The Miniature X-ray Solar Spectrometer (MinXSS) 3U CubeSat was launched to the International Space Station (ISS) on 2015 December 6. Its deployment from the ISS is scheduled for 2016 March. MinXSS was designed and developed at the University of Colorado Boulder through a graduate project class, with significant professional support from the Laboratory for Atmospheric and Space Physics (LASP). The 3- axis attitude determination and control system (ADCS) is the Blue Canyon Technologies (BCT) XACT. This is the first flight of the XACT unit, which is the most capable commercially available 3-axis ADCS for CubeSats on the market today.
MinXSS is a science mission funded by NASA\u27s Heliophysics division and is the first CubeSat to be flown from NASA Science Mission Directorate\u27s new CubeSat Implementation Panel. The primary objective for the MinXSS mission is to better understand the energy distribution of solar soft x-ray (SXR) emissions and their impact on earth\u27s ionosphere, thermosphere, and mesosphere (ITM). MinXSS observes the solar SXR spectrum between 0.5 to 30 keV with an energy resolution of 0.15 keV full width half maximum at 5.9 keV. Very few prior spectrally-resolved solar observations exist in the SXR range, leaving a critical gap in our ability to determine the spectral energy distribution for ITM modeling and solar flare studies. These issues can be addressed with new MinXSS data.
This paper will provide details of the on-orbit performance of MinXSS and first-light observations from the primary science instrument, which is a commercially available system that was modified for flight.
First light observations will include the first solar SXR spectrum from MinXSS and comparisons between quiet-Sun and flare spectra as observed by MinXSS.
MinXSS represents the first opportunity for on-orbit characterization of BCT\u27s XACT ADCS. Performance of star tracker-based attitude determination, 3-axis reaction wheel-based attitude control, and torque rod-based momentum control will be assessed using on-orbit telemetry. This system is being used by several NASA centers, the DoD, many universities, and commercial entities for a multitude of upcoming missions that require precision attitude control at low cost.
The exceptionally simple design of the LASP PPPT will be reviewed. The addition of a single fixed-value resistor mitigates the high current draw from the battery, which prevents the solar cell voltage from dropping below buck converter input requirements. The PPPT was successful in increasing the power output of the electrical power system by nearly a factor of 2 in mission simulations. The on-orbit power performance will be analyzed.
In addition to thermal vacuum testing, MinXSS underwent thermal balance, which is dedicated to tuning the thermal model. The thermal balance procedure and model will be briefly overviewed and predictions compared to on-orbit temperatures. The results of this analysis have been generalized such that other CubeSat programs, who may not have the means to perform the test, may apply the results to their models and get improved model predictions. Thermal control of CubeSats is important to their lifetime and few if any prior results on this topic have been previously presented
