Special Call for Period 107


Following the suspension of the regular Call for Proposals for ESO Period 107 due to the ongoing COVID-19 pandemic, and as previously announced, ESO is issuing a Special Call (hereafter SC107) for the submission of projects consisting of novel and urgent observations that must be executed during P107 (April 1st - September 30th, 2021).

The spirit of SC107 is to offer ESO's community the opportunity to take the lead on (or to maintain its leadership) on new, important scientific cases, without having to miss out on them because of the pandemic.

SC107 will be open only to:

  • SCTYPE-C: proposals concerning a highly compelling and competitive scientific topic, requiring urgent observations; 
  • SCTYPE-R: proposals of a risky nature, requiring a small amount of observing time to test the feasibility of a programme;
  • SCTYPE-F: proposals asking for follow-up observations of a programme recently conducted from ground-based and/or space telescope facilities, where rapid implementation holds the promise of breakthrough results.

Proposals submitted in response to SC107 should:

  • preferably request no more than 25 hours of total execution time;
  • clearly indicate in the proposal Title field which of the three criteria described above applies (see below);
  • convincingly justify why the observations must be carried out in P107 in the Special Call Justification field.

Due to the considerable amount of time already committed in Period 107 to Large Programmes and other high-priority programmes that could not be executed during Periods 105 and 106, only up to 15% of the time dedicated to science observations in Period 107 will be available through SC107. It is therefore expected that only very highly rated proposals may obtain observing time.

SC107 will be open as of April 1st, 2021. Users will be able to submit proposals any time and only for observations that must be carried out during P107 (April 1st - September 30th, 2021). Requests for Period 108 and subsequent semesters must be submitted through the regular channels, whereas  requests for transient events must be submitted through the DDT channel.

Guidelines for applicants

  • Proposals qualifying for SC107 must be prepared with the p1 proposal submission tool, as for regular cycles. 
  • They must comply to the proposal anonymization rules: proposals violating the requirements will be flagged by the reviewers to ESO for possible disqualification.
  • The applicants must indicate the class to which the proposal belongs.
  • The recommended maximum requested time is 25 hours.
  • The submission of proposals in response to SC107 can take place, initially, any time from April 1st to September 1st, 2021
  • Depending on the evolution of the pandemic and its impact on the operations during Period 107, ESO may decide to extend the Call until the end of the Period (September 30th) or to anticipate the termination of the Call.
  • Given the very significant amount of time carried over from Periods 105 and 106 (which may increase between now and the start of Period 107), the amount of time which ESO will allocate through SC107 is capped to 15% of the total science time during the semester.
  • The requests should be limited to observations to be fully performed within P107. Cases implying a carry-over into P108 (and subsequent semesters) will be considered only under very exceptional circumstances. 
  • In their scientific rationales, the applicants must provide a solid justification as to why the observations have to be executed in P107 and cannot wait for future, less critical Periods. Examples and counter-examples of cases qualifying for SC107 are given below.
  • Proposals for observations of events of transient nature (supernovae, gamma-ray bursts, GW counterparts, solar-system bodies, X-ray binaries, etc) must be submitted via the regular DDT channel for P107.
  • Proposals requiring a very fast reaction time despite of the fact that they are not related to transient phenomena, must make use of time constraints in the p1 proposal submission tool. This will guarantee an automatic flagging of the urgency and a fast-track processing. In the absence of specified time constraints, the proposals will be treated as non-urgent, with a duty-cycle of one to two weeks.
  • Resubmissions of previously rejected proposals (including those submitted for P108) will not be considered. This will also apply to proposals that were approved in previous semesters, but could not be completed because of the Observatory shutdown caused by the pandemic.

Special Call code

To facilitate the proposal distribution and review procedures, the applicants must add the following keyword to the Title section of the proposal:


Where X is a one-character code to be chosen from the following list:

  1. C (for Compelling/Competitive)
  2. R (for Risky)
  3. F (for Follow-up)

For example, if the proposal concerns a highly compelling and competitive scientific topic, the following keyword must be added at the end of the title: 


Example: Spectroscopic confirmation of a quasar at redshift z=30 (SCTYPE-C)

In case the applicants feel their proposal falls under more than one of the three classes, the dominant one must be chosen.

The users can provide additional information on the reasons as to why the proposal is submitted via SC107 in the Special Remarks field of the proposal.

The review process

Observing time will be allocated following the recommendation by a committee of experts external to ESO, grouped in four panels, one for each science category (ABCD). Each panel is composed by six members and a Chair, plus one or more on-call reviewers. The referees were selected among the pool of scientists who already served in the ESO Panels (and are not serving during P108). As in regular cycles, their identity will remain anonymous.

As the SC107 proposal submission and review will partially (but significantly) overlap with the proposal handling procedures for Period 108, the review process was definined and streamlined in such a way that it can run in parallel without interfering with the regular cycle. Here follows a schematic description:

  1. The proposal is submitted by the PI choosing the SC107 cycle and the suitable scientific category (ABCD) in the p1 proposal submission tool;
  2. Upon submission, the proposal undergoes urgency and technical feasiblity assessments by ESO staff on duty at the Observatory. Very urgent cases (i.e. requiring reaction times shorter than 24-48 hours) are flagged immediately to the Director General (or his deputy on duty) for a prompt decision and possible immediate implementation.[*]
  3. The proposal is forwarded only to the members of the panel for the specified science category (ABCD);
  4. The relevant panel members declare possible conflicts of interest. Conflicted members are removed from the rest of the evaluation process. If applicable, the conflicted member/s is/are replaced by the on-call backup/s member/s. The goal is to have each proposal reviewed by at least 3 referees;
  5. In case of conflict, the panel Chair is replaced by the vice-Chair;
  6. All non-conflicted members of the panel review the proposal and send their feedback to the panel Chair;
  7. The referees are given one week to complete the review. The turnaroud (submission to queueing) is expected to be one to two weeks.
  8. The panel Chair leads collects the reviews from the single referees and compiles a final recommendation (approve/reject);
  9. The panel Chair sends the final recommendation to the Director for Science for the final decision (non-conflicted panel members are kept in the loop);
  10. Following the final decision, the panel Chair formulates a feedback comment to be forwarded to the applicants;
  11. The final decision and the panel feedback are passed to the Observing Programmes Office, which informs the applicants.
  12. Cases which are judged not to qualify for SC107 will be rejected upfront.
  13. Proposals concerning transient phenomena will be re-assigned to the regular DDT channel. 
  14. Borderline cases will be discussed by the Chair of the applicable panel and the Chair of the DDT Committee to decide for the most appropriate review channel.

[*]In these cases, following the procedure already in place for urgent DDTs, the data will be embargoed and a final decision on their release taken once the panel has expressed a scientific evaluation.

Director's General Discretionary time (DDT) during P107

During P107 the regular DDT cycle will remain open. However, for this special period only, submissions through this channel will be restricted to proposals targeting objects of a transient nature and not covered by any approved Target of Opportunity programme, requiring immediate observations of a sudden and unexpected astronomical event. The recommended time request for DDTs remains capped to 5 hours.

Science cases falling in this category must be submitted through the DDT channel, and not using SC107. Please note that all the Target of Opportunity (ToO) programmes originally allocated in P105 will be automatically rescheduled in Period 107. These programmes cover a number of transient cases. Before submitting a DDT, please check the list of approved ToO in P105.

Like in all regular semesters, the DDT proposals will be reviewed by the DDT Committee. The DDT and SC107 review processes are completely separated.

Examples and counter-examples


The following fake examples do qualify for SC107.

  1. The discovery of a quasar candidate at redshift 20 by a space-born facility has just been announced. A spectroscopic confirmation from ground-based facilities is required. This is a case with a high scientific impact. Although the target is going to be there for a long time, observations are nevertheless urgent because other large, ground-based facilities will try to secure the data. Missing the case would exclude ESO's community from the competition, potentially depriving it of a very important result.
  2. We have just developed a new technique for mapping the dark matter in the inner regions of galaxies. The tecnique is revolutionary and will lead to high-impact results. A 20 hours test on a selected target will fully demonstrate its power and enable the start of a large programme which was submitted in parallel through the regular P108 cycle. The case is high-risk, high-gain for a comparatively small amount of time. The urgency is justified by two reasons: i) a non-ESO competing group is working on a similar technique; ii) the feasibility needs to be demonstrated before the Large Programmes are reviewed (end of May 2021, i.e. during observing period 107), so that the observing campaign can be started already in P108.


