Rapid Acquisition Imaging Spectrograph (RAISE) Renewal Proposal Project

<p> The optical design of RAISE is based on a new class of UV/EUV imaging spectrometers that use  only two reflections to provide quasi-stigmatic performance simultaneously over multiple wavelengths  and spatial fields. Figure 5 summarizes the RAISE instrument design, showing photographs of each of  the components or subsystems. The design uses an off-axis parabolic telescope mirror to form a real  image of the sun on the spectrometer entrance aperture. A slit then selects a portion of the solar image,  passing its light onto a near-normal incidence toroidal grating, which re-images the spectrally dispersed  radiation onto two array detectors. Two full spectral passbands over the same one-dimensional spatial  field are recorded simultaneously with no scanning of the detectors or grating. The two different spectral  bands (1st-order 1205-1243Å and 1526-1564Å) are imaged onto two intensified Active Pixel Sensor  (APS) detectors whose focal planes are individually adjusted for optimized performance. The telescope  and grating are coated with B4C to enhance short wavelength (2nd order) reflectance (Fig. 6), enabling the  instrument to record the brightest lines between 602-622Å and 761-780Å at the same time. Table 1  summarizes the main optical parameters for RAISE.   </p> <p> <strong>TVLS Grating. </strong>The single toroidal variable line space (TVLS) grating has a toroidal surface  (Sagittal Radius = 640.5 mm, Tangential Radius = 635.3 mm), with varied line space (VLS) rulings of the  type developed originally for spherical substrates by Kita, Harada, and collaborators (1983, 1995). By  combining this VLS concept with toroidal surfaces, RAISE is the first to exploit this new class of  spectrometers, as described by Thomas (2003). For RAISE, the grating is placed 400 mm behind the slit,  with focus at a distance of approximately 1700 mm, for a spectrometer magnification of 4.25. By  operating at high magnification, the RAISE spectrometer most effectively utilizes the full length and  width available in the sounding rocket payload. The first RAISE grating, mechanically ruled by Bach  Research, Inc., was delivered in August 2007 and tested for figure, ruling density and total grating  efficiency. </p> <p> <strong>Intensified APS Cameras</strong>. The RAISE Intensified APS camera systems are 1k x 1k CMOS Active  Pixel Sensors using miniature digital camera electronics and fed by an MCP intensifier. APS cameras  were chosen for RAISE (rather than CCDs) because of their extremely fast readout, direct digital output,  low mass, low power, deep full well and high radiation tolerance. The RAISE cameras were developed at  DLR (Germany) using a Cypress/Filfactory Star 1000 APS and include a 12-bit external ADC and USB  2.0 interface. We will operate the cameras at 5-10 frames/sec readout, making dark current negligible  compared to the incoming signal. The complete camera electronics including its controller is integrated  on only one printed circuit board, and uses a rigid-flex 3D-interconnection between the boards to form a  lightweight, compact sensor head. Flight detectors were delivered by DLR in August 2008. </p> <p> <strong><em>RAISE Chromospheric Slit Jaw Camera (SJC)  </em></strong>To co-align the RAISE spectra with observations from SDO, HINODE, and IRIS, and to collect  chromospheric disk images in C IV and the continuum between 1500-1700 Å, the solar image at the  telescope focal plane (spectrograph entrance slit plane) is re-imaged onto a SJC mounted on the bo

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