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 in the period July–December 2021.

Deadline: Thursday 6 May 2021 (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.

Note: ​
- APEX: Large programme proposals are accepted.
- Onsala 20 m telescopeFrom 2020 onwards, Calls for proposals for the 20 m telescope will be issued only once per yearin the autumn, but the posibility to submit ​proposals for Directors Discretionary Time (DDT)​ at any time remains. Proposals for the 20 m telescope must have at least one co-I with a Chalmers affiliation.​​ 
LOFAR single stationFrom 2020 onwards, there will be no calls for proposals for single station observations with the Swedish LOFAR station in Onsala.


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 telescope

The next Call for proposals for observations with the Onsala 20 m telescope will be issued in the autumn of 2021.

Proposals for Directors Discretionary Time (DDT)​

DDT proposals for observations with the APEX telescope and the Onsala Space Observatory 20 m telescope 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: Thu 01 Apr 2021.