Judge Jeremy Fogel is sitting by designation with the Federal Circuit this month. This is the first judge to sit by designation with the Federal Circuit since Judge Prost took over the Chief Judge position last year. There was a dramatic drop off in judges sitting by designation after Chief Judge Michel retired.
By the way, I believe it is not unprecedented for retired judges to sit by designation — retired Justice Sandra Day O’Connor sits by designation frequently (although never before with the Federal Circuit). It would be fun to have Chief Judge Michel back sitting by designation.