The CubeSat Imaging X-ray Solar Spectrometer (CubIXSS)

The CubeSat Imaging X-ray Solar Spectrometer (CubIXSS) is a 6U CubeSat currently in a formulation phase under the 2019 NASA H-FORT program. CubIXSS is motivated by a compelling overarching science question: what are the origins of hot plasma in solar flares and active regions? Elemental abundances are a unique diagnostic of how mass and energy flow into and within the corona, and CubIXSS addresses its science question through sensitive, precise measurements of abundances of key trace ion species, whose spectral signatures reveal the chromospheric or coronal origins of heated plasma across the entire range of coronal temperatures, from ~1 to >30 MK. CubIXSS measurements of the coronal temperature distribution and elemental abundances directly address longstanding inconsistencies from prior studies using instruments with limited, differing temperature and composition sensitivities.

CubIXSS comprises two co-optimized and cross-calibrated instruments that fill a critical observational gap:

MOXSI, a novel diffractive spectral imager using a pinhole camera and X-ray transmission diffraction grating to achieve spectroscopy of flares and active regions from 1 to 55 Å, with spectral resolution of 0.24 Å FWHM and a spatial resolution of 25 arcsec FWHM; and

SASS, a suite of four spatially-integrated off-the-shelf spectrometers for high-cadence, high-sensitivity measurements of soft and hard X-rays, from 0.5 to 50 keV, with spectral resolution from 0.06 to 0.5 keV FWHM.

If selected for implementation, CubIXSS will launch in mid-2023 to observe intense solar flares and active regions during the rising phase of the solar cycle. Its nominal 1-year mission is well timed with perihelia of Parker Solar Probe and Solar Orbiter, and with the launches of complementary missions such as the PUNCH Small Explorer. CubIXSS is also a pathfinder for the next generation of Explorer-class missions with improved capabilities for SXR imaging spectroscopy. We present the CubIXSS motivating science background, its suite of instruments and expected performances, and other highlights from the completed Concept Study Report, including novel analysis techniques to fully exploit the rich data set of CubIXSS spectral observations.