Important recent changes regarding La Silla, Paranal and APEX instrumentation and facilities

This section describes important changes which took place during Periods 105 and 106, as well as changes expected to take place during Periods 107 and 108.

Proposal anonymisation:

Period 108 marks the full deployment of the Dual-Anonymous Peer Review (DAPR) for proposals submitted to this Call. Applicants must formulate the scientific rationales of their proposals following the anonymisation rules and examples described in this link, which also gives a detailed description of the DAPR paradigm. While Period 106 was used as a dry run, both to make the community aware of the upcoming implementation of DAPR and to test its practical, procedural and policy aspects, from Period 108 proposal anonymisation is mandatory. Failure to abide by the DAPR rules may be penalised.

The fields Background and Expertise and Data Product Delivery Plan (in the case of Large Programmes) are the only fields of the proposal in which information on the proposing team can be disclosed. These fields will not be included in the material distributed to the referees during the proposal review phase and will only be accessible to them after the ranking phase is completed.

Large Programs:

Large Programmes, those that require 100 hours or more, are accepted for Period 108. Large Programmes can only be submitted in even Periods, i.e., Periods with the proposal submission deadline in March/April. A number of instrument restrictions for Large or Monitoring Programs apply. We refer the reader to Sect. 4.4 in the Call for Proposals Period 108.

La Silla

Instruments and Facilities

  • NIRPS:  the Front End Adaptive Optics and the Back End of the Near Infra-Red Planet  Searcher are expected  to  be  commissioned at  the  3.6-m telescope in Period 108. The installation of NIRPS is not expected to affect the operations of HARPS in Period 108.
  • The installation and commissioning of SoXS - the Son of X-Shooter - are expected to start during Period 109. As a consequence, SoFI is expected to be decommissioned shortly before, either end of Period 108 or during Period 109, and EFOSC2 is expected to be decommissioned at the end of Period 110.
  • Large Programme proposals will be accepted for SoFI during Period 108 only and for EFOSC2 during Periods 108 through 110 only. Users should be aware, however, that these programmes may be terminated ahead of the expected time, depending on progress in the activities with SoXS. This will be reviewed again for Period 110.
    • ULTRACAM is a high-speed imaging photometer designed to study faint astronomical objects at high temporal resolutions. ULTRACAM employs two dichroic beamsplitters and three frame-transfer CCD cameras to provide optical imaging with a field-of-view of 60 and at frame rates of up to 300 Hz simultaneously in the u'g'r', u'g'i' or u'g'z' bands.
    • This PI instrument is o ffered to the ESO community for up to 5% of the observing time at the NTT in Period 108. Large Programmes will not be accepted.
    • Operation of this PI instrument requires the presence of the instrument team, so ULTRACAM programmes will preferentially be scheduled contiguously on periods of several nights. For questions on the instrument and observation strategies, users shall contact the instrument PI, Prof. Vik Dhillon (vik.dhillon[AT], at least two weeks prior to submitting their proposal.
    • The ULTRACAM consortium is committed to support the PIs and observers from the ESO community that have been awarded telescope time with ULTRACAM. The ULTRACAM team will support the execution of the observations and the subsequent data reduction to allow the scienti c exploitation of the data obtained with ULTRACAM.
    • Proposers must check that their planned observations do not duplicate any protected targets speci fied for ULTRACAM in the Period 108 GTO target protection webpages.




Rapid Response Mode (RRM) activation policy:

The RRM policy changed starting in Period 105: on-going observations on any VLT instrument can be interrupted by an RRM triggered on that specific UT, even if the trigger requires a change of focus, unless the relevant programme is specifically protected against an RRM trigger (in case of strictly time-critical programmes). The change will be operational by the start of Period 108 for UT1 and UT2 instruments, and may be ready at UT3 for the start of the Period. It is expected to be operational on UT4 later during period Period 108. More information on the Rapid Response Mode can be found on the Phase 2 page.

UT instruments and facilities

UT1 - Antu

  • KMOS:
    • KMOS is available for Science Operations with 23 arms. No intervention to recover arm #14 is currently planned in Period 108.

UT2 - Kueyen

  • VISIR:
    • The instrument will be mounted to UT2 during P107.

UT3 - Melipal

    • For the star center observations (obs. Type=C), the WAFFLE pattern amplitude in all modes is calculated automatically and should be left as “AUTO” by default.
    • The upgraded CRIRES will be offered to the community in Period 108 with a limited set of modes (see the CRIRES User Manual for more details).
    • In order to balance the allocated time between telescopes, XSHOOTER has been moved to UT3 at the end of Period 104.
    • The convention for acquisition with blind offset from a reference star has been changed to follow the standard used by other VLT instruments. Please be aware of this when preparing your observations. Carry-over OBs with blind offset will have to be modified accordingly.

UT4 - Yepun

  • MUSE:
    • The extension of the GALACSI NFM tip-tilt limiting J-band magnitude to 17 mag is expected to be commissioned in April 2021, and to be available from then on. Details will be available on the news page of MUSE.
    • Since Period 106, the AO supported MUSE Narrow Field Mode (NFM-AO) is offered for Monitoring and Large Programmes.
    • Target of Opportunity proposals are accepted for MUSE in all its modes.

