The first Task Force, with the mission of preparing two SOSUS locations north of Spitsbergen, is composed by the following subs:
BS-64 RFS Podmoskovye
K-371 RFS Pantera
To complete the mission, they need to use the Losharik minisub, on board the Podmoskovye. Each preparation takes 36 hrs
The BS-64 Pdmoskovye, originally launched as the K-64 from Project 667BDRM Delfin (Delta IV for NATO), was retired from active service on 1999 to be refurbished as mother sub for the minisubs of the Paltus class, and replace in this job the aging Yankee class KS-411. However, lack of funds would shelve this plan, although some jobs were completed, like retiring the "hump" housing the 16 nuclear SLBM and replacing it with a smaller hump, which presumably houses research equipment and crew spaces. Also, it looks like the Podmoskovye is nine meters longer than a regular Delta IV.
Podmoskovye at Zvezdochka shipyard, picture taken from Charly015's fantastic blog (http://charly015.blogspot.com.es/)
The Losharik (Projects 10830, 10831 and 210), on the other hand, is a nuclear powered "minisub" (with a length of 60 meters...), for research, rescue and presumably special operations. First of the class was launched in 2003 in Severodvinks, although little else is known about this subs.
Infographic with the internal arrangement of the Losharik, which allows her to reach great depths. Some sources claim diving depths around 6000 meters. Picture taken from Pakistan Defence forum (defence.pk)
Infographic with suspected or alleged capacities and sensors, same source as previous one
Mock-up of a Losharik with her mother sub
The escorting sub, the K-371 RFS Pantera, is an "old" Project 971 Shuka-B, Akula I for NATO, nuclear attack sub. The Akula class was one of the first Soviet designs which could challenge NATO nuclear subs. Armed with eight torpedo tubes, she is a very dangerous opponent: four of these tubes are 533 mm in size and can launch USET-80K torpedos along SS-N-15 Starfish (RPK-6 Vodopad) antisubmarine missiles, while the other four torpedo tubes are 650 mm and can launch the SS-N-16 Stallion (RPK-7 Vodopei) ASW missiles. They are also armed with some SA-N-8 Gremlin (9M36) SAMs. Pantera is one of the three surviving Akula I, from seven built, and she received some improvement on her quietening measures.
RFS Pantera in dry dock, picture taken from bemil.chosun.com forum.