Overheads

Direct links to instruments on UT1, UT2, UT3, UT4, ICCF, VLTI, VISTA, VST.

Telescope/

Combined focus

Instrument Action Time (seconds)
UT1   Preset + GS acquisition + active optics
360
UT1   Preset  + GS acquisition + active optics (2nd OB and following in a concatenation)
(40+target separation in deg)+60
  FORS2 Acquisition IMG/IPOL/LSS (1 loop)
90
  FORS2 Acquisition MOS/MXU/PMOS (1 loop) 120
  FORS2 Through Slit Image (2 loops w/o exp. times)[1] 240
  FORS2 Instrument Setup 30
  FORS2
Collimator exchange
270
  FORS2 Retarder Plate Setup per PMOS/IPOL OB 60
  FORS2 E2V Read-out 100kHz binned (spectroscopy) 39
  FORS2 E2V Read-out 200kHz binned (imaging) 28
  FORS2
E2V Read-out 200kHz unbinned (imaging)
78
  FORS2 MIT Read-out 100kHz binned (spectroscopy) 41
  FORS2 MIT Read-out 200kHz binned (imaging) 31
  FORS2 MIT Read-out 200kHz unbinned (imaging) 62
  KMOS Acquisition, MOSAIC setup 0
  KMOS Acquisition, non-MOSAIC setup, without exposure time, per cycle (2 cycles usually necessary):  
  KMOS - : interaction + image reconstruction 35
  KMOS Acquisition (2nd OB in a concatenation, MOSAIC and non-MOSAIC setups): arms parking and deployment 240
  KMOS Read-out + writing image to disk 6
  KMOS Image reconstruction 20
  KMOS Offset (dither, i.e. within individual IFUs) 9
  KMOS Offset to sky 45
UT2   Preset + GS acquisition + active optics
360
UT2   Preset  + GS acquisition + active optics (2nd OB and following in a concatenation)
(40+target separation in deg)+60
  FLAMES Acquisition[2] 420
  FLAMES Instr. Setup GIRAFFE 60
  FLAMES Instr. Setup UVES 60
  FLAMES CCD read-out GIRAFFE 60
  FLAMES CCD read-out UVES 60
  FLAMES Screen Flatfields 420
  FLAMES Plate Configuration[3] 0-1200
  XSHOOTER Target acquisition (3 loops, incl. telescope offset and AG readout time; excl. AG integration time): direct/blind 49/65
  XSHOOTER Telescope offsetting 15
  XSHOOTER Instrument setup Slit 30
  XSHOOTER Instrument setup IFU 60
  XSHOOTER Delay before start of exposure: UVB 0
  XSHOOTER Delay before start of exposure: VIS 5
  XSHOOTER Delay before start of exposure: NIR 10
  XSHOOTER UVB Read-out[4], 1x1, Slow/Fast 68/16
  XSHOOTER UVB Read-out[4], 1x2, Slow/Fast 34/8
  XSHOOTER UVB Read-out[4], 2x2, Slow/Fast 17/4
  XSHOOTER VIS Read-out[4], 1x1, Slow/Fast 89/21
  XSHOOTER VIS Read-out[4], 1x2, Slow/Fast 45/11
  XSHOOTER VIS Read-out[4], 2x2, Slow/Fast 22/5
  XSHOOTER NIR Read-out (per DIT) 1.46
  XSHOOTER AG camera detector Read-out 1
  UVES Instrument Setup 60
  UVES Acquisition. Bright Point Source 120
  UVES Acquisition. Faint, Extended or Crowded Field 300
  UVES Duty cycle Red arm[5], 1x1, Fast 47
  UVES Duty cycle Red arm[5], 1x2, Fast (VM only) 28
  UVES Duty cycle Red arm[5], 2x2, Slow 52
  UVES Duty cycle Red arm[5], 2x3, Slow (VM only) 39
  UVES Duty cycle Red arm[5], 1x1, Ultra-fast (VM only)
19
  UVES Duty cycle Blue arm[5], 1x1, Fast 46
  UVES Duty cycle Blue arm[5], 1x2, Fast (VM only) 32
  UVES Duty cycle Blue arm[5], 2x2, Slow 48
  UVES Duty cycle Blue arm[5], 2x3, Slow (VM only) 37
  UVES Duty cycle Blue arm[5], 1x1, Ultra-fast (VM only)
22
  UVES Attached ThAr, Night time; set-up dependent, see User Manual Table 4.2
41 to 89
  UVES Attached Flat, Night time; set-up dependent, see User Manual Table 4.2
44 to 190
UT3   Preset + GS acquisition + active optics
360
UT3   Preset  + GS acquisition + active optics (2nd OB and following in a concatenation)
(40+target separation in deg)+60
  SPHERE Acquisition with GoTo template (2nd OB and following in a concatenation)
180
  SPHERE Acquisition with Hopback template (2nd OB and following in a concatenation)
60
  SPHERE Acquisition without coronagraph centering
600
  SPHERE Acquisition with coronagraph centering
900
  SPHERE Flux measurement (incl. exposure)
210
  SPHERE Centering measurement (incl. exposure)
210
  SPHERE IFS observations, per exposure
NDIT*1.7+10
  SPHERE IFS observations, per dithering position
4
  SPHERE IRDIS observations, per exposure
NDIT*0.85+10
  SPHERE IRDIS observations, per dithering position
4
  SPHERE IRDIS_LSS observations, attached wavelength calibration
210
  SPHERE ZIMPOL observations, per exposure, StandardImaging readout mode
NDIT*0.1+3
  SPHERE ZIMPO observations, per exposure, FastPolarimetry readout mode
NDIT*0.1+3
  SPHERE ZIMPOL observations, per exposure, SlowPolarimetry readout mode NDIT*0.1+13
  SPHERE ZIMPOL observations, per polarimetric cycle 2*5
  SPHERE ZIMPOL observations, per dithering position 5
  SPHERE ZIMPOL observations, per number of field angle values 5
  VISIR Target acquisition: normal and burst-mode imaging, blind 120
  VISIR Target acquisition: normal and burst-mode imaging, and coronagraphy, 1 loop, incl. exposure 420
  VISIR Target acquisition: SAM and coronagraphy, 1 loop, incl. exposure 900
  VISIR Target acquisition: spectroscopy (>1 Jy source) 900
  VISIR Target acquisition: spectroscopy (0.2 to 1 Jy source), incl. exposure 1200
  VISIR Chopping and nodding duty cycle losses 50% of exposure time
UT4   Preset + GS acquisition + active optics
360
