The ISAS/JAXA Solar-B mission includes an Extreme-UV Imaging Spectrometer (EIS). It detects
photons in the wavelength ranges 17 - 21 nm and 25 - 29 nm which include emission lines from several
highly ionised species that exist at temperatures log T = 4.7, 5.6, 5.8, 5.9 and 6.0 - 7.3 K. Instrument
throughput is increased substantially by the use of multilayer coatings optimized for maximum
reflectance in the two selected wavelength bands. The use of back-illuminated CCDs provides
significantly enhanced quantum efficiency over that previously available from microchannel plate
systems. In this paper we will describe the design and operation of the instrument and present its
performance parameters e.g. spectral and spatial resolution and sensitivity. Preliminary results of recent
calibration measurements will be described. The role of EIS in the Solar-B mission will be illustrated
with reference to the anticipated observing strategy for the first three months of the mission which will be
<i>EUVE</i> and the <i>ROSAT WFC</i> have left a tremendous legacy in astrophysics at EUV wavelengths. More recently, <i>Chandra</i> and <i>XMM-Newton</i> have demonstrated at X-ray wavelengths the power of high-resolution astronomical spectroscopy, which allows the identification of weak emission lines, the measurement of Doppler shifts and line profiles, and the detection of narrow absorption features. This leads to a thorough understanding of the density, temperature, abundance, magnetic, and dynamic structure of astrophysical plasmas. However, the termination of the <i>EUVE</i> mission has left a gap in spectral coverage at crucial EUV wavelengths (~100-300 Å), where hot (10<sup>5</sup> - 10<sup>8</sup> K) plasmas radiate most strongly and produce critical spectral diagnostics. <i>CHIPS</i> will fill this hole only partially as it is optimized for diffuse emission and has only moderate resolution (R~150). For discrete sources, we have successfully flown a follow-on instrument to the EUVE spectrometer (A<sub>eff</sub> ~ 1 cm<sup>2</sup>, R ~ 400), the high-resolution spectrometer <i>J-PEX</i> (A<sub>eff</sub> ~ 3 cm<sup>2</sup>, R ~ 3000). Here we build on the <i>J-PEX</i> prototype and present a strawman design for an orbiting spectroscopic observatory, <i>APEX</i>, a SMEX-class instrument containing a suite of 8 spectrometers that together achieve both high effective area (A<sub>eff</sub> > 10 cm<sup>2</sup>) and high spectral resolution (R ~ 10,000) over the range 100-300 Å. We also discuss alternate configurations for shorter and longer wavelengths.
We report on the successful sounding rocket flight of the high resolution (R=3000-4000) J-PEX EUV spectrometer. J-PEX is a novel normal incidence instrument, which combines the focusing and dispersive elements of the spectrometer into a single optical element, a multilayer-coated grating. The high spectral resolution achieved has had to be matched by unprecedented high spatial resolution in the imaging microchannel plate detector used to record the data. We illustrate the performance of the complete instrument through an analysis of the 220-245Å spectrum of the white dwarf G191-B2B obtained with a 300 second exposure. The high resolution allows us to detect a low-density ionized helium component along the line of sight to the star and individual absorption lines from heavier elements in the photosphere.
The Extreme-ultraviolet Imaging Spectrometer combines, for the first time, high spectral, spatial and temporal resolution in a satellite based, solar extreme ultraviolet instrument. The instrument optical design consists of a multilayer-coated off- axis paraboloid mirror telescope followed by a toroidal grating spectrometer. The instrument includes thin film aluminum filters to reject longer wavelength solar radiation and employs CCD detectors at the focal plane. The telescope mirror is articulated to allow sampling of a large fraction of the solar surface from a single spacecraft pointing position. Monochromatic images are obtained either by rastering the solar image across the narrow entrance slit or by using a wide slit or slot in place of the slit. Monochromatic images of the region centered on the slot are obtained in a single exposure. Half of each optic is coated to maximize reflectance at 195 angstrom; the other half is coated to maximize reflectance at 270 angstrom. The two EUV wavelength bands were selected to optimize spectroscopic plasma diagnostic capabilities. Particular care was taken to choose wavelength ranges with relatively bright emission lines to obtain precision line of sight and turbulent bulk plasma velocity measurements from observed line profiles. The EIS spectral range contains emission lines formed over a temperature range from approximately 10<SUP>5</SUP> - 10<SUP>7</SUP> K. The wavelength coverage also includes several density sensitive emission line pairs. These line pairs provide spatial resolution independent density diagnostics at nominal coronal temperatures and densities. Each wavelength band is imaged onto a separate CCD detector. The main EIS instrument characteristics are: wavelength bands -- 180 - 204 angstrom and 250 - 290 angstrom; spectral resolution -- 0.0223 angstrom/pixel (23 - 34 km/second-pixel); slit dimensions -- 4 slits: 1 X 1024 arc- seconds and 50 X 1024 arc-seconds with two positions unspecified as of this writing; fine raster range -- >6 arc-minutes on the sun; coarse raster range -- > 1600 arc- seconds on the sun; largest spatial field of view in a single exposure -- 50 X 1024 arc-seconds; nominal time resolution for active region velocity studies -- 3.4s. The Solar-B satellite is scheduled for launch in August 2005 into a nominal 600 km sun-synchronous orbit.
The coronal diagnostic spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 15.0 - 80.0 nm. By observing the intensities of selected lines and line profiles, it is possible to derive temperature, density, flow, and abundance information for the plasmas in the solar atmosphere. Spatial resolution down to a few arcseconds and temporal resolution of seconds, allows such studies to be made within the fine-scale structure of the solar corona. Furthermore, coverage of a large wavelength band provides the capability for simultaneously observing the properties of plasma across the wide temperature ranges of the solar atmosphere. The CDS design makes use of a Wolter-Schwarzschild II telescope which simultaneously illuminates two spectrometer systems, one operating in normal incidence the other in grazing incidence. In this paper we describe the salient features of the design of the CDS instrument and discuss the performance characteristics of CDS as established through pre-delivery test and calibration activities.