APEX: Important recent changes regarding Instrumentation and Facilities

This section describes relevant changes for observations to take place during Period 106.


Proposal anonymisation:

In sight of the future deployment of Dual-Anonymous Peer Review (DAPR), ESO strongly encourages applicants to formulate the scientific rationales of their proposals following the anonymisation rules and examples described in this link, which also gives a detailed description of the DAPR paradigm. Period 106 will be used as a dry run, both to make the community aware of the upcoming implementation of DAPR and to test its practical, procedural and policy aspects. In Period 106, proposal anonymisation will not be mandatory. Nevertheless, applicants should take advantage of the dry run to practice with the new writing style required by the dual-anonymous paradigm, following the guidelines provided in the link above.

p1: A new tool for proposal preparation and submission:

A new tool for the preparation and submission of observing proposals was deployed in Period 105. It represents the first part of a broader re-haul of the ESO Phase 1 system (p1) that also entails a significant modernisation of the Observing Programmes Committee, refereeing process, and related tools. The new p1 system is web-based, resembles the recent p2 tool. Users are encouraged to get familiarised with the new system using the p1demo tool well before the proposal deadline.

Large Programs:

Large Programmes, those that require 100 hours or more, are accepted for Period 106. Since Period 104, Large Programmes can only be submitted in even Periods, i.e., Periods with the proposal submission deadline in March/April. A number of instrument restrictions for Large or Monitoring Programs apply. We refer the reader to Sect. 4.4 in the Call for Proposals Period 106.

APEX upgrade:

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.

Dates for ESO observing time:

The dates for the ESO observing time in Period 106 are foreseen to be from 22 August to 3 September, from 12 to 24 October, and from 4 to 13 December 2020. Time critical observations should only be requested within these time slots. Users are encouraged to check the latest version of the schedule.

ESO share in the APEX collaboration:

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.

Length of normal programmes:

In order to solicit longer normal programmes for observations that do not require the best weather conditions, the maximum length of normal programmes on nFLASH-230 has been raised to 199 hours that require PWV > 2mm. For any other instrument, the limit remains 99 hours. Any nFLASH-230 programmes requiring 200 hours or more should be requested as Large Programmes.

Monitoring and Large programmes:

Monitoring and Large programmes will be accepted for ARTEMIS, SEPIA (SEPIA-180 and SEPIA-660),  and nFLASH-230.



  • ARTEMIS: in Period 106, both the 350 and 450 μm channels are o ffered 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 o ffered in Period 106 depending on a sufficient demand. No Large nor 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 succesful commissioning in Q1 2020. It will contain two receivers replacing the PI230 and FLASH receivers: nFLASH230, covering from 200 to 270 GHz, and nFLASH460, covering from 385 to 500 GHz. Both are dual polarization 2SB receivers, and can only be used independetly in P106. 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 IF bandwidth coverage of 4 GHz per sideband. The backends are digital 4th generation Fourier Transform Spectrometers (dFFTS4G) with 24 GHz bandwidth. An observing time calculator is available.
  • PI230: This 230 GHz receiver is no longer offered in P106.
  • 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 o ffered but observations in this band may be executed with LASMA345 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.
  • CHAMP+: This MPIfR PI instrument is not offered since Period 101 due to ongoing re-commissioning activities.