AUTOSPORT revealed last month that Karthikeyan would race in India, slotting in for a one-off appearance in place of Vitantonio Liuzzi.
The 34-year-old Indian has been given practice runs since the Singapore Grand Prix to prepare for him for him home bow in next weekend's race.
"Driving in front of the home crowd cheering on is a once in a lifetime experience and I feel extremely fortunate," he said.
"It's going to be a surreal experience. There is a huge buzz around the grand prix already and I'm sure that it'll be a resounding success.
"For sure I'll race hard and try to get a good result for myself and the team."
Karthikeyan said he was also hoping to be part of a lasting motorsport legacy within his home country, and to "motivate more youngsters towards the sport and give us future F1 drivers.
"Making it into F1 at the time I did was a seriously uphill task and the thought of being able to compete in the inaugural Indian GP was non-existent. But it is finally here and I'll be on the grid."
Team Principal Colin Kolles said Karthikeyan would only drive in India, but said his presence made the Indian Grand Prix feel like a home race for the team.
"Despite not being the most popular sport in India, the excitement around the Grand Prix makes us think that it will be an extremely popular event," Kolles said.
"And for HRT, it is even more special. Having Narain Karthikeyan, the first Indian driver in F1 history, and Tata with us makes it feel like a home race.
"Narain is a talented driver and we are proud to be going down this path with him. I have asked Tonio Liuzzi to step aside for the Indian GP and I have to thank him for his professional approach and attitude."