Haruka: Iizuka Haruko
Miki: Megumi Kouno
Iori: Ryouji Masuyama
Yukiho: Isao Hayashi
Makoto: Atsushi Nishigori
Yayoi: Satoshi Yamaguchi
Ritsuko & Producer: Tomomi Kawatsuma
Ami: Jun Uemura
Mami: Yuusuke Matsuo
Takane: Yuuki Itou
Hibiki: Yuusuke Tanaka
Kotori: Toshifumi Akai
Nonowa: Takahashi Masanori
Jupiter: Miyuki Kuroki

Can't tell who drew Chihaya and Azusa because there's either no name or it's too small to read.

Azusa is probably Noriko Takao (why would she not be featured?), but I dunno about Chihaya. Takahiro Harada maybe?

thanks to this blog post about welcome to the space show having a stupidly similar signature, im fairly certain the little chibi haruka and chihaya plank on the very bottom right are drawn by koji masunari. the dot eyes are a huge tell too though lol

also it seems the kuroi drawing in between miyuki kuroki and masunari's stuff says まじま, which points me towards takahiro majima, but im not going to go out on that limb just yet