Important changes for Period 100:

• ESO strongly encourages programmes that effectively exploit both the best and worst observing conditions on the VLT. Very few proposals request observations that exploit seeing ≤0.5 arcseconds, or precipitable water vapour ≤0.5 mm, and ESO invites the unique science that can be carried out under either set of conditions. At the other extreme, ESO receives very few proposals that can use > 1.2 arcsecond seeing in the V-band, thin-thick clouds and no Moon constraints. These are particularly needed for VIMOS and VISIR; VIMOS is only available for filler proposals with the loosest observing conditions as it is dedicated to ongoing Public Surveys and will likely be decommissioned towards the end of P100.
• The available time on UT4 is limited in Period 100 due to ongoing Adative Optics Facility (AOF) commissioning activities and GTO.
• Due to major maintenance activities, ESO time on APEX is restricted to two timeslots: 27 July – 9 August and 22 September – 1 October 2017.
• Large Programmes are particularly invited for the 3.6-m telescope in Period 100.
• The second generation VLTI instrument, GRAVITY, is offered on both the UTs and the ATs in Period 100 in Service Mode.
• Service Mode observations are encouraged on all VLTI instruments; teams requesting Visitor Mode for VLTI should carefully justify the need for this mode. Furthermore, VLTI will not be available for approximately one month in the second half of P100 for activities related to the installation of MATISSE and the installation and commissioning of NAOMI.
• ULTRACAM is offered on the NTT to the ESO community for up to 5% of the available observing time for the first time in P100. Large Programmes will not be accepted. Proposing teams should contact the instrument PI (Vik Dhillon) well ahead of the proposal submission deadline.