This section describes relevant changes for observations to take place during Period 103.

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 103 are 17 to 29 April, 19 to 30 June, and 15 August to 9 September. 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.
  
• Large and Monitoring programmes will only be accepted for ARTEMIS and SEPIA (band 5 only).

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 No Large or Monitoring Programme proposals will be accepted for LABOCA, as its capabilities are expected to be superseded by a new bolometer array that has a wider eld-of-view, namely, A-MKIDs.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 is offered depending on a successful commissioning in Q1 2019. It will contain two receivers replacing the SHFI/APEX-1 and SHFI/APEX-3 receivers: nFLASH230, covering from 200 to 270 GHz, and nFLASH460, covering from 385 to 500 GHz. Both are dual polarization 2SB receivers, and can be used simultaneously. The nFLASH230 receiver has an IF bandwidth coverage of 8 GHz with a gap of 8 GHz between the two sidebands; the nFLASH460 receiver has a bandwidth coverage of 4 GHz per sideband. The backends are 4th generation Fourier Transform Spectrometers (FFTS4G) with 2 x 4 GHz bandwidth. An observing time calculator is available. In case of delays in the commissioning, proposals will be executed with the PI230 and FLASH receivers instead.
• SEPIA can house
  
  • 3 ALMA-type receiver cartridges with dual polarization, sideband-separating mixers (2SB)
    
    • a band 5 receiver, covering 159 to 211 GHz,
      
    • a new band 7 receiver, covering 272 to 376 GHz,
      
    • a band 9 receiver, covering 578 to 738 GHz.
      
  • Only the band 5 receiver is available for Monitoring and Large Programmes.
  • The band 7 receiver is offered conditional to a successful commissioning in Q1 2019, and replaces the SHFI/APEX-2 receiver.
    
  • All receivers use the XFFTS backends, covering 4 GHz IF bandwidth coverage with a gap of 8 GHz between the two sidebands.
  • The band-7 and band-9 receivers may be upgraded to 8 GHz bandwidth in Q1 2019, depending on a successful commissioning.
  • An observing time calculator for all bands is available.
• CHAMP+: This MPIfR PI instrument is not offered since Period 101 due to ongoing re-commissioning activities.
• SHFI was decommissioned in September 2017 and is replaced by SEPIA and nFLASH.