SEPIA is a single-pixel heterodyne receiver with a cryostat that can accommodate 3 ALMA-like receiver cartridges.

The tertiary optics to illuminate the SEPIA cartridges inside the Nasmyth cabin A of the APEX telescope were designed, constructed, and installed by the Group for Advanced Receiver Development (GARD) at Onsala Space Observatory (OSO) in Sweden. The SEPIA cryostat was also manufactured by the GARD team.

As from 2020, the three receivers inside SEPIA are the following:

  • SEPIA660 covering the window 597 – 725 GHz
  • SEPIA345 covering the window 272 – 376 GHz
  • SEPIA180 covering the window 159 – 211 GHz

Only one of the three receivers can be used at a given time, but the switch between receivers is very fast, taking only a few minutes to switch between bands.