Around 2.25am Indian time on Friday, when Nasa’s 1,026kg Perseverance rover landed on Mars after completing a 472-million- km journey, an announcement was made in the mission control room of Nasa’s Jet Propulsion Laboratory (JPL): “Touchdown confirmed.” Standing among the proud team members amidst the thunderous applause was Swati Mohan, a Bengaluru-born scientist who made the critical callouts while Perseverance was executing the nerve-wracking entry, descent and landing (EDL).
Mohan was the mission’s guidance, navigation and control lead that executed the final manoeuvres, including the landing that Nasa called the ‘seven minutes of terror,’ on the 45km wide Jezero crater. A PhD in aerospace, aeronautical and astronautical engineering from MIT, Mohan visits her relatives and friends in India every four or five years.
From the time Perseverance entered the Martian atmosphere at 19,300kmph till it landed seven minutes later, Mohan made callouts like “cruise stage separation confirmed”, “Perseverance enters Martian atmosphere”, “Parachute successfully deployed,” “heat shield separated,” and, finally, touchdown confirmed.”
The Jezero crater is considered hazardous for landing. Mohan played a crucial role in developing the landing system that helped Perseverance autonomously avoid danger zones and touch down safely.
Called the ‘terrain relative navigation (TRN)’, it was the eyes and ears of Perseverance while executing the final manoeuvres. In an email interview to TOI in July, Mohan said the navigation system would allow Perseverance to land with “open eyes”. She explained that a camera would take pictures of the ground as Perseverance descends on a parachute. “This is like putting your hands out in front and stopping when you feel the ground. Previous missions have relied on radar to land,” she said. It was tested over a desert in California before the mission.
The mission had another Indian connection: Bob Balaram, a graduate from IIT-Madras, worked as the chief engineer for the Ingenuity helicopter, a technology demonstrator, which landed on Mars with Perseverance. Ingenuity is expected to make its first test flight in 60 to 90 days.
Asked why Nasa chose a landing zone that has steep slopes and rocks, Mohan said the Nasa science team believed this ancient river delta could have collected and preserved signs of microbial life if they were ever there.