Why in News:

• Vela, the fourth submarine of P75 of the Indian Navy, was commissioned at the naval dockyard. 
  • Project 75 entails the construction of six Scorpene-class submarines. Three of the six submarines, Karanj, Kalvari, and Khanderi, have already been commissioned. The fifth submarine, Vagir, was launched in 2020 and is undergoing sea trials while the sixth one Vagsheer is in advanced stage of outfitting.

About INS Vela

• The C303 anti-torpedo countermeasure system and anti-ship missiles are installed on this submarine.
• It’s a diesel-electric attack submarine.
• It also has a Permanently Magnetized Propulsion Motor that is completely silent.

About Scorpene class submarines

• They are the most advanced conventional submarines with superior stealth features, such as advanced acoustic silencing techniques, low radiated noise levels and ability to attack with precision-guided weapons on board.
• The Mazagon Dock Limited (MDL) is building six Scorpene submarines with help(technology assistance) from the Naval Group of France.
  • MDL( public sector undertaking shipyard) is under  the Ministry of Defence.
• These are used in the missions such as area surveillance, intelligence gathering, anti-submarine warfare, anti-surface warfare and minelaying operations. 
• It can carry upto 6 torpedoes, heavy weapons and  can go submerged upto 21 days. 

 References:

1.  https://www.thehindu.com/news/national/navy-commissions-submarine-ins-vela/article37677238.ece
2. https://indianexpress.com/article/explained/explained-ins-vela-submarine-indian-navy-7639778/