Tracked Transit System (TTS) loop is off-by-one satellite terminal building; the 180-degree curve is under Apron A.

See aerial image of cut-and-cover construction in 1988:

  https://www.pprune.org/aviation-history-nostalgia/630332-stansted-airport-history-nostalgia-4.html#post10730234
  https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/1613x1210/stn8_62ff416d0b95c3ab45f4b5e16ccb8aebc729d726.jpg