When reading Soyuz 2-1B - Glonass-M Launch Updates on Spaceflight 101, I noticed an interesting photo showing these two red "horns" on the payload fairing (all photos courtesy of the Russian Ministry of Defence, here is an article in Russian, and English translation via Google Translate):
Their red color and that they don't really look strong enough to withstand acceleration during launch seems to suggest these are to be removed before launch and must be umbilical ports to access Fregat upper stage and the sole passenger - GLONASS-M satellite. This photograph seems to confirm the umbilical port part, as it looks like Fregat and GLONASS-M are being fueled / charged before the rocket is moved into its upright position:
Then, I've noticed they're still in place after moving Soyuz rocket vertically:
So this made me really curious;
What purpose do these red "horns" on the Soyuz 2-1B payload fairing serve? Is there more to them than merely being service / umbilical ports, or are they indeed removed before launch? If latter, why would they be still in place as the rocket is moved vertically?
To my understanding, the Fregat upper stage is loaded with 5,350 kg of UDMH + N2O4 (Unsymmetrical Dimethylhydrazine and Nitrogen Tetroxide fuel and oxidizer) long before that, during payload integration, but I'm not sure about GLONASS-M consumables (perhaps cold gas for ACS thrusters?), or if they both require grid power before switching to internal power minutes before launch? Is there any page available where their purpose is explained in more detail?