Solar B EIS Telescope Uses NRL Optics for Small-Scale Observations of Solar Atmosphere

11/27/2006 - 61-06r
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A multinational team of scientists, including members of the Naval Research Laboratory's Space Science Division, have collaborated on the Solar B satellite, a three-year mission to study the outer atmosphere of the Sun, the corona, and how it interacts with the Sun's magnetic field. Through their investigations, the scientists hope to learn the early warning signs of solar flares. While scientists understand the processes that produce solar flares, they are not yet able to predict when solar flares will occur. Accurate prediction of these events is important as energy bursts from solar flares can affect communications on Earth and space weather.

Solar B, which successfully launched on September 22 from Japan, is the follow-on mission to Yohkoh, a cooperative Japan/US/UK mission that was launched in 1991 and observed energetic activity in the solar atmosphere continuously for more than nine years. Solar B is the second of NASA's Solar Terrestrial Probes to address fundamental questions about the physics of space plasmas and flow of mass and energy through the solar system. It will perform coordinated, simultaneous measurements of the different layers of the solar atmosphere from a Sun-synchronous orbit around the Earth. Traveling in this orbit will allow Solar B to observe the Sun without interruption for nine months of the year. Similar to Yohkoh (Solar A), once launched the Solar B mission was renamed Hinode, which means "Sunrise" in Japanese.

Solar B, which is managed by the NASA Marshall Spaceflight Center, carries three instrument packages, the Solar Optical Telescope, a white-light telescope and vector magnetograph; a soft X-ray telescope; and an Extreme-ultraviolet Imaging Spectrograph (EIS). EIS is a joint Japan-UK-US instrument. The UK's Mullard Space Science Observatory leads the EIS team. NRL and the NASA Goddard Spaceflight Center provided the optics and associated mechanisms for EIS.

EIS will measure the dynamical behavior of the Suns' atmosphere more accurately than ever before, observing even the smallest changes that occur during the critical build-up to a solar flare. EIS combines, for the first time, high spectral, spatial and temporal resolution in a satellite-based, solar extreme ultraviolet (EUV) instrument. It will obtain monochromatic images of the solar corona and transition region to provide data that will be used to determine velocity fields and other plasma characteristics in the solar corona and transition region. This data will thus help relate coronal dynamic behavior to the magnetic field in the Sun's outer layer.

The EIS telescope is an off-axis paraboloid telescope with a focal length of 1.9 meters and a mirror diameter of 150 millimeters. EIS's total length is over three meters. The telescope's special multilayer coatings are highly reflective in two wavelength ranges (170 - 210 Å) and (250 - 290 Å), where many EUV emission lines from the transition region, the corona, and flares are found. The telescope feeds light into a high-resolution spectrometer and spectrally pure images from these wavelength ranges will be simultaneously observed with two large back-illuminated image sensors (charge-coupled devices, or CCDs).

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