In 1977 he was called up for military service and, following his request, he was sent to the Paratroopers Training School (SMIPAR) in Pisa. After completing basic training at the Recruits’ Training Centre (CAR), he attended the Parachuting Course and obtained the Parachuting Licence in February 1978.

Instead of being assigned to the operational departments, he was selected as Assistant Instructor of Parachuting (AIP) and remained in force at the gymnasium of the SMIPAR where, for the time of the remaining military service, he assisted the non-commissioned officers instructors of Parachuting in delivering training courses to parachuting trainees, first as a Corporal and then as a Chief Corporal instructor.

In November 1978, at the end of the compulsory military service, he decided to re-enlist. He was promoted to the rank of Sergeant and began his career in the Italian Army as a non-commissioned officer instructor of parachuting, a position he maintained until December 1979 when, after responding to a call for a special recruitment of Army Raiders, he joined, as a Raider Trainee, the ranks of the 9th Paratroopers Assault Regiment "Col Moschin" of Livorno, a Special Forces Unit of the Italian Army. In the following two years, he completed the basic courses (80/B, Skiing, Mountaineering, Controlled Opening) and in August 1982 he joined the 2nd Raiders Company, as a member of the Special Operations Unit.

In September 1982, following the massacre of Sabra and Shatila in Beirut, Lebanon, and the establishment of the Italian Contingent of the Multinational Peace-Keeping Force (ITALCON), he was sent to Beirut with the Raider Battalion with the rank of Sergeant Major. During the first two months he worked in support of the various checkpoints in the Palestinian camps and at the airport, and worked with the Mine Clearance Unit for the removal of land mines and unexploded ordnance scattered throughout the country. He then joined the Command of the Italian Contingent where he worked for the "Arab Office”. This Office supported Contingent Commander General Franco Angioni, under the coordination of Captain Corrado Cantatore, and was tasked collecting and managing operational information as well as managing the relations with the press and handling communication in general. He remained in this function until the Contingent was repatriated in February 1984.

His training as a raider, combined with his operational experience in Beirut, in an unstable, yet highly challenging context of constant risk, allowed him to refine his skills of adaptability and problem solving, and also to develop an approach of flexibility that will prove to be essential for the future.

As part of his duties in Beirut, he escorted many Italian and foreign journalists who came to visit the Italian contingent. Prominent among them Oriana Fallaci, who would then take numerous trips to visit both Beirut and the Italian contingent. A relationship of deep professional and personal appreciation developed between the two to the extent that, on the ship leaving Beirut upon the withdrawal of Italy’s contingent, he confessed to her that as a child he dreamed of ‘becoming an astronaut’: and she encouraged him to pursue that dream.

In the meantime he won the competition to become an officer of the Army and in June 1984 he became Second Lieutenant. He was assigned, for the necessary refresher and training courses, first to the Scuola di Applicazione (School for Military Officers) in Turin and then to the Infantry and Cavalry School in Cesano. In April 1985, being convinced of the need for a change in his life and having become finally aware of his physical and psychological skills, he decided he would pursue his dream of becoming an astronaut.

He got a two years' leave from the Army and enrolled in the Department of Aerospace Engineering of the Polytechnic Institute of New York University, where he also had a chance to learn English: until then he had only known French as a foreign language. Having realised that he was progressing in his studies successfully, in April 1987 he finally left the Army and continued to work relentlessly to complete his studies as an engineer. In June 1988 he obtained his Bachelor of Science in Aerospace Engineering and enrolled in the Master of Science in Aeronautics and Astronautics.

In 1988, the National Space Plan (PSN), forerunner of the Italian Space Agency, signed an agreement with NASA to send the first Italian Payload Specialist to space aboard the Space Shuttle, in order to monitor the operation of the Tethered Satellite System (TSS), an experiment designed by Italian scientists.

In February 1989, the PSN published a competition notice for the selection of 2 Payload Specialists to be sent to NASA and began the selection process among the candidates who applied for the competition. Paolo was among those candidates. The multi-level selection procedures lasted a few months and culminated in the final selection carried out during the Investigator Working Group (IWG) meeting at Stanford University. Although he was among the finalists, Paolo was not selected.

After completing his Master of Science in Aeronautics and Astronautics in New York in September 1989, Paolo returned to Italy and immediately began working with Proel Tecnologie in Florence as a design engineer. He was mainly involved in the final testing stages of the Electron Gun, one of main devices of the Tethered Satellite, as well as in other projects dealing with thermionic equipment for space applications.

