Comparison of the Low-Cost Sun Sensors of the SOURCE and EIVE CubeSats

Sun sensors are commonly used attitude determination equipment which measure a spacecraft’s attitude relative to the sun. Multiple types of low-cost sun sensors were developed for the SOURCE and EIVE CubeSats. The SOURCE sun sensors consist of single photodiodes which are placed in a one-sensor-per-face as well as a pyramid arrangement. EIVE employs digital vector sun sensors based on quad-pin photodiodes. The SOURCE sun sensors in the one-sensor-per-face arrangement archive an accuracy of \u3c10° while the pyramid arrangement accomplishes an accuracy of \u3c7.5° without and \u3c5° with calibration. EIVE’s vector sun sensors offer an raw accuracy of 3°±5°. Multiple calibration approaches are presented with the best results leading to an accuracy of 0.7±3°. A direct comparison between the SOURCE and EIVE sensor types and configurations can be drawn since the same test bench was used to measure all sensors. The objective of this paper is to present and compare the different sun sensor concepts and their results

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements