Robert Kubica, the first Polishman to compete in Formula 1, not to mention the first Pole to win a Grand Prix, has endured some intense peaks and troughs in his racing career. From replacing Villeneuve in 2006, to enduring a horrific 75 G crash at the 2007 Canadian Grand Prix, then winning the same race the following year. He was later involved in a career-derailing rally crash in 2011 that nearly severed part of his right arm, but has since bounced back, winning the 2013 WRC2 championship, and competing in the WRC in 2014.
He did some Formula 1 simulator work in 2013 with Mercedes, but his right arm's limited range of motion due to his 2011 crash meant that tighter circuits with heavy steering input such as Monaco were exceedingly difficult for him. As a result, ambitions of returning to Formula 1 were shelved... for the time being, that is. Today, Kubica participated in a Formula 1 test drive with Renault Sport F1, his former team for 2010, driving the 2012 Lotus E20. The Enstone team raced under the Lotus name between 2012 and 2015, which is why they have access to said car.
This is the third test in a series of escalating single-seater runs in which Kubica has been testing his physical limitations; specifically, those of his right arm, as he has already worked out GP3 and Formula E cars in Italy and England respectively this calendar year. Mark Hughes of Motorsport Magazine posits that this test means more than just a nostalgia trip for Kubica and Renault—the Pole may be working his way up to testing the 2017 cars, and if he proves himself, he could end up as the team's replacement for foundering driver Jolyon Palmer.
Another prominent driver in competition for a Renault seat is Sergio Perez, who has been scouted by the team. Supposedly, Kubica has been more than competitive in simulators of current Formula 1 cars. How today's test went will be known in the near future, but going by the news so far, Kubica climbing behind the wheel of the RS17 could happen before we know it.