In May 1990 he responded to a European Space Agency (ESA) call for volunteer candidates on whom the physical and psychological selection tests - to be performed in the upcoming selection of ESA astronauts - would be carried out. The 10 winners were sent to the Norwegian Underwater Technology Center (NUTEC) to participate in a simulated space mission called Experiment for the European Manned Space Infrastructure (ExEMSI), a simulation in which the “emsinauts" are isolated and confined for 28 days in a module of the NUTEC hyperbaric chamber to carry out a technical-scientific program, typical of a mission on the International Space Station. Paolo was selected as one of the six candidates who would be isolated, and then as mission commander. The simulation, whose main objective was to study the group dynamics in an isolated and confined environment under high levels of stress, ended in October 1990.

In November 1990, ESA issued a call for proposals intended for an "Astronaut Training Engineer" at the European Astronaut Centre (ESA/EAC) in Cologne, Germany. Paolo responded and passed the selection. In January 1991 he moved to Cologne where, at ESA/EAC, he was involved in the development of the training and qualification curriculum of European astronauts and was in charge of creating the Astronaut Training Database.

In 1992 he took part in the call for proposals targeted to the selection a new group of European astronauts, but did not pass the selection procedures at the national level, which was carried out under the aegis of the Italian Air Force.

In 1994, ESA/EAC temporarily assigned him to the EuroMir95 project, a joint project of the European Space Technology Centre (ESA/ESTEC) in Noordwijk, in the Netherlands, and the Russian Federal Space Agency in Moscow, for preparing and implementing the first long duration European space mission. The mission was carried out in 1995-96 on the Russian space station MIR. From 1994 to 1996, Paolo spent his time between Cologne, Noordwijk and Moscow, having the role of engineer in charge of creating and managing the information system for on-board collection, transmission, and dissemination on Earth of the scientific data of the mission.

In August 1996 Paolo was transferred to NASA's Johnson Space Center (NASA/JSC), in Houston, Texas (USA), to represent ESA in the development of the International Curriculum of Basic, Advanced and Mission Training for the International Space Station (ISS). The assignment had a length of 1 year initially, but was later extended by one year until August 1998.

In February 1998, the Italian Space Agency issued a call for proposals intended for two Italian astronauts to complete the Italian quota of the European Astronaut Corps, just set up by the European Space Agency. Paolo participated and successfully completed all the phases and was finally selected as an astronaut in July 1998. He then became one of the new ESA/EAC astronauts in Cologne and was immediately transferred to the Johnson Space Center in Houston where, in August 1998, as an Astronaut Candidate, he began training as a Mission Specialist (Space Shuttle and International Space Station) in NASA Astronaut Group 17.

He spent two intense years, with the other astronaut candidates of his class, in basic training to obtain the qualifications of Mission Specialist (i.e. a crew member) of both the Space Shuttle and the International Space Station (ISS). The courses included theory lessons, simulations in different simulators, visits to a number of NASA centres throughout the United States, survival training in different terrestrial and marine environments as well as field lessons such as, for example, a practical course of geology. Candidates are assessed both for their technical learning skills and for their practical and attitudinal skills in teamwork and in high-stress situations.

In August 2000, NASA Astronaut Group 17 completed their courses and Paolo received the Astronaut Silver Pin, having become a qualified astronaut awaiting a space mission. Paolo began working within the NASA Astronaut Corps in Houston, performing various technical tasks while honing and enhancing his skills, with advanced training courses, as an operator of the Space Shuttle Remote Manipulator System (RMS) as well as his qualification for spacewalking (EVA). He also attended a course for Flight Engineers onboard the Russian shuttle Soyuz at Gagarin Cosmonaut Training Center (GCTC) of StarCity, in Moscow, and participated in field expeditions in Alaska and Wyoming, aimed at testing performance and group dynamics in high stress environments.

In July 2006, he was assigned to the STS-120 mission (the 120th mission of the Space Shuttle conducted on the Discovery Shuttle), i.e. a complex mission for the construction of the International Space Station, whose main objectives were to connect a new construction module, called Node 2, to the station and to reposition the P6 solar panel array. As a flight engineer, his main roles were the following: operator of the Space Shuttle mechanical arm (RMS) through the inspection phases of the heat shield, coordinator of all space walks, and mission specialist number one (MS-1) in the space shuttle re-entry phase.

He started a relentless training activity - mainly in Houston and Cape Kennedy - in which he was involved full time with the rest of the crew until the launch.

