On this page, we list the main changes that affected GRAVITY and this web site.

Timeline of instrument status:

The following table (under development) describes the events affecting the quality or the measurement of data obtained with GRAVITY. Its content can be downloaded as a Comma Separated Values file. It is complete as of September 13th, 2020.

The Start Date column indicates when the event took place. Some events cannot be defined by a single instant, but extend over sometimes several days, weeks or months. Operation with the instrument may continue while the event occurs, in which case the Ongoing flag is set. If the event had ended, the Ongoing ? flag is lowered and End Date is given. The Type column indicates the characteristic(s) of the event: Earthquake, Maintenance, Upgrade, Element failure, Intervention, Pipeline installation at QC, Change of nominal values or thresholds, Modification of configuration file of this database, or Other. The Instrument Modes column indicates the affected mode. The column KPI indicates which quality control parameters identified as Key Performance Indicators (i.e., parameters following the most critical quantities) are affected; the column non-KPI indicates which other critical Quality Control parameters are affected. The Calibration Raw Types column indicates the raw types of the affected calibrations. The Calibration Breakpoint flag indicates if calibrations obtained before the event cannot be used for science data obtained after the event or if calibration data obtained after the event cannot be used with science data obtained before the event. The Comment column provides more details. The History column allows one to see possible past information on the entry.

The Quality Control pages for GRAVITY can be accessed through the QC overview page

Instrument announcements:

  • 2023-07: Several issues with the dual-field wide mode were fixed and this allowed to demonstrate successful observations in LOW spectral resolution also for this mode. We therefore expect users will be able to use this setup at phase 2 (OB creation) in P113 to improve the SNR of interferometric observables on targets that do not need higher spectral resolution.
  • 2023-06: Starting with P112, the logic of the acquisition templates for GRAVITY changes: the current templates (GRAVITY_dual_acq and GRAVITY_single_acq) will be replaced by the following new templates: GRAVITY_single_onaxis_acq, GRAVITY_single_offaxis_acq, GRAVITY_dual_onaxis_acq and GRAVITY_dual_offaxis_acq. The template GRAVITY_dual_wide_acq and GRAVITY_dual_acq_dither remain. In addition, the default values for several parameters change, the "Mode of metrology laser" (SEQ.MET.MODE) has a third value "FAINT" and the dual field acquisiton templates include a new keyword "SC object picking strategy" (SEQ.PICKSC). For details see the GRAVITY template manual.
  • 2022-10: The GRAVITY fringe tracker upgrade, started in April 2022, was completed successfully. The upgrade includes new hardware and improved software, enhancing the fringe tracking quality.
  • 2022-09: Starting with phase 2 of P110, it is possible to turn the GRAVITY metrology laser OFF during observations. As the back scattering of the metrology laser onto the science detector is a major noise source in GRAVITY, this option allows to reduce this noise level when observing faint targets. However, with the laser OFF, no phase referencing between the SC and FT is possible. In the single-field off-axis mode, where the target is always faint and no phase referencing between the SC and FT target is needed, the metrology mode is now by default switched OFF.
  • 2022-03: From P110 a new mode, GRAVITY dual-feed wide, will be offered. This mode allows fringe tracking from a target that is up to 30” away from the science target by using the VLTI Star Separators to separate the beams. More information is given on the instrument description page.
  • 2020-11: After a successful re-commissioning, GRAVITY is back in science operations producing science data since November 30th. Fortunately, the science capabilities and accuracy of the instrument have not been affected by the long shut-down.
  • 2020-03: As part of the cease of science operations at Paranal and transition into safe state, GRAVITY has been warmed up and completely shut down. It is expected that GRAVITY will be put back into operations as soon as the observatory resumes operations. The latest new concerning the observatory state can be found at the La Silla Paranal Observatory News page.
  • 2020-01: Unfortunately, CIAO on-axis could not be put in operation for P104. CIAO on-axis will not be operational in P105 either. ESO is studying how to mitigate this unsatisfactory situation, however a solution is not expected in the near future and therefore CIAO on-axis will not be available for the time being.
  • 2019-10: The replacement of the medium and high resolution grisms of GRAVITY in October 2019 went without any problems and the new grisms provide an increase in throughput by a factor of 2.3 and 2.8 respectively. When constructing OBs, the increased sensitivity will have to be taken into acocunt (e.g. to avoid saturation when using old DIT settings).
  • 2019-09: For P105, there are no changes foreseen with respect to what is offered for GRAVITY itself. However a new atmospheric turbulence constraint replaces the current seeing constraint, a new phase 1 proposal preparation and submission tool will have to be used to request observing time, and the way the requested VLTI baselines and VLTI observation types have to be specified has changed.
  • 2019-07: GRAVITY will undergo an intervention in October 2019 during which two grisms in the spectrometer of the science camera will be exchanged. The throughput of these new grisms is about a factor of two higher in comparison with the currently used grisms. GRAVITY will be available for science observations again in November 2019.
  • 2019-03: From P104 on, the limiting magnitudes for the ATs have been increased by 1 magnitude due to NAOMI (see the instrument description page), and there is no longer a constraint on the magnitude difference between the SC and FT object in dual-field mode. Also, CIAO on-axis is offered starting with P104.
  • 2018-08: From P103 on, the lower limit on the separation for dual-field mode has been relaxed. This is achieved by using the beam splitter for targets with small separations, at the disadvantage that the throughput is reduced by a factor of 2.
  • 2018-02: From P102 on, GRAVITY is offered in both Service and Visitor Mode. Furthermore, proposals with the goal of performing astrometric measurements are now welcome, to further develop this capability of GRAVITY. For details, see the P102 User Manual.
  • 2017-09: For P101, GRAVITY is offered with CIAO off-axis Coudé guiding. The limiting magnitudes were also revised: with the ATs, 1m fainter magnitudes are being offered (see the instrument description page).
  • 2017-03: Data tools links listed here.
  • 2017-03: For P100, GRAVITY is now offered for:
    • excellent seeing conditions with fainter limiting magnitudes in single and dual field. See the instrument description page.
    • Large Programs
  • 2016-12: For P99 phase 2 OB preparation, note the change in the acquisition. There are now two separate templates for single-field or dual-field acquisition.
  • 2016-08: For P99, GRAVITY can be requested with both ATs and UTs as feeding telescopes. The instrument can be used as spectro-imager in single field (medium and high spectral resolution) and in dual field (low, medium and high spectral resolution). GRAVITY's astrometric mode and its CIAO units undergo commissioning throughout P99.
  • 2016-03: GRAVITY will be offered for the first time to the community for regular programs in P98 and for Science Verification in P97. The instrument is offered with the auxiliary telescope array in spectro-imaging mode for the medium and high spectral resolution settings. GRAVITY can be used in both single and dual field modes (i.e. both on-axis and off-axis fringe-tracking).

GRAVITY in the news

For the latest highlighted science results, please consult the ESO Press Release page.