HST/COS will be observing U Gem 2013 January 30 as part of Dr. Michael Shia's study of this dwarf nova. Please see AAVSO Special Notice #328 [1] for details.
Good observing!
Elizabeth Waagen, AAVSO HQ
Links:
[1] http://www.aavso.org/aavso-special-notice-328
[2] http://www.aavso.org/forums/variable-star-observing/campaigns-observation-reports