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