APEX proposals

For information about ​proposals for Directors Discretionary Time (DDT): see the general proposal page​.

Due to the corona virus situation and its effect on observations, the spring Call for Proposals for observations with APEX (Swedish time), the Onsala 20 m telescope, and the Swedish LOFAR station (stand-alone mode) has been cancelled. The next Call for Proposals will be announced after the summer.


Last Call for proposals (deadline 18 October 2019)

Proposals are invited for observations with APEX in the period April – August 2020. 

Deadline: Friday 18 October 2019 (23:59:59 UTC)
(If you are considering submitting close to the deadline, please note that support will only be available during normal office hours.)


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).

The receivers offered in this Call are:

  • the heterodyne receivers:
    • SEPIA (SEPIA180: 159-211 GHz; SEPIA345: 272-376 GHz; SEPIA660: 578-738 GHz)
    • nFLASH (nFLASH230: 200-270 GHz; nFLASH460: 385-500 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 April – August 2020 (the exact dates for the Swedish observations will be published later in the APEX Science schedule).

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 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).

The RadioNet Trans-national Access (TA) programme supports the operation of APEX (Swedish time). PIs of TNA eligible projects will be asked to complete a brief report and questionnaires. More information about the current TNA programme can be found on the RadioNet TA web site​.


  • 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 and nFLASH are facility instruments, available for all users. ArTeMiS and SEPIA 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 105), e.g., several sources for the ArTeMiS consortium and the SEPIA-NOVA 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 105​).
***  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.
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 (ALMA bands 5, 7 and 9)  ***
The SEPIA instrument is designed to house three ALMA-style receiver cartridges, covering ALMA bands 5, 7 and 9. All three receivers are dual-polarization sideband-separating (2SB):
- SEPIA180 (ALMA band 5): 159–211 GHz.
- SEPIA345 (ALMA band 7): 272–376 GHz. SEPIA345 is offered depending on a successful commissioning.
- SEPIA660 (ALMA band 9): 578–738 GHz.

Spectrometer: The SEPIA receivers use a Fast Fourier Transform Spectrometer with an IF bandwidth of 4 GHz (band 5) or 8 GHz (band 7 and 9; 7.85 GHz in practice). The spectrometer covers 4 or 8 GHz for each polarisation and for each sideband (i.e., 4x4 or 4x8 GHz in total). There is a gap of 8 GHz between the two sidebands. The channel separation is 61 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).

Note the protected guaranteed time observations for SEPIA (see ESO Guaranteed Time Observations for Period 105​).
***  nFLASH (ALMA bands 6 and 8)  ***
nFLASH is a new facility instrument, offered depending on a successful commissioning. It contains two receivers, covering (roughly) ALMA bands 6 and 8. Both receivers are dual-polarization sideband-separating (2SB), and can be used simultaneously:
- nFLASH230 (ALMA band 6): 200–270 GHznFLASH230 is offered depending on a successful commissioning.
- nFLASH460 (ALMA band 8): 385–500 GHz. nFLASH460 is offered depending on a successful commissioning.
nFLASH230 has an IF bandwidth coverage of 8 GHz with a gap of 8 GHz between the two sidebands. nFLASH460 has an IF bandwidth coverage of 4 GHz per sideband. 
The spectrometer is the same as for SEPIA (see above). 
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).​

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 and the annual variation of the pwv (precipitable water vapour).

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 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 105, in order to avoid conflicts.

Further information and useful links:


Published: Thu 02 Apr 2020.