The mission was launched from Cape Kennedy on October 23, 2007 and ran smoothly until the eighth day when a tear appeared in one of the repositioned solar panels, a serious problem for which the mission had to be stopped and rescheduled. The mission was extended by one day to allow the Houston Control Center to evaluate all possible options. It was decided to take an off-nominal space walk to repair the solar panel. Accordingly, five laces, to be placed on the solar panel, were built with makeshift material inside the station, and some tools were prepared to perform this operation.

The mechanical arm of the station, holding the OBSS boom for on-orbit inspections and an additional small platform on top, were used to position the astronaut near the panel. The mission was extended by one more day to allow the crew to prepare all the necessary tools and get ready. During the complex and challenging spacewalk, carried out on the 12th day of the mission, the solar panel was repaired and its functions were fully restored.

Upon completion of the EVA, the mission was extended one more day to allow the crew to rearrange the station and the shuttle equipment and to focus on the complex phases of return. The Space Shuttle Discovery returned to Cape Kennedy on November 7, 2007, after spending 15 days, 2 hours, 23 minutes in orbit, a record for Space Shuttle Discovery. On his return to Houston, the President of the United States, George W. Bush, personally congratulated the crew for the mission accomplished. Just like other astronauts after completing their first space mission, Paolo received the Astronaut Gold Pin.

On his return from the mission, he received an excellent assessment of his performance and was told that he would soon be assigned to a new shuttle mission with spacewalks. For this reason, he was given the technical task of supporting the EVA division of the Astronaut Office. However, the assignment was redirected to another astronaut and Paolo kept waiting in Houston. In July 2008, the opportunity of a long-duration flight for an Italian astronaut on the station was announced and Paolo was the main candidate. Because of the reservations put forward by the Italian Space Agency and the Italian Air Force, it took several months for the assignment to be ratified, which happened only after the flight option was taken over by the European Space Agency.

In December 2008, with a delay of several months, Paolo began training for ISS Expedition 26/27 to the International Space Station. He was assigned the role of Flight Engineer (FE) of the Soyuz TMA-20 spacecraft for the launch, approach, docking, and landing phases, the role of Flight Engineer (FE) for ISS Expedition 26, and the role of head of the American space segment (which includes the European and Japanese laboratories) for ISS Expedition 27 (the latter corresponding to the role of deputy station commander, when the commander is Russian).

Moreover, as for both ISS Expedition 26 and ISS Expedition 27, he was a member of the standby team, that would have to carry out emergency spacewalks in case of need.

After two years of ceaseless training between StarCity, Houston, Canada, Japan and a number of European sites, on December 15, 2010, Soyuz TMA-20 was launched from the Baikonur cosmodrome to the ISS. In his role of Flight Engineer (FE), Paolo was tasked with assisting the commander of the spaceship in all phases of launch, approach, docking and re-entry, and to react in case of malfunction, up to taking manual control of the vehicle in the event of unavailability of the commander.

The launch and the entry into orbit took place without any problems and the spacecraft, following the procedures for approaching the station in use at the time, began the first of the 32 orbits it would complete before docking with the ISS, 49 hours after the launch. Periodically, when the spacecraft flew over the territory of Russia, fast radio links were established with the control center in Moscow. During this phase there were communication problems due to an incorrect configuration of the system on the ground and the spacecraft remained isolated, without communications, for several hours. Soyuz TMA-20 automatically docked with the station on December 17, 2010 and remained there until May 23, 2011, when it undocked from the ISS, for landing back on Earth. In the 157 days spent on the ISS Paolo carried out the typical tasks of a Flight Engineer, such as ordinary and extraordinary maintenance of the station, loading and unloading of resupply vehicles, support to the operations of the crews on the ISS, performance of experiments and of technical and scientific education activities, liaising with the press, and having video links with the institutions. Apart from a false alarm of atmospheric contamination, there were no serious malfunctions during the entire mission and it was not necessary to carry out emergency space walks. During the complex mission, several vehicles docked with and undocked from the station: 2 Space Shuttles (STS-133 and STS-134); 2 Soyuz spacecraft (TMA-01M, TMA-21); 4 resupply vehicles (ESA ATV2, JAXA HTV 2, RSA Progress M-09M, RSA Progress M-10M). Furthermore, six nominal spacewalks were performed: 2 Russian EVAs and 4 American EVAs.