UT4   Preset  + GS acquisition + active optics (2nd OB and following in a concatenation)
(40+target separation in deg)+60
  HAWK-I Blind acquisition in No AO mode and Instrument Setup 60
  HAWK-I Acquisition (Move to Pixel) in No AO mode and Instrument Setup 180
  HAWK-I Blind acquisition with GRAAL and Instrument Setup 180
  HAWK-I Acquisition (Move to Pixel) with GRAAL and Instrument Setup 300
  HAWK-I Telescope offset (large) 45
  HAWK-I Telescope offset (small) 9
  HAWK-I Read Out (per DIT), normal observation
1.8
  HAWK-I Read Out (per DIT), FastPhot/Burst NXxNYx1.e-06
  HAWK-I Filter Change 21
  HAWK-I Header merging 5
  HAWK-I After exposure overhead 8
  VISIR Target acquisition: normal and burst-mode imaging, blind 120
  VISIR Target acquisition: normal and burst-mode imaging, and coronagraphy, 1 loop, incl. exposure 420
  VISIR Target acquisition: SAM and coronagraphy, 1 loop, incl. exposure 900
  VISIR Target acquisition: spectroscopy (>1 Jy source) 900
  VISIR Target acquisition: spectroscopy (0.2 to 1 Jy source), incl. exposure 1200
  VISIR Chopping and nodding duty cycle losses 50% of exposure time
  MUSE Interactive acquisition loop 18
  MUSE Acquisition: Slow Guiding System loop closure 20
  MUSE Closure of AO loops (all AO modes) 180
  MUSE Detector setup 15
  MUSE Detector readout + file merging 60
  MUSE Intra-exposure detector delay (for multiple exposures) 5
  MUSE Small telescope offset < 2 arcmin 15
  MUSE Large telescope offset > 2 arcmin 45
  MUSE Slow Guiding System closure after offset 10
  MUSE Derotator offset 5+0.11/deg
  MUSE Attached calibration - WFM 20 + 106/flatfield exposure+ 112/arc lamp exposure
  MUSE Attached calibrations - NFM 20 + 162/flat field exposure + 148/arc lamp exposure (at least 1 per lamp - 3 lamps )
  MUSE Return to origin (no offset/small offset/large offset) 0/15/45
ICCF   Preset any UT + GS acquisition + active optics
360
ICCF   Preset  any UT + GS acquisition + active optics (2nd OB and following in a concatenation)
(40+target separation in deg)+60
ICCF
  Additional overheads in 4-UT mode 120
  ESPRESSO Target acquisition in 1-UT mode 45
  ESPRESSO Target acquisition in 4-UT mode
300
  ESPRESSO Instrument setup 30
  ESPRESSO Readout, transfer, wiping; HR11, 1x1_FAST 45
  ESPRESSO Readout, transfer, wiping; HR21, 2x1_SLOW 68
  ESPRESSO Readout, transfer, wiping; UHR11, 1x1_FAST 45
  ESPRESSO Readout, transfer, wiping; MR42, 4x2_SLOW 41
  ESPRESSO Readout, transfer, wiping; MR84, 8x4_SLOW 36
VLTI      
  GRAVITY One calibrated visibility, CAL-SCI [7] 3600
  GRAVITY One calibrated visibility, CAL-SCI-CAL[7] 5400 (requires waiver)
  GRAVITY Swapping template in dual-field observation 300
  MATISSE CAL-SCI LM-band low and medium resolution, no N-band photometry [7] 2400
  MATISSE CAL-SCI L-band high resolution, no N-band photometry [7] 3000
  MATISSE CAL-SCI-CAL LM-band low and medium resolution, no N-band photometry [7] 3600
  MATISSE CAL-SCI-CAL L-band high resolution, no N-band photometry [7] 4500
  MATISSE CAL-SCI LM-band low and medium resolution, with N-band photometry [7] 3600
  MATISSE CAL-SCI L-band high resolution, with N-band photometry [7] 4200
  MATISSE CAL-SCI-CAL LM-band low and medium resolution, with N-band photometry [7] 5400
  MATISSE CAL-SCI-CAL L-band high resolution, with N-band photometry [7] 6300
  PIONIER Hmag -1.0 to 5.0 One calibrated Visibility CAL-SCI-CAL [7] 1800
  PIONIER Hmag -1.0 to 5.0 One calibrated Visibility CAL-SCI-CAL-SCI-CAL [7] 2700
  PIONIER Hmag 5.1 to 6.5 One calibrated Visibility CAL-SCI-CAL [7] 2400
  PIONIER Hmag 5.1 to 6.5 One calibrated Visibility CAL-SCI-CAL-SCI-CAL [7] 3600
  PIONIER Hmag 6.6 to 8.0 One calibrated Visibility CAL-SCI-CAL [7] 3600
  PIONIER Hmag 6.6 to 8.0 One calibrated Visibility CAL-SCI-CAL-SCI-CAL [7] 5400
VISTA   Preset 120
VISTA   Preset (2nd OB and following in concatenation) 20+ target separation in deg
  VIRCAM Guide star handling 3
  VIRCAM Autoguiding start 5
  VIRCAM Active Optics start 45
  VIRCAM Filter change 21-40
  VIRCAM Detector readout 2 per DIT
  VIRCAM Writing FITS to disk 4
  VIRCAM Pawprint change 15
  VIRCAM Jitter offset 8
  VIRCAM Micro step 4
VST   Preset 120
VST   Offset at template start 15
VST   Set rotator position angle (PA) (abs(PA) < 180) PA/2
VST   2nd OB and following in concatenation  
VST   - Preset 30+(target separation in deg)/1.5
VST   - Set Rotator PA (abs(PA_n)+abs(PA_n+1))/2 [8]
  OmegaCAM Guide Star (GS) aquisition 60
  OmegaCAM Acquisition of new Guide Star after offset 60
  OmegaCAM Re-acquisition of same Guide Star after offset [9] 5
  OmegaCAM Pick object for Move to Gap acquisition 45
  OmegaCAM Filter exchange between acquisition and 1st science templates:  
  OmegaCAM - different magazine 65
  OmegaCAM - same magazine 115
  OmegaCAM Filter exchange between science templates:  
  OmegaCAM - different magazine 35
  OmegaCAM - same magazine 85
  OmegaCAM Detector readout and data writing to disk, last exposure of an OB 0
  OmegaCAM Detector readout and data writing to disk, other exposures 40
  OmegaCAM Start Active Optics/Image Analysis 180

