Forlì in the field to defend the Earth from the risk of asteroids

"We have two years to prepare, the satellite will arrive at its destination in October 2026, in June 2027 the probe will enter orbit, and after a couple of months it will also release the two cubesats with cameras, radar and various instruments. In the meantime, as managers of the radioscience experiment of the Hera mission, we will prepare all the data analysis to be ready to measure the mass of the binary asteroid'. Paolo Tortora, professor of Aerospace Systems and Systems at the University of Bologna's Forlì campus, is excited. He was reached by phone as soon as he landed from Cape Canaveral, where he and four colleagues from the department witnessed the launch of the ESA (European Space Agency) spacecraft dedicated to the defence of our planet last 7 October. For the first time in human history, a spacecraft will investigate the changes in the orbit of an asteroid knowingly hit by a probe launched from Earth to divert its course. So as to be ready one day to deflect celestial bodies on a collision course with the globe, as in the film 'Don't look up' and in the whole repertoire of disaster films about falling space debris.

Hera is a small mission, 300 million euro in investment, but developed in record time, with a hundred or so European companies and institutes involved, and a leading role for Italy, which covers about a third of the budget and half of the staff. "Together with us and Inaf (National Institute of Astrophysics), the University of Pisa is also involved in the radioscience experiment, while the University of Padua is involved in the scientific side of the mission. Our radio transponder was built by Thales Alenia in its laboratories in Rome, and the Turin-based Tyvak, with the Milan Polytechnic, built one of the two nanosatellites, named not by chance after the Pisan mathematician Andrea Milani, the first to conceive of a planetary defence mission with the sending of two spacecraft, one to deflect the target asteroid and a second probe to collect the impact data,' explains Tortora, director of the University of Bologna's Ciri-Centro Interdipartimentale di Ricerca Industriale Aerospace, who was also appointed a few months ago as a member of the technical-scientific council of the Italian Space Agency (Asi).

The mission to deflect Dimorphos, the small moon revolving around the asteroid Didymos, was carried out two years ago by NASA, which crashed its Dart (Double Asteroid Redirection Test) spacecraft into the secondary body. A 600 kg projectile crashed at a speed of 7 km per second into a 170 metre diameter rock, itself in orbit around its sun, an 800 metre Saxon (it is easier to deflect the moon's orbit than that of the main planet). 'Proportionally,' explains the space engineer, 'it's like a 0.1 gram gnat hitting our 1,000 kg car while it's travelling, but at that speed it still manages to change its gait. And indeed, Dart reduced the orbital period of Dimorphos around Didymos by 33 minutes, about 5 per cent of its original value (a 12-hour round trip), thereby also modifying Didymos' motion in space. "The probe that was supposed to observe the impact against the binary asteroid should have been there before Dart's crash, but the European Space Agency in 2016 did not approve the mission, it did so only three years later. We will retrieve the information ex post, in two years' time,' Tortora assures.

The Hera mission is just one of the projects being followed by the Ciri Aeropace of Forlì for Asi, bringing together some fifty lecturers not only from the aerospace course but also from civil engineering, physics, astronomy, electronics and Tlc at the University of Bologna. "We won a call for the large Alcor nanosatellite programme, out of 20 missions the Alma Mater is involved in five. And we are also very active in the experiments on the international space station with several lead assignments,' says Tortora, who has returned to work on the Forlì campus - housed in the technology hub adjacent to Ridolfi airport - where he teaches together with some fifteen colleagues specialising in aerospace. "We are a younger, smaller and less renowned pole than the Sapienza in Rome or the Polytechnics of Milan or Turin,' he concludes, 'but the student-faculty ratio here is a record high (130 freshmen for the Bachelor's degree and 70 for the Master's degree, the Master in aerospace engineering) and is an enormous added value for laboratory activities.