APEX proposals

Call for proposals

The next Call for proposals will be issued in mid-October with a deadline in mid-November.


​​Previous Call:


Proposals are invited for observations with APEX in the period August – December 2018.


Deadline: Tuesday 15 May 2018 (23:59:59 UTC)


APEX, the Atacama Pathfinder EXperiment, is a 12 m diameter submillimetre telescope at 5100 m altitude on Llano Chajnantor in Chile. The telescope is operated by Onsala Space Observatory, Max-Planck-Institut für Radioastronomie (MPIfR), and European Southern Observatory (ESO).

In order to prepare APEX for continued operation until the end of 2022, the telescope is undergoing major upgrade activities from September 2017 to March/April 2018. Also, as part of the upgrade, the suite of single pixel heterodyne receivers on APEX is being replaced and greatly upgraded in performance so that all bands will be covered by dual polarisation/dual sideband receivers, in many cases also with increased IF bandwidth. As part of this upgrade, SHFI has been decomissioned and the bands it previously covered (roughly ALMA bands 6, 7 and 8) will in future be covered by the new receivers. When fully completed in 2019, the receiver upgrade will provide APEX receivers covering from ALMA Band 5 to Band 10 inclusive. This call covers the second semester of 2018 when the new receiver suite will only be partially complete.

The telescope is expected to resume science operations in April or May 2018, after the completion of the re-commissioning activities. At the time of issuing this Call, the Swedish time slots have not yet been defined.  

The receivers offered in this Call are:

  • the heterodyne receivers:
    • SEPIA (band 5: 159-211 GHz; band 9: 600-722 GHz; band 7 is not offered in this Call)
    • PI230 (band 6: 200-270 GHz)
  • the bolometer arrays:
    • ArTeMiS (350 and 450 μm )
    • LABOCA (870 μm).

The Swedish share of the APEX collaboration is (from 2018) 13%. In general, proposals for Swedish time on APEX must have a PI or at least co-I with Swedish affiliation, but see below for exceptions.

On this page you will find information about:

  • Observing period, operations, etc.
  • Telescope
  • Receivers
  • Proposal preparation and submission
  • Further information and useful links

Observing period, operations, etc.:

This Call for proposals is for Swedish time on APEX in the period August – December 2018 (exact dates are currently not known but it is expected that Swedish observations will be carried out in August and October; see the APEX Science schedule, might not yet be updated).

In general, proposals for Swedish time on APEX must have at least one co-I with a Swedish affiliation; however a maximum of 20% of the observing time will be open to international proposals (i.e. those without a PI or co-I with a Swedish affiliation) - to be scheduled based purely on scientific merit.

Note that before the reduction of Swedish APEX share from 23% to 13%, when Swedish APEX time allocation operated an open skies policy, approximately 50% of all APEX proposals had no Swedish co-I. In the post 2018 period we very strongly encourage collaboration of international users with Swedish astronomers in proposing for Swedish APEX time, which will increase the probability of success for your proposal. Note that projects without Swedish Co-I's can also apply for ESO time on APEX; and it remains possible to submit the same proposal for both Swedish international time and ESO time (note however the earlier deadline for ESO time).

Note that the weather is best during night time and early mornings, which is important to consider for observations at the higher frequencies. Observations of sources closer than 30 degrees from the Sun are not allowed.

Observations will be performed in service mode.

Observers are encouraged to visit APEX to assist in carrying out the service observations. Travel expenses will afterwards be covered by Onsala Space Observatory, through invoicing via the home institute of the observer. Which of the co-authors who are willing to visit APEX should be indicated in the proposal. More information can be given by the Swedish APEX project scientist Per Bergman (per.bergman@chalmers.se).


  • 12 m diameter telescope for mm and sub-mm waves.
  • Location: Llano de Chajnantor, 50 km east of San Pedro de Atacama, northern Chile. Latitude: 23º00'20.8" South, longitude: 67º45'33.0" West. Elevation: 5107 m.