Direct links to instruments on UT1, UT2, UT3, UT4, ICCF, VLTI, VISTA, VST.


[1] Through-slit exposures are mandatory for all spectroscopic OBs. Two cycles are typically enough to center the target on the slit (exposure time of the through slit image not included). MXU,MOS,PMOS,LSS,ECH 2.0 min (per cycle), IMG and IPOL none.

[2] Includes configuration of UVES fibres, homing the rotator to zero degrees, swapping of the plates, and the acquisition of field. For ARGUS fast acquisition (VM only), the acquisition overhead is 2 minutes and is calculated assuming that plate 2 is already attached to the telescope.

[3] Plate configuration takes 20 minutes at most (Medusa fibres). This does not translate into additional overheads if the running exposure on the other plate is at least 20 minutes long. Plate configuration overheads have to be added if the exposure time is shorter than 20 minutes.

[4] Detectors are read sequentially.

[5] Duty cycle includes readout, writing image to disk, and detector wiping. In a dichroic exposure the CCDs are read out in parallel: only the longest duty cycle must be taken into account.

[6] Here: DIT and NDIT as required for the AO natural guide star (NGS).

[7] This time includes all telescope and instrument overheads as well as the integration times on the science target and the calibrator.

[8] When switching from OBn to OBn+1 in a concatenation, the overhead for repositioning the rotator is (abs(PA(OBn)) + abs(PA(OBn+1)))/(2 deg/s). I.e. for an OB sequence with PA=90 degrees, the overhead per OB is 90s. PAs > 180 or < -180 are interpreted as modulu 360. E.g. PA=270 implies motion to PA=-90.

[9] The default dither sequence 'diagonal' with N=5 exposures will not require to change the guide star. A larger offset sequence increases the overhead due to the reaquisition of a new guide star. For exposures shorter than 1-2 minutes, observations can be performed without guiding.