Most of the data collected in April 2017 EHT global campaign have now been through a first stage of processing at the MIT Haystack Observatory (Cambridge, MA, USA) and the Max Planck Institute for Radio Astronomy (MPIfR; Bonn, Germany). Computing clusters at these facilities have combined signals from sites around the world to produce "raw" data sets. Now the exciting task of further processing and analyzing these data is underway within a number of focused working groups. These groups are calibrating the data to remove instrumental effects and formatting the output for imaging and science analyses that will look for the black hole "silhouette" and the signatures of orbiting matter around the target black holes. Each of those groups is vitally important for ultimately reaching the EHT science goals.

The only part of the 2017 dataset we are still missing is from the observations performed with the South Pole Telescope. The data are currently on their way from the South Pole, where the beginning of the austral summer makes it possible for our team to retrieve the data storage disks that have been in "cold" storage since April. By mid-November, they should arrive at Haystack Observatory and MPIfR, where they will be combined with the rest of the data. A small fraction of data, however, were sent back from the South Pole via satellite, so we have already confirmed that all the sites in the EHT worked well.

Work is continuing on development of imaging algorithms. September 6 marked the end of the latest EHT Imaging Challenge, in which members of the EHT team applied different imaging techniques to "fake" EHT data sets created from known test images. Their submissions will be critically examined at the Imaging Workshop taking place on October 10-12 at the Black Hole Initiative in Cambridge, MA. This blind testing by using a variety of different approaches is the best way to compare techniques and to build confidence in the imaging power of the EHT.

Shep Doeleman,

EHT Director

