INTRODUCTION: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument investigates energetics of the solar corona and acceleration of the solar wind using high-resolution EUV spectroscopy of unprecedented sensitivity. Rapid cadence (1 s) is enabled by the instrument's high throughput (effective area more than 100 times greater than its SERTS predecessor) and the use of high-speed Active Pixel Sensors. Its two co-aligned multilayer telescope/spectrographs cover spectral ranges 30.0-37.0 nm and 52.4-63.0 nm with 2-arcsec slits that cover lengths of 11 arcmin, nearly a full solar radius. The instrument was used to verify the EIS radiometric calibration during its last flight in 2007 (Wang et al. 2011, ApJS 197, 32) and will again be radiometrically calibrated such that a similar verification can be performed with data from the flight in August 2012.
SCIENCE OBJECTIVES: EUNIS is presently scheduled to launch in the week beginning September, 24th, 2012, with a launch time likely around 17:00 UT - 17:30 UT. Our primary science objective is to investigate rapid solar variability in active region(s) and quiet areas. This will be achieved with a sequence of fast EUNIS rasters in which the slit pointings will scan back and forth continuously within maximum displacements of 20-30 arcsec to either side of the initial slit pointing. The coordinated EUNIS and EIS observations will provide extensive spectral (17.0-20.5, 25.0-29.0, 30.0-37.0, and 52.4-63.0 nm) and very wide temperature (0.1-20 MK) coverage. A secondary science objective is to cross calibrate with EIS on Hinode. This will be achieved indirectly for both EIS wavebands (17.0-20.5 nm and 25.0-29.0 nm) by comparing density- and temperature-insensitive line intensity ratios with theoretical values derived from CHIANTI. The key to the "indirect" cross calibration is that each line pair will include one member from EIS and one member from EUNIS. |
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