The new Mercedes W03 was officially unveiled to the world’s press just prior to the start of the second week of official Formula One testing at the Circuit de Catalunya.

As seen in the spy shots earlier last week, the W03 features the stepped nose, similar to that of several other Formula One cars.

The new car has already been shaken down at Silverstone last week, and conducted a private test at Catalunya on Sunday – which the team were permitted to undertake because it had only been present for three of the four days of running at Jerez earlier this month.

Mercedes chose to stick with its 2011 car for Jerez in order to gain valuable data on this season’s Pirelli tyres, and was quickest on two of the days it was present – though it was running to full 2011 specification, including the no-longer-permitted exhaust-blown diffuser.

Norbert Haug, Mercedes motorsport chief, has commented that the W03 would not feature any radical innovations – contrary to speculation that the team had waited until the second test to reveal the car because it featured technical breakthroughs it did not want rivals to copy.

The most obvious outward change is the move to a stepped nose, in common with the majority of rival teams.

Having been unable to beat rivals Red Bull Racing, McLaren and Ferrari to race wins in its first two years, Mercedes GP is hoping to get among the top three on a more regular basis this season.

Last year it revamped its technical team with the addition of former Renault engineer Bob Bell, ex-Ferrari design chief Aldo Costa, and Geoff Willis, formerly of Williams, BAR and Red Bull Racing.

Nico Rosberg and Michael Schumacher continue in an unchanged driver line-up at Mercedes. With Schumacher coming into the final season of what was initially planned as a three-year comeback deal, speculation about whether the seven-time world champion will stay on into 2013 and beyond is likely to be one of the biggest stories around Mercedes this season.

The Williams-Renault FW34 has been revealed to the world’s press just a few hours before the start of the opening pre-season testing in Jerez.

After a very poor 2011 season, in which the Grove-based team scored just five points and finished ninth in the constructors’ standings, Williams are hoping for a changes in fortunes this year.

The FW34 is the first Williams to be produced since the major change of technical line-up at the team, which saw erstwhile technical director Sam Michael head for McLaren and co-founder Patrick Head step away from the Formula One side of the operation. Mark Gillan now leads the technical side of the operation.

The FW34 also sees the reunion of the multiple championship winning Williams-Renault partnership, as the Grove-based squad switches from its previous Cosworth V8s to the engine that powered Red Bull Racing to the last two titles.

On the driver side, Bruno Senna has replaced Rubens Barrichello, while Pastor Maldonado remains for a second season. Test driver Valtteri Bottas gets an enhanced role that will include some Friday practice running.

Team principal Frank Williams said: “One could say that looking at the Williams F1 Team today we are off to a truly fresh start. We have a new car, new driver line up, new engine and new senior personnel.

“We also have a number of new partners who have joined the team in the past few months. I’d like to take this opportunity to welcome them formally and sincerely wish that they have an enjoyable and, most importantly, a valuable experience with us. The team has had a good winter at the factory and we feel ready and strong for the fight.”

This is the car that all the Formula One teams must beat following the unveiling of the new RB8 from defending world champions Red Bull Racing.

The Milton Keynes-based squad hopes the Adrian Newey-designed machine will continue their ultra successful title winning run in 2012 with the Renault-powered RB8.

Having taken Sebastian Vettel to the last two drivers’ titles alongside its 2010 and 2011 constructors’ crowns, Red Bull Racing’s latest design is the most eagerly awaited of the new season contenders.

Adrian Newey, the man generally regarded as the key to Red Bull’s recent domination, is again responsible for leading the RB8 design.

The car appears outwardly similar to last year’s all-conquering RB7, which won 12 out of 19 races, but features a revised nose layout and a different exhaust to accommodate this season’s rule changes.

Attention has been focused on the stepped nose design on RB8 and close inspection reveals a possible f-duct system could be in place… Does Newey have an aero secret up his sleeve with the now dubbed ‘Bull-duct‘?

The line-up of Sebastian Vettel and Mark Webber remain unchanged for the fourth consecutive season. However, ex-Toro Rosso racer Sebastien Buemi is now Red Bull Racing’s reserve.

Video of the Red Bull Racing RB8 launch:

Scuderia Toro Rosso unveiled their latest contender for this year’s world championship with the STR7, ahead of the official start of Formula One testing at Jerez.

As expected, the STR7 features a stepped nose, similar to that seen in all the 2012 Formula One cars unveiled so far apart from the McLaren MP4-27, which opted for a different approach with a low chassis and nose treatment.

The Toro Rosso, powered by Ferrari engines for the sixth season, will be driven by Daniel Ricciardo and Jean-Eric Vergne after the team opted for an all-new line-up for the upcoming season.

Last year, the Faenza-based squad finished in eighth position in the constructors’ standings with Jaime Alguersuari and Sebastien Buemi.

“On Saturday (February 4th) at 10.00 am when loading the car I wasn’t convinced we could do it in time as there was so much snow, but we did it,” said team boss Franz Tost during the launch.

“The STR7 is the third car designed, fabricated and assembled completely by Toro Rosso. We have invested a lot of money to build up the infrastructure and I hope the results will be good in the forthcoming season. This investment was only possible because we have strong partners.

“Tomorrow (February 7th) we go out the first time with the new car and it is always something very special. We have two new highly skilled drivers and I am convinced both will do a very good job.

“Last year we finished eighth in constructors’ and this year we hope to do better, so seventh or more.”

The new car will take to the Spanish track for its debut run on the first official day of testing. Australian’s Ricciardo will have the unique honour to shakedown the new Toro Rosso STR7.