Incoherent combined focus

    • The 4-UT mode is offered in Visitor Mode only. Observations will be scheduled in groups of consecutive nights. Users must request a total time that is an integer multiple of half-nights (corresponding to 4 hours in Period 106), with a minimum duration for each individual observing slot of one half-night.
    • Proposals requesting 4-UT mode must in particular justify its use compared to the 1-UT mode.
    • Monitoring or Large Proposals are accepted for 1-UT mode only.  These observing modes for 4-UT mode are still under consideration and are not accepted.
    • Since P107 ESPRESSO is offered with a 4x2SLOW binning and readout scheme in high-resolution mode. This configuration is suited for science that targets very low S/N while using only one UT.

Visitor focus

  • The UT1 Nasmyth A focus is available for Visitor Instruments.
  • Potential users of a visitor focus are requested to consult the VLT Visitor Instruments page.

VLTI instruments and facilities


  • For new users to VLTI needing assistance to prepare their VLTI proposals, the community supported VLTI Expertise Centres - disseminated throughout Europe - can offer in-depth support. They also offer support for advanced data reduction and interpretation.
  • VLTI+UT operations will not be available for 6 weeks at the beginning of P108 due to the first phase of the recoating of the four UT coudé trains.
  • Monitoring and Large Programme proposals on the VLTI-UTs and VLTI-ATs are accepted for both GRAVITY and PIONIER without restrictions, and for MATISSE for all modes except the HIGH+ spectral setting and the GRA4MAT mode.


  • In Period 108, ESO will continue a scheme to optimise operations for aperture synthesis with the VLTI. This scheme only applies to service mode proposals using ATs with PIONIER, GRAVITY and MATISSE. The reader is referred to the Period 108 VLTI manual for further details.


  • Two VLTI visitor foci are available in Period 108. Potential users are requested to consult the VLTI Visitor Instrument page.
  • GRAVITY is offered on all AT configurations as well as on all four UTs with the visible (MACAO) and infrared (CIAO, off-axis only) adaptive optics system in Service and Visitor modes.
    • The on-axis mode of the IR wavefront sensor CIAO cannot be offered for the time being due to critical problems that were identified during its commissioning.
    • ESO invites proposals with the goal of performing astrometric measurements, a capability of GRAVITY which is still under development (see, e.g., GRAVITY Collaboration 2017 A&A 602, A94). Proposers who wish to use the astrometric capability and contribute to its development are invited to consult the GRAVITY webpage and contact the astrometric team at least two weeks before the proposal deadline.
  • MATISSE is offered in Period 108 on the UTs (supported by the visible MACAO AO system) and on the short, medium and large AT configurations in Service and Visitor modes.
    • MATISSE is available with the GRA4MAT mode with ATs only.
    • The instrument offers the choice of various spectral resolving powers covering either L and/or M-band (depending on the resolving power) and N-band. The HIGH+ mode is only available with the GRA4MAT mode.
    • Monitoring and Large programmes are offered in all settings in Period 108, except for the new HIGH+ spectral setting. Additionally, Large or Monitoring Programmes requesting the GRA4MAT mode will not be accepted.
  • PIONIER is offered on all ATs configuration and UTs + MACAO in both service and visitor mode. The limiting magnitudes of PIONIER have been updated following the improvements thanks to the installation of NAOMI. The execution times have been adapted accordingly. See the overview or overheads pages.

Survey telescopes and instruments


  • Due to the suspension of science operations at Paranal Observatory due to the pandemic, the end of VIRCAM operations has been postponed, and VIRCAM is now offered for Period 108. A large fraction of VIRCAM time in P108 is devoted to allow the completion of the remaining ongoing ESO Public Surveys, as well as Large Programmes. However, some amount of VIRCAM observing time (up to ~40%) is available for normal programmes within the full range of atmospheric conditions. Particularly encouraged are open time proposals requesting any weather conditions (THIN and turbulence category 85% or 100%), and avoiding RA ranges  RA=0-2h, 4h, 7h-10h, as those are allocated with remaining public survey and large programme OBs.
  • Large and Monitoring Programmes are not accepted for VIRCAM in Period 108.


  • Normal and Large proposals are accepted on the VST in Period 108 without restriction on the conditions. PIs should consider that such programmes can run only one semester as the contract between INAF and ESO ends at the end of Period 108. The instrument is not offered for Monitoring proposals. Proposals that waive proprietary rights are encouraged.



Dates for ESO observing time:

The dates for the ESO observing time in Period 108 are foreseen to be from 15 August to 6 September, from 21 October to 2 November, and from 8 to 20 December 2021. Time critical observations should only be requested within these time slots. Users are encouraged to check the latest version of the schedule.

Length of normal programmes:

In order to solicit longer normal programmes for observations that do not require the best weather conditions, the maximum length of normal programmes on nFLASH-230 has been raised to 199 hours that require PWV > 2mm. For any other instrument, the limit remains 99 hours. Any nFLASH-230 programmes requiring 200 hours or more should be requested as Large Programmes.

Monitoring and Large programmes:

Monitoring and Large programmes will be accepted for ARTEMIS, SEPIA,  and nFLASH.