The much-anticipated first official World Superbike test of 2011 starts at Portimao, in Portugal, tomorrow (Wednesday).

The three-day outing is the first of two official pre-season track sessions. The second will be at Phillip Island, Australia, from February 21-22, shortly before the first race of the year.

All seven 2011 WSBK manufacturers will be present in Portimao (although the factory BMW team will be missing), ready to measure their relative progress against their peers. On paper, every manufacturer has at least one rider capable of challenging for the title, and testing will give the first indications of which machinery is up to the challenge.

The benchmark will be reigning champion Max Biaggi and his factory Aprilia RSV4. Biaggi will once again be joined at the Alitalia team by rapidly rising WSBK star Leon Camier, who expects machinery of closely spec. to Biaggi this year.

There will be three high-class Aprilia riders in 2011 thanks to the new Team Pata entry for 2009 WSBK title runner-up Noriyuki Haga. The Japanese SBK legend is confident he can fight for the title despite his satellite status.

BMW Motorrad Motorsport's official team of Troy Corser and Leon Haslam is not attending the Portimao test, as the factory effort heads to its own sessions in Australia.

However, the BMW Motorrad Motorsport Team, promoted from the FIM 1000 Superstock Cup series to full WSBK status, will have their two riders out in Portugal. Former double world champion James Toseland and new Superstock champion Ayrton Badovini have the potential to be as potent as the official squad, once fully prepared for the new season.

Ducati's official team may have withdrawn from WSBK, but three Ducati teams will test in Portugal. Third in last year's championship Carlos Checa looks to have inherited leading Ducati status for the Althea Racing team, while the new Liberty Racing outfit has signed Jakub Smrz and Sylvain Guintoli. Supersonic Racing has top Superstock competitor Maxime Berger as its lone rider in 2011.

The Japanese manufacturers are heavily represented in WSBK racing once more in 2011, and a famous name in World Superbike history returns to the fold this time around - Castrol Honda.

The 2011 version is a Ten Kate operated team and they will call on the services of proven winners Jonathan Rea and Ruben Xaus. They have recently tested in Aragon - a new WSBK venue in 2011 - but in very cold weather conditions, so they will be particularly keen to see the Portimao tests bathed in sunshine as the outside world gets to see their new sponsors' livery in motion.

Kawasaki will be back with an unprecedented number of all-new machines operating under full factory support - three. Tom Sykes is retained for another year, and has been undertaking extensive tests on the new Ninja ZX-10R.

New boy Joan Lascorz is an old Supersport hand, but a rookie in WSBK, and he is scheduled to test at Portimao as he recovers strength in his injured shoulder. Third rider Chris Vermeulen will not test until Australia, as he continues to recover from reconstructive knee surgery.

Suzuki Alstare has lone rider Michel Fabrizio on its GSX-R1000 this year, a proven race winner on a bike that challenged Biaggi almost all the way last year in the hands of Leon Haslam.

Yamaha's new duo of factory stars will also be testing at Portimao, with Eugene Laverty already making a good transition from WSS to WSBK and MotoGP race winner Marco Melandri hoping to ride to the level he knows he can, after a recent operation to his shoulder.

A resurgence of interest and entries in the World Supersport Championship means that there will be over 20 riders at the Portimao test.

Headliners include Hannspree Ten Kate (Fabien Foret and Florian Marino), Parkalgar Honda riders Sam Lowes and Miguel Praia, plus Broc Parkes and David Salom from the Provec Motocard.com Kawasaki squad.

Gino Rea is also hoping to move on with his Step Racing Honda, while another rider with big credentials in many forms of racing, James Ellison, moves to Supersport with Bogdanka Honda, alongside Pawel Szkopek.

Possibly the biggest pre-season surprise is a late change of machinery for the ParkinGO Team, which will see Chaz Davies and Luca Scassa now running with Yamaha machines, the same ones which took Cal Crutchlow to the WSS Championship in 2009.

Triumph as a manufacturer will now only be represented at the test by Marko Jerman (MD Team Jerman).