The CubeSat Imaging X-ray Solar Spectrometer (CubIXSS) is a 6U CubeSat proposed to NASA H-FORT. 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 temperature range 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 for spectroscopy of flares and active regions from 1 to 55 Å, with spectral and spatial resolutions of 0.28-0.37 Å and 29-39 arcsec FWHM, respectively; and
SASS, a suite of four spatially-integrated off-the-shelf spectrometers for high-cadence, high-sensitivity X-ray spectra from 0.5 to 50 keV, with spectral resolution of 0.06-0.5 keV FWHM across that range.
If selected for implementation, CubIXSS will launch in late 2023 to mid-2024 to observe intense solar flares and active regions during the rising phase and peak of the solar cycle. Its 1-year prime 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 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.