Over the past 4 years a community effort has been carried out to revise entirely the historical Sunspot Number series. A good overview of the analyses and identified corrections is provided in the recent review paper:
Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E. W.,“Revisiting the Sunspot Number. A 400-Year Perspective on the Solar Cycle”, Space Science Reviews, Volume 186, Issue 1-4, pp. 35-103.
Now that the new data series has been finalized, we are about to replace the original version of our sunspot data
by an entirely new data set on July 1st. On this occasion, we decided to simultaneously introduce changes in several conventions in the data themselves and also in the distributed data files.
There are so many diverse changes that we cannot guarantee that everything will work perfectly on the first try.Our team is too small to make full prior simulations. Therefore, multiple careful consistency checks will be done on July 1st itself, which will slow down the processing. So, please anticipate some delays compared to an ordinary month.