こう高度 こうど放電 ほうでん発光 はっこうでしょう
kō kōdohōdenhakkōdeshō

Noun
Desu Copula

Expresses probability in a polite manner ("probably…") of 高高度放電発光

1. Probably high-altitude discharge luminescence.

Polite
Presumptive
Conjecture