Context: 

The Navy’s Kilo­class submarine INS Sindhuratna which underwent a major upgrade in Russia reached Mumbai after sailing for 97 days.

INS Sindhuratna:

• INS Sindhuratna is a Russian Type 877EKM diesel-electric submarine also popularly called a NATO-defined Kilo-class sub.
• INS Sindhuratna is a Sindhughosh class submarine.
• The submarine underwent a Medium Refit Life Certification (MRLC) process in Russia which extended its life.

India’s submarine strength:

• India has 17 conventional diesel-electric submarines, classified as SSKs, but many of its SSK submarines require mid-life upgradation. 
• The fleet includes 
  1. Seven Kilo-class
  2. Six French Scorpene submarines
  3. Four German HDW submarines
  4. The indigenous nuclear ballistic missile submarine INS Arihant

Maritime Capability Perspective Plan (MCPP):

• According to the Maritime Capability Perspective Plan (MCPP), the Indian Navy is planning to have 200 ships by 2037. 
• The MCPP also laid down a 30-year (2000-2030) roadmap to build 24 submarines — 18 conventional submarines and six nuclear-powered submarines (SSNs) by 2030.
• The Indian Navy’s present naval strength comprises about 130 ships and submarines.

News Source: The Hindu