME detection. In this paper, we investigate this issue using the Large Angle and Spectrometric Coronagraph and the EUV Imaging Telescope observations combined with GOES soft X-ray observations. We present four well-observed events whose source regions are close to the limb such that we are able to directly measure the CMEsÏ initial evolution in the low corona (D1È3 without any R _) extrapolation ; this height range was not available in previous space-based coronagraph observations. The velocity-time proÐles show that kinematic evolution of three of the four CMEs can be described in a three-phase scenario : the initiation phase, impulsive acceleration phase, and propagation phase. The initiation phase is characterized by a slow ascension with a speed less than 80 km s~1 for a period of tens of minutes. The initiation phase always occurs before the onset of the associated Ñare. Following the initiation phase, the CMEs display an impulsive acceleration phase that coincides very well with the ÑaresÏ rise phase lasting for a few to tens of minutes. The acceleration of CMEs ceases near the peak time of the soft X-ray Ñares. The CMEs then undergo a propagation phase, which is characterized by a constant speed or slowly decreasing in speed. The acceleration rates in the impulsive acceleration phase are in the range of 100È500 m s~2. One CME (on 1997 November 6, associated with an X9.4 Ñare) does not show an initiation phase. It has an extremely large acceleration rate of 7300 m s~2. The possible causes of CME initiation and acceleration in connection with Ñares are explored.

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