This section describes important changes which took place during Period 102 and 103, as well as changes expected to take place during Period 104.

Seeing and Image Quality:

• The seeing information to be provided in Box 3 of the proposal form is the seeing in the V band at zenith. This ensures that the scheduling tool uniformly takes the seeing into account. Service mode users for approved programmes will enter the Image Quality for the airmass and wavelength of interest required for their observations as a constraint during Phase 2. The article by Martinez et al. 2010 (The ESO Messenger 141, 5) "On the Difference between Seeing and Image Quality" describes the meaning of these two quantities and further information can be found on the Observing Conditions webpage.
• The Exposure Time Calculators have been changed accordingly and clearly distinguish between the two quantities, using a slightly modified version of the formula given in the above article. The ETCs also report on the probability to achieve the input seeing conditions and the resulting image quality.

Exposure Time Calculators:

• Exposure Time Calculators: All ETCs are now using a new sky model developed as part of the Austrian in-kind contribution (see Noll et al. 2012, A&A 543, 92, Jones et al. 2013, A&A 560, 91,  and The Cerro Paranal Advanced Sky Model). 
  

Instruments and Facilities

• HARPS: The Laser Frequency Comb has entered regular operations since Period 102. Instructions for its use are provided in the instrument User Manual.
• 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 June and in the fourth quarter of 2019, respectively. The installation of NIRPS is not expected to affect the operation of HARPS in Period 104.
• SOFI and EFOSC2:  Large and Monitoring Programmes with SOFI and EFOSC2 are not offered in Period 104, as the installation and commissioning of SoXS - the Son of X-Shooter - is expected to start during the third quarter of 2020.
• ULTRACAM:
  
  • 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 offered to the ESO community for up to 5% of the observing time at the NTT in Period 104. 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]sheeld.ac.uk), 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 104 GTO target protection webpages.
• The Visitor focus on the 3.6m telescope is not offered during Period 104 due to the installation and commissioning of NIRPS.