"One year after the disaster - 'Towards Tomorrow' Concert"
It will be broadcast on NHK BS Premium from 16:00 - 22:00 (with a short break - I assume for news, from 18:45 - 19:00). And I assume a summary-show will be shown on the normal NHK channel from 19:30 - 20:45.
The main MC of the concert will be Nakai Masahiro (SMAP) and acts include: SMAP, AKB48, SKE48, Perfume, Rake, Kis-My-Ft2 and more (to be announced, around 10 acts).
Sources: NHK, Kis-My-Ft2 Official AVEX Profile