Call for proposals

Observati​ons with APEX and the Onsala 20 m telescope

(For EVN Call for Proposals, see the Astro VLBI page. For LOFAR proposals, see Observing with LOFAR at Astron. For proposals for Directors Discretionary Time (DDT), see below.)

Proposals are invited for observations with the APEX telescope and the Onsala Space Observatory 20 m telescope, in the observing period April–August 2021 (APEX) and January–April 2021 (20 m telescope).

Deadline: Wednesday 18 November 2020 (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.)

Proposals are to be submitted through the NorthStar system.

- LOFAR single station: From 2020 onwards, there will be NO calls for proposals for single station observations with the Swedish LOFAR station in Onsala.​​ 
Onsala 20 m telescope: Proposals for the 20 m telescope must have at least one co-I with a Chalmers affiliation. Calls for proposals for the 20 m telescope will from now on be issued only once per year.


APEX, the Atacama Pathfinder EXperiment, is a 12 m diameter submillimetre telescope at 5100 m altitude on Llano Chajnantor in Chile.

The receivers offered in this Call are the heterodyne receivers SEPIA (SEPIA180: 159-211 GHz; SEPIA345: 272-376 GHz; SEPIA660: 578-738 GHz) and nFLASH (nFLASH230: 200-270 GHz; nFLASH460: 385-500 GHz), and the bolometer array ArTeMiS (350 and 450 μm).

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.

More information about APEX proposals.

Onsala 20 m

The Onsala 20 m diameter telescope in Sweden is equipped with receivers which provide continuou​s frequency coverage in the ranges 18-50, 67-87 and 85-116 GHz with 4 GHz IF bandpass, dual polarisations and full mutual sideband rejection (<−13 dB)If the spectrometer bandwidth is reduced to 2.5 GHz  then in the two high frequency bands both sidebands can be observed simultaneously ("2SB"), with these sidebands having centres 12 GHz apart. 

We welcome proposals for Large programmes, i.e. spanning more than one semester and/or require a large number of hours (>~500 h)​.​

Note: Proposals for the Onsala 20 m telescope must have at least one co-I with a Chalmers affiliation.

More information about Onsala 20 m telescope proposals.

Proposals for Directors Discretionary Time (DDT)​

DDT proposals for observations with the APEX telescope, the Onsala Space Observatory 20 m telescope, and the Swedish LOFAR station in stand-alone mode can be submitted at any time. In general, a DDT proposal requires a special justification of why the project could not be proposed for a regular deadline. A DDT proposal should follow the same format as regular proposals, e.g., the scientific justification should be no more than two A4 pages long, plus figures and tables if needed (for a total of maximum six pages); if only a few hours of observing time are requested, the justification can be shorter. For information about telescopes, instruments, proposal preparation, etc., see links in the left column of this page.​​

All DDT proposals are to be submitted through the NorthStar system. When you have submitted the DDT proposal, please download it in pdf form from NorthStar, and send the pdf file to, and



Calls for proposals for single-dish observations with APEX are normally issued twice per year, with deadlines in April/May and October/November, and for the Onsala 20 m telescope once per year, with deadline in October/November. VLBI-observations are handled through a separate proposal procedure (not by Onsala Space Observatory).


Calls for proposals for observations with some other related instruments can be found here:

The European VLBI Network (EVN) - Using the EVN
> ALMA Science Portal at ESO
> European Southern Observatory (ESO) - Science Users Information
> Low Frequency Array (LOFAR) - Observing with LOFAR 

Note: APEX data can be accessed through the ESO Science Archive APEX Query Form.​​​​​​​​​​​​

Page manager Published: Fri 19 Feb 2021.