INS Kattabomman (Project Skylark)

INS Kattabomman is the Indian Navy's very low frequency (VLF) transmitting station, located at Vijayanarayanam near Tirunelveli in Tamil Nadu, southern India. It falls under the Southern Naval Command. The station provides one-way communication with submerged submarines, which cannot receive higher-frequency signals at depth.

The facility occupies about 3,000 acres. Its VLF antenna system comprises 13 masts arranged in two rings around a central mast; the central mast stands 301 m, the inner ring masts 276.4 m and the outer ring masts 227.4 m. Transmission is on 16.3 kHz, 17.0 kHz, 18.2 kHz and 19.2 kHz. Two further masts carry an umbrella antenna at 471 m, the tallest structure in India and the tallest military structure in the world.

An extremely low frequency (ELF) transmission facility adjoins the VLF site. It is operated for the Nuclear Command Authority to pass release and alert traffic to the Arihant-class ballistic missile submarines. India is the second country after Russia to operate an ELF station in active service, the United States having ended its own ELF transmissions in 2004.

Work on the station began in 1984 under the designation Project Skylark at a cost of ₹122 crore, and it was commissioned by President Ramaswamy Venkataraman on 20 October 1990, making India the seventh country with an operational VLF communications capability. Construction of the ELF facility began in March 2012, and it entered service in 2014. A new VLF installation, contracted to Larsen & Toubro and incorporating a digitised control interface, was inaugurated on 31 July 2014.