Important changes for Period 101:

• There have been major modifications in the scientific categories A and B, following the recommendations of the Observing Programmes Committee (OPC). Please see the OPC Categories page for more details.
  
• 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 VISIR.
• New Large and Monitoring Programmes are not offered on UT4 in Period 101 due to existing commitments. 
• Large Programmes are particularly invited for HARPS in Period 101.
• VIMOS is not offered in Period 101 as it will be decommissioned at the end of Period 100 or early in Period 101.
• ESO encourages AMBER users to utilise Period 101 to complete ongoing programmes as it will be decommissioned at the end of Period 101 to make space for a visitor focus in the VLTI laboratory.
• MUSE observations are offered for the first time using the adaptive optics module GALACSI in its Ground Layer Adaptive Optics mode (see the MUSE News page). Proposals must provide a reference source identifier for all tip-tilt stars (see the ESOFORM User Manual).
• ESO offers GRAVITY on all AT configurations as well as on the four UTs with the visible (MACAO) and infrared (CIAO in off-axis mode) adaptive optics systems, in Service Mode only. Limiting magnitudes have been updated at both the bright and faint ends. The AT astrometric configuration A0-G1-J2-K0 is officially offered from Period 101 for GRAVITY in Dual-Field mode only (see the baseline configuration webpage). 
• Service Mode observations are encouraged on all VLTI instruments; teams should carefully justify any requests for Visitor Mode on VLTI. VLTI will not be available for approximately three months in Period 101 due to the commissioning of MATISSE and the installation and commissioning of NAOMI.
  
• HARPS: Regular operations with the Laser Frequency Comb are expected to become possible during Period 101. Details regarding its availability and instructions will be provided through the HARPS News page.
  
• ULTRACAM is offered on the NTT to the ESO community for up to 5% of the available observing time in P101. Proposing teams must contact the instrument PI well ahead of the proposal submission deadline. Large Programmes will not be accepted.