KEYWORDS: Spectroscopy, Hard x-rays, Particles, Time metrology, Space operations, Solar radiation models, Solar processes, Silicon, Sensors, Scintillators
In the past two decades, great advances have been made in investigating hard X-rays from accelerated electrons in solar flares. This emission is of interest because the means by which flares so efficiently accelerate particles are still not understood. Observations from the RHESSI spacecraft led to better understanding in the imaging and spectral domains, but presented difficulty for time domain analysis at scales less than ~2 seconds. This leaves the behavior of flare emission at small timescales poorly explored. The NSF-funded IMpulsive Phase Rapid Energetic Solar Spectrometer (IMPRESS) CubeSat is designed specifically to measure hard X-ray emission up to 100 keV from flares at a tens-of-ms cadence. This will provide novel constraints for flare particle acceleration models. IMPRESS is a student-centered collaboration between UMN, MSU, SwRI, and UCSC. This presentation will describe the science, mission concept, and some design specifics for IMPRESS.
The EUV Snapshot Imaging Spectrograph (ESIS) is a slitless, tomographic imaging spectrograph for observing the solar transition region in extreme ultraviolet (EUV) at 63nm wavelength. An array of concave diffraction gratings re-image from the telescope prime focus to our CCD detectors. The instrument is aligned and focused in visible light, using substitute diffraction gratings ruled for the red HeNe laser line. To transfer precise alignment and focus of the visible gratings to the EUV gratings, we have developed a minitaturized, three point, noncontact measurement system, TEA (Transfer ESIS Alignment). TEA locates the grating surface using confocal microscopy, with three independent channels scanned together on a single stage, to specify the position and orientation of the spherical surface. Challenges for this measurement include the small size of the ESIS gratings (~ 16X20μm), their curved surfaces, diffraction effects, the alignment of tiny optics within TEA, and the mechanics used to repeatability mount the gratings. Our testing shows that the intrinsic repeatability of our measurement apparatus is approximately 2μm. In practice, however, our error is dominated by the process of mounting the grating subsystem in TEA, which introduces 12μm differences between subsequent runs. This level of repeatability meets our requirements for ESIS.
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