At the moment of undocking from the station, an additional orbit was added to carry out a manoeuvre that had never been done before: photographing and filming the station connected with the Space Shuttle and to the European and Japanese resupply vehicles. Paolo was the crew member who acted as a photographer, while the Russian commander of the Soyuz manually kept the vehicle at the correct distance and altitude. Once the manoeuvre was completed, the Soyuz returned to Earth with a "soft landing" in the steppe of Kazakhstan. The landing took place on 24 May after 159 days, 7 hours, and 17 minutes.

On his return from the ISS Expedition 26/27 , Paolo received an excellent assessment from NASA of his on-board performance and was given the greenlight for a further space flight in the role of space station commander. However, conditions in Italy were unfavourable for him and, after the post-flight year in Houston, where he completed his scientific experiments and carried out routine rehabilitation and public relations activities, he was not allowed to maintain his astronaut qualifications and in 2013 he was first seconded to the European Space Research Institute (ESA/ESRIN) in Frascati, Italy and in 2014 to the European Astronaut Centre (ESA/EAC) in Cologne, Germany.

In this period he was engaged in supporting institutional activities of technical education. He participated in simulations of group performance and group dynamics in high-stress environments such as ESA CAVES (Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills) and NASA NEEMO (NASA Extreme Environment Mission Operations) where he was assigned the role of CAPCOM (Capsule Communicator at the Mission Control Center).

In 2015, following a change of government in Italy and in the top management of the Italian Space Agency, NASA assigned a long duration mission to Italy, a mission that is pre-assigned to Paolo. In August 2015, Paolo returned to Houston to resume training and renew his qualifications as station Flight Engineer and in EVA. In addition, he was sent to the Canadian Space Agency in Montreal, Canada to acquire the qualification of operator of the mechanical arm of the space station (SSRMS Space Station Remote Manipulator System). After successfully completing the training and retraining processes, in October 2015 he was officially assigned to the crew of ISS Expedition 52/53 and began mission training between StarCity, Houston, Japan and Europe, training which was completed in July 2017.

The mission was launched from Baikonur on July 28, 2017, on the Soyuz MS-05 spacecraft, and after a nominal launch and 4 Earth orbits (6 hours) it successfully docked with the International Space Station. On the Soyuz spacecraft, Paul had the task of Flight Engineer-2, the second Flight Engineer having the role of supporting the commander and the first Flight Engineer in performing spacecraft control.

In the 138 days spent on the ISS, Paolo carried out the typical tasks of the Flight Engineer: ordinary and extraordinary maintenance of the station, loading and unloading of the various refuelling vehicles, conducting experiments as well as technical, scientific, and education activities, liaising with the press, institutional video links. During the mission, several vehicles docked with and undocked from the station: 2 Soyuz spacecraft (Soyuz-MS04, Soyuz-MS-06) and 4 resupply vehicles (RSA Progress MS-06, SpaceX Dragon CRS-12, RSA Progress MS-07, Cygnus CRS OA-8E). In addition, 4 nominal spacewalks were performed: 1 Russian EVA and 3 American EVAs. Paolo was assigned the role of SSRMS (Space Station Remote Manipulator) operator for the undocking of the SpaceX Dragon resupply spacecraft, for the docking of the Cygnus cargo ship, and for supporting the spacewalks. The mission was completed on December 14, 2017 and they completed their journey back to earth with the usual "soft landing" in the steppe of Kazakhstan after 138 days, 16 hours, 57 minutes.

Upon return from the third mission, Paolo was engaged in post-flight activities: completing scientific experiments, carrying out rehabilitation activities, providing technical feedback on on-board tasks, carrying out institutional, educational and public relations activities. On October 31, 2018, one and a half years before the natural expiration date of the contract, ESA terminated, of its own motion, his employment contract and retired him. At that moment, after one short duration mission on the Space Shuttle, two missions on Soyuz and two long duration missions on the International Space Station totalling 313 days, 2 hours and 36 minutes, Paolo was the second-most experienced European astronaut in terms of flight experience.

Paolo’s work experience spans across: 8 years with the Italian Army as a Raider, 1.5 years as a design engineer, 6.5 years as an engineer in charge of astronaut training, 20 years as an astronaut. In all these years he has worked, acquiring theoretical and practical knowledge, in the preparation and management of technical activities as well as in operations in complex and hostile environments. Paolo established the company Astropaolo Srl, with a view to leveraging his extraordinary knowledge, skills and expertise in the fields of education and professional development. His goal is to reach out to and engage in a dialogue with anyone who is keen to look at the world from a different and unique perspective. Sharing, listening and constructively debating with others can be an opportunity to discover new things, even for someone who made his childhood dream come true.