This section describes important changes which took place or are expected during the three priods preceding the Period of the call.

UT instruments and facilities

UT1 - Antu

• KMOS:
  
  • KMOS will host public surveys over 3 years, starting in P116. This will reduce the amount of open time available, due to increased pressure on UT1.
• FORS2:
  
  • As of P116, the Imaging (IMG) observations will no longer be accompanied by a standard field observation. The photometric calibration for the broadband filters b_high, v_HIGH, R_SPECIAL, and I_BESS shall be performed using Gaia stars in the field of view, which can be checked by the users using the functionality now available in the ObsPrep. In case that there are no Gaia stars available (~ 10% of pointings), then a standard field observation will be performed by the observatory. Furthermore, for now, for all other filters the observatory will provide STD field observations. Additionally, because of a change in the FORS2 calibration plan, users should also be aware that absolute photometry down to the 3% level is no longer feasible. Furthermore, only extinction values will be possible to compute, using the standard fields or the Gaia stars.

• FLAMES:
  • Fibre 54 on plate 1 has been taken out of service as it got damaged.

UT3 - Melipal

• SPHERE: 
  • 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.

UT4 - Yepun

• MUSE:
  
  • Astronomers are encouraged to use the MUSE Wide Field Mode with Adaptive Optics, because it is more efficient and suitable than non-AO for most science cases. Until now, a large fraction of MUSE observations were taken in Wide Field Mode without Adaptive Optics (NOAO). While the NOAO mode is essential for programmes gathering information over the 582 - 597 nm wavelength which is otherwise blocked by the Na Notch filter, the benefits of AO are many-fold. Not only the operations at the telescope are routine, but importantly seeing is improved in any observing conditions (poor seeing, light cirrus, high wind speed) while proven to be more stable during long exposure times. In case no Natural Guide Star is available, the so-called Tip-Tilt free mode uses the telescope field stabilisation still providing a significant improvement on image quality. As a result, shorter exposure times are required in AO mode to reach equivalent image quality.
• ERIS:
  • ERIS pupil tracking for IFS and standard NIX imaging is offered starting from P116.
• HAWK-I:
  • The HAWK-I calibration plan does no longer include the observation of 2MASS touchstone fields for photometric calibration. If a photometric accuracy < 0.05-0.1 mag is required, users must request special calibrations in their proposals and include this time to the total time request.

Incoherent combined focus

• ESPRESSO:
  • Significant progress have been made to fix long-standing issues of the LFC, and OBs requesting the LFC have been added to the SM queue. The ESPRESSO IOT is still working on improving the LFC performance. The activities performed and status of the LFC will be soon described in the ESPRESSO user manual.

Visitor focus

• The UT1 Nasmyth A focus is not available for Visitor Instruments, due to the installation of the field corrector lens for MOONS.
  
• Potential users of a visitor focus are requested to consult the VLT Visitor Instruments page.

VLTI instruments and facilities

General:

• 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.
• Monitoring Programme proposals on the VLTI-ATs and VLTI-UTs (GPAO-NGS only) are accepted for both GRAVITY and for MATISSE.

VLTI-UTs:

• Only the Natural Guide Star modes of the VLTI-UT Adaptive Optics (GPAO) is offered in P116: the visible mode (NGS_VIS, replacing the former MACAOs) and the infrared mode (NGS_IR, formerly called CIAOs). See the Period 116 VLTI manual for further details.
  

VLTI-ATs:

• 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 116 VLTI manual for further details.
• A new medium configuration A0-B5-D0-G1 replaces the former K0-G2-D0-J3 configuration, improving sky-coverage, baseline-complementarity between configurations and modes offered. However, it prevents observations for declinations higher than 0\deg. For those northern targets, users are advised to use the large configuration instead. The VLTI configurations are described in more detail in the VLTI Configurations Overview  webpage.
  

Instruments

• One VLTI visitor focus (VISITOR 1) is available. 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 GPAO adaptive optics system (NGS_VIS and the off-axis NGS_IR) in Service and Visitor modes.
  • ESO invites proposals with the goal of performing astrometric measurements (see, e.g., the following articles: Gravity collaboration, 2017 A&A 602, A94 and The Messenger 170, 10). Proposers who need help with the preparation of GRAVITY astrometric observations are invited to contact the ESO Helpdesk well in advance of the deadline.
  • For the GRAVITY dual-field wide mode at the limit of system performance, in particular for crowded fields or embedded objects, it is recommended to confirm positions and magnitudes of AO-guide and fringe tracking stars in images with sufficient angular resolution, not relying purely on catalogs. Such images might also be provided as additional finding charts. We are in the process of further characterizing the performance of the GRAVITY-wide mode as a function of separation of the FT star and the atmospheric conditions. Note that the offered maximum separation of 30 arcsec distance may be optimistic unless the weather is excellent and both the FT and SC stars are bright. With more typical conditions, the maximum separation may be somewhat smaller. A performance estimation tool for this mode is currently under development by the JMMC.
• MATISSE is offered on the UTs (supported by the visible GPAO AO system) and on all the ATs configurations in Service and Visitor modes.
  • MATISSE with the UTs is offered with UT/GPAO for natural guide stars in visible light in both standalone and GRA4MAT modes.
    
  • MATISSE is fully available in the GRA4MAT mode with the ATs and UTs, including chopping. The HIGH+ mode is only available with GRA4MAT. The GRA4MAT limiting magnitude at the UTs has been improved to K<11mag for the fringe tracking object.
• PIONIER PIONIER is offered on all ATs configuration in both service and visitor mode. See the overview or overheads pages.
  • The cooling pump of the detector is currently not performing, and the temperature sensor of the detector is not functional. This situation may affects the performance of the instrument. While a spare for the pump has been identified, the temperature sensor problem remains. A direct consequence of the instrument status is that no Large nor Monitoring Programs are offered for Period 114.