LABOCA is a facility instrument, available for all users. ArTeMiS, SEPIA and PI230 are partner instrument which will be fully available on Swedish time for all users. 
There are protected guaranteed time observations for some instruments (see ESO Guaranteed Time Observations for Period 102), e.g., several sources for the ArTeMiS consortium.
***  ArTeMiS  ***
ArTeMiS is a bolometer array working simultaneously at 350 and 450 μm, developed by CEA Saclay (France). At 350 μm, the field of view is 4.7' x 2.3' and the number of pixels is 2304. Please use the online observing time calculator at the APEX web site for observing time estimates.
Note the protected guaranteed time observations for ARTeMiS (see ESO Guaranteed Time Observations for Period 102).
***  LABOCA  ***
LABOCA is a bolometer array camera for the 870 μm (345 GHz) atmospheric window. It has 295 channels arranged in a hexagonal layout consisting of a centre channel and 9 concentric hexagons. LABOCA is offered conditional on sufficient demand and a successful completion of the re-commissioning activities in the Cassegrain
The APEX beamwidth at this wavelength is 18.6 arcsec (FWHM) and the total field of view of LABOCA is 11.4 arcmin. The array is undersampled on the sky; the separation between channels is twice the beam size (36 arcsec).
The mean point-source sensitivity of the channels is 60 mJy s1/2 (for extended sources, the sensitivity is 100 mJy s1/2). Please use the online observing time calculator at the APEX web site for observing time estimates.
***  SEPIA  ***
The SEPIA instrument is designed to house three ALMA-style receiver cartridges. Cartridges covering ALMA bands 5, 7 and 9 will be installed in SEPIA, but for this period only band 5 and band 9 will be available. Both receivers are dual-polarization sideband-separating (2SB):
- SEPIA Band 5: 159–211 GHz.
- SEPIA Band 9: 600–722 GHz (upgraded from DSB to 2SB mixers).
Spectrometer: All SEPIA receivers use a Fast Fourier Transform Spectrometer (called XFFTS) with 4 GHz IF bandwidth. The spectrometer covers 4 GHz for each polarisation and for each sideband (i.e., 4x4 GHz in total). The central frequencies of the sidebands are separated by 12 GHz, thus there is a gap of 8 GHz between the two bands. The channel separation is 38 kHz or 76 kHz.
The offered observing patterns are on-off observations, raster maps, and on-the-fly (OTF) mapping. The data will be taken in either beam-switching or position switching mode.
Please use the online observing time calculator at the APEX web site for observing time estimates (note the link to the separate on-the-fly mapping calculator).
Technical details for the band 5 receiver can be found in the following publication: Billade, B., et al. “Performance of the First ALMA Band 5 Production Cartridge”, IEEE Trans. Terahertz Science and Technology, Vol. 2, No. 2, March 2012, pp. 208-214. For a technical description of the band 9 receiver, please see the following publication: Baryshev, A. M., et al. "The ALMA Band 9 receiver. Design, construction, characterization and first light", Astronomy & Astrophysics, Vol 577, A12 (February 2015).  
***  PI230  ***
PI230 is a new 230 GHz receiver covering from 200 to 270 GHz and is offered as a replacement of the SHFI/APEX-1 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 2x4 GHz bandwidth. A more detailed description is available in the presentation A-MKID, PI-230, LAsMA - new MPIfR receivers for APEX.
Please use the online observing time calculator at the APEX web site for observing time estimates (note the link to the separate on-the-fly mapping calculator).

Atmospheric transmission:

It is important to consider the atmospheric transmission at the APEX site. The APEX web site provides information on the atmosphere above APEX (see also, e.g., the beta version of the new 2017 atmospheric transmission calculator on that page) and the annual variation of the pwv (precipitable water vapour). This figure on the APEX web site shows the atmospheric transmission for the SEPIA band 9 frequencies: ChajnantorAtm.pdf.

Proposals for Large Programmes:

For the coming semester, Large Programme proposals are NOT invited.

Proposal preparation and submission:

Onsala Space Observatory uses the NorthStar system for preparation and submission of both 20 m telescope and APEX proposals. NorthStar is used by several radio and optical observatories.

In NorthStar, information about applicants, instruments, targets, etc., is to be provided "on-line", and the scientific justification is to be prepared "off-line" and uploaded as a pdf file (also target lists can be uploaded). NorthStar then produces one pdf file with all information. NorthStar includes information on how to use it.

The proposal must contain a proper and concise scientific justification including an explanation for how the requested observing time was calculated, in total no more than two A4 pages long, plus figures and tables if needed (for a total of maximum six pages). Proposers should mention relevant previous observations with Onsala telescopes, and clearly show preliminary results. Observing time estimates should be made using on-line observing time calculators. If observations are for Ph.D. work, this should be stated.

In order to avoid duplicating observations, please check the ESO archive for previous observations.

Please also check the ESO Guaranteed Time Observations for Period 102, in order to avoid conflicts.

Further information and useful links:

Published: Wed 04 Sep 2013. Modified: Thu 06 Sep 2018