Sloan has been through two phases of operation already, and now SDSS-III is about to start, incorporating four separate surveys, each with a different mission. The first, BOSS, will look once again at very large scale structure in an attempt to measure the acceleration of the expansion of the Universe. While Sloan was able to do this in its previous guise (in fact, this was part of its original raison d’etre) the new observations will, according to David Weinberg ‘turn [this technique] into a precision tool for studying this cosmic acceleration’. Weinberg is wearing a very silly green cap with the roman numeral ‘III’ on it, but we’ll forgive him that because he said the project will include more imaging, particularly of the southern sky. That will gives us 2000 more square degrees to Zoo someday.

The second survey, SEGUE-2 will look hard at 140,000 more stars within the Milky Way that includes many of the exciting weird ones I blogged about the other day. It has first priority for ‘dark time’ (with the Moon out the way) for the next year, and a later program will catch another 100,000 brighter stars.

The third survey, APOGEE is, according to David, ‘a really revolutionary experiment’, looking in detail at 100,000 red giant stars. Less than a thousand of such stars have data of this quality to date, so this is a huge step forward. I’m particularly excited by their plans to map the distribution of 10 chemical elements throughout the Milky Way, which will be very interesting to say the least.

Extra-solar planets is a massive field of research that didn’t exist when the first discussions about what became the Sloan Digital Sky Survey took place. With the fourth and final survey, MARVELS, Sloan is getting in on the planet-hunting action. The plan is to visit each of 11,000 stars 30 times over a period of 18 months. It’ll be looking for the wobble caused by giant planets in orbit around these stars, revealed in the Sloan spectrum. They’ll deliberate target giant planets, in order to get enough data to really test the models of planet formation that have been constructed in response to their presence close to their parent stars (something literally no-one predicted before the observations began to roll in). The forecast is that MARVELS should find 150 planets after 6 years of observations.

The outlook looks good for many more years of Sloan science. To me, as an outsider looking in, there’s a changing of the guard feeling as universities and people join and leave the team. This is a natural part of Sloan’s evolution from the experiment it was to the observatory it is today but the strong commitment to keeping data public will ensure that – wherever people gather for the 25th anniversary in 2013 – there will be plenty more wonders ahead.

Update : Second report is now up too.