Why was a highly elliptical orbit useful?

On 5 November 2013, a PSLV rocket, PSLV-C25, launched India's Mars Orbiter Mission. When the spacecraft entered orbit around Mars, the Indian Space Research Organisation (ISRO) became the fourth space agency in the world to send a spacecraft into orbit around the red planet.

The mission had two kinds of aim. The first was technological: to design and operate a spacecraft that could make the long journey and enter orbit around Mars, able to act on its own when needed. The second was scientific: to study the surface of Mars, the shapes of its land, its minerals and its atmosphere, using five instruments, among them a colour camera and a sensor built to look for methane.

The spacecraft was placed in a highly elliptical orbit, a path shaped like a stretched circle. When it was farthest from Mars, its camera could photograph the whole planet at once; when it swung close, it could capture fine detail.

The orbiter was designed to last six months. It went on working far longer, and on 24 September 2021 it completed seven years in orbit. Its camera took more than 1,100 images, which were used to publish a Mars Atlas, and the mission gave the first view of the far side of Deimos, one of the moons of Mars. It also became known for its low cost: about 450 crore rupees.