A US mission to investigate the ionosphere involving twin identical microsatellites (‘Yahtzee’ and ‘Farkle’), each measuring 10 × 10 × 15 cm and weighing 2 kg, that were launched from California in October 2011.

https://www.astraspace.net/news/astra-dice-cubesat-update-successfully-captures-first-ever-sed-observations-by-a-cubesat/ ASTRA mission update.