The following fake examples do not qualify for SC107.

  1. A new, extremely bright, core-collapse supernova showing spectral features never seen before was discovered last night. The progenitor has been identified as a 3 Msun star, i.e. well below the canonical 8 Msun threshold for this explosion mechanism. Follow-up observations are urgent, but only because this is a transient object. After making sure there are no Target of Opportunity programmes approved for covering weird SN cases, the applicants should consider submitting the proposal via the regular DDT channel. The same applies to all astrophysical phonomena where urgency is purely related to their transient nature.
  2. In the last years we have assembled a complete photometric catalogue of Blue Wrapping Muon Dwarfs (BWMD) and we now want to characterise them spectroscopically. The catalogue was completed only very recently. The case is urgent, because otherwise we would have to wait another year. The case may be scientifically compelling, but it is definitely not urgent and it can indeed wait for less critical times.

Frequently Asked Questions

  1. Why is ESO issuing a special call for proposals for period 107?
  2. My P105 proposal was rejected by the OPC. Can I resubmit it through SC107?
  3. My P105 proposal was allocated time in the B-rank class and carried over into P107. I fear my observations will not be carried out. Should I resubmit my proposal through SC107?
  4. I have a new science case which I believe it qualifies for SC107, but I am not entirely sure. How should I proceed?
  5. Our science case requires 70 hours of VLT time, but the call says that the recommended requests are capped to 25 hours. Can we submit our proposal nonetheless?

1 Why is ESO issuing a special call for proposals for period 107?

Because of the pandemic, all ESO observing facilities remained closed between March 23 and September 15, 2020. As a consequence, practically the whole Period 105 (April 1st - September 30th 2020) was almost completely lost. As a consequence, it was decided to cancel the Call for Proposals for P107 (April 1st - September 30th 2020) and to carry-over all the P105 allocation into this semester. However, it was felt that ESO's community should not miss new, important and urgent cases that may appear during P107. For this purpose, following a request from Council and after consulting and discussing with the Scientific & Technical Committee and informing the Users Committee, ESO implemented SC107 in addition to the regular DDT cycle. The vast majority of the DDT proposals is about unforeseen transient events. This is the reason why in P107 the DDT channel will collect only those cases, while all other exceptional cases will be submitted through SC107, which is reviewed by a body external to ESO. This was an explicit requirement from Council, in order to guarantee a review process which is as similar as possible to that in place during regular cycles.

2 My P105 proposal was rejected by the OPC. Can I resubmit it through SC107?

No, you should not do that. If your proposal was classified in the B-rank it meants the OPC did not reckon it was a very strong case. Therefore, as such, it does not qualify for SC107, which is meant to enable only exceptional and urgent science cases. You should resubmit it at the next suitable regular deadline.

3 My P105 proposal was allocated time in the B-rank class and carried over into P107. I fear my observations will not be carried out. Should I resubmit my proposal through SC107?

No, you should not do that. You should wait for P107 to be completed and then evaluate the possibility of resubmitting in at the next suitable regular deadline.

4 I have a new science case which I believe it qualifies for SC107, but I am not entirely sure. How should I proceed?

Ask yourself the following questions. If the answer of at least one of them is "yes", then you may have a case.

Is my proposal:

  • new, highly compelling, competitive and urgent?
  • high-risk/high-gain? Will a small time investment potentially enable a very promising proof of concept for the rapid implementation of a full scale, high-impact project?
  • the follow-up of a very recent finding for which a rapid implementation holds the promise of breakthrough results?

In general you should ask yourself why telescope time should be granted to your programme in a semester which is already heavily loaded with highly ranked programmes. The key point is: "Why in P107?". One strong argument is that the proposed project is highly competitive and, if missed, it would prevent ESO's community to acquire crucial data on hot topics, likely to be covered by other facilities.

If your proposal passes these tests, then you may have a convincing case, worth being considered.

5 Our science case requires 70 hours of VLT time, but the Call says that the recommended requests are capped to 25 hours. Can we submit our proposal nonetheless?

Given the limited amount of time during P107, requests larger than 25 hours are discouraged. However, the proposal submission system will not prevent the submission of a larger (but smaller than 100 hours) request, should the science case require it.


Last update: Fri Jan 29 10:39:34 CET 2021

Observing Programmes Office - opo@eso.org


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