This section describes relevant changes for observations to take place during Period 104

General

• The upgrade of the APEX telescope was completed in April 2018. It consisted of:
  • the replacement of the M1 surface panels with panels of higher accuracy, optimizing the telescope efficiency for high frequencies;
  • the replacement of the entire secondary unit with a new wobbler, allowing to switch between on and off positions separated by up to 10' at a rate of up to 2 Hz;
  • new telescope drives;
  • a new shutter mechanism.

In parallel, a new set of facility instruments is being installed (SEPIA and nFLASH), which replace the decommissioned SHFI.

• The preliminary dates for the ESO observing time in Period 104 are 15 August to 9 September, 26 October to 6 November and 9 to 19 December. Time critical observations should only be requested within these time slots.
  
• The ESO share in the APEX collaboration has increased from 27% to 32%. The exact distribution of the observing time between the APEX partners can be found on the APEX web pages.
• In order to solicit longer normal programmes for observations that do not require the best weather conditions, the maximum length of normal programmes on the instrument PI230 has been raised to 199 hours. For any other instrument, the limit remains 99 hours. Any PI230 programmes requiring 200 hours or more should also be requested as Large Programmes.
• Large and Monitoring programmes will only be accepted for ARTEMIS and SEPIA (SEPIA-180 and SEPIA-660).

Instruments

• ARTEMIS: in Period 103, both the 350 and 450 μm channels are offered for simultaneous observations. This instrument is optimized for wide-field mapping of areas of at least 4'x2', and achieves similar mapping speeds at both wavelengths. An observing time calculator is available.
  
• LABOCA: The 870µm bolometer array is offered in Period 103 depending on a sufficient demand and a successful completion of the re-commissioning activities in the Cassegrain cabin. No Large or Monitoring Programme proposals will be accepted for LABOCA, as its capabilities are expected to be superseded by a new bolometer array that has a wider eld-of-view, namely, A-MKIDs.
• nFLASH: This new Facility Instrument may not be ready in time for Period 104. Its capabilities are temporarily covered by PI230 and FLASH (the latter only in collaboration with the instrument team). Note that no simultaneous 230 and 460 GHz observations will be possible before nFLASH has been commissioned, which is expected in the 2nd half of 2019.
• PI230: This 230 GHz receiver covering from 200 to 270 GHz is offered as a temporary replacement of the nFLASH-230 receiver. It is a dual-polarisation, sideband-separating (2SB) receiver with an IF coverage of 8 GHz per sideband. There is a gap of 8 GHz between both sidebands. The backends are 4th generation Fourier Transform Spectrometers (FFTS4G) with 2×4 GHz bandwidth. A more detailed description is available in the presentation A-MKID, PI-230, LAsMA – new MPIfR receivers for APEX. An observing time calculator is available.
• SEPIA can house
  
  • 3 ALMA-type receiver cartridges with dual polarization, sideband-separating mixers (2SB)
    
    • SEPIA-180 (ALMA band 5) receiver, covering 159 to 211 GHz,
      
    • a new SEPIA-345 (ALMA band 7) receiver, covering 272 to 376 GHz,
      
    • SEPIA-660 (ALMA band 9) receiver, covering 578 to 738 GHz; note the extended frequency coverage with respect to the ALMA band 9 receivers.
      
  • Only the SEPIA-180 and SEPIA-660 receivers are available for Monitoring and Large Programmes.
  • The SEPIA-345 receiver is offered conditional to a successful commissioning in July 2019; any observations in this band will be executed with FLASH-345 instead if SEPIA345 is not available.
    
  • All receivers use the XFFTS backends, covering 4 GHz IF bandwidth coverage with a gap of 8 GHz between the image and the signal bands. For SEPIA-345 and SEPIA-660, this may be upgraded to 8 GHz bandwidth per IF and polarization with the expected commissioning of the new Facility FFTS4G.
  • An observing time calculator for all bands is available.
• FLASH: The 460 GHz channel of this instrument is offered as a temporary replacement of nFLASH-460. All prospective users are required to get prior approval from the PI team at MPIfR at least 2 weeks before submitting proposals for this receiver (contact: Bernd Klein, ). This requirement only refers to the 460 GHz receiver, and is not needed for the 345 GHz receiver. Simultaneous 345 and 460 GHz observations cannot be guaranteed, as FLASH is foreseen to be replaced by nFLASH during Period 104.
  
• CHAMP+: This MPIfR PI instrument is not offered since Period 101 due to ongoing re-commissioning activities.