!# $u$ filter from Thuan & Gunn (1976), PASP 88, 543.
"u"
"energy"       
"TG"
 3100.   0.000
 3150.   0.071
 3200.   0.129
 3250.   0.307
 3300.   0.486
 3350.   0.671
 3400.   0.857
 3450.   0.929
 3500.   1.000
 3550.   0.964
 3600.   0.929
 3650.   0.786
 3700.   0.643
 3750.   0.393
 3800.   0.143
 3850.   0.071
 3900.   0.000
