Overheads (valid for P92)

La Silla

Telescope Instrument Action Time (minutes)
3.6m   Preset 5
3.6m   Preset, within a few degrees from previous target 2
3.6m   Focussing 10
  HARPS Fibre automatic redefinition, object centering on fibre, start guiding 1
  HARPS Instrument configuration 0.5
  HARPS Readout+writing image to disk (416 kpx/s speed) 0.38
  HARPS Readout+writing image to disk (104 kpx/s speed) 1.45
  HARPS Minimum time between exposures 0.53
  HARPS Switching between ThAr and Iodine modes 5
  HARPS HARPS/EGGS or HARPS/CES instrument change 1
  HARPS Polarimeter insertion: circular 0.25
  HARPS Polarimeter insertion: linear 0.5
  HARPS Polarimeter insertion: switching linear/circular 0.25
  HARPS Polarimeter rotation 0.2
NTT   Preset 10
  SOFI Imaging ~30% of integration time
  SOFI Spectroscopy ~25% of integration time
  EFOCS2 Readout + writing file to disk: slow, 1x1 2.67
  EFOCS2 Readout + writing file to disk: slow, 2x2 1.33
  EFOCS2 Readout + writing file to disk: normal,1x1 1.17
  EFOCS2 Readout + writing file to disk: normal, 2x2 0.67
  EFOCS2 Readout + writing file to disk: fast, 1x1 0.40
  EFOCS2 Readout + writing file to disk: fast, 2x2 0.17
  EFOCS2 Spectroscopic acquisition:  
  EFOCS2 -: Setup 1
  EFOCS2 -: 2 cycles, see readout above  
  EFOCS2 Spectroscopic acquisition, narrow slit: add 1

Paranal

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

Telescope Instrument Action Time (minutes)
UT1   Preset 6
UT1   Preset (2nd OB and following in a concatenation) 0.67+(target separation in deg)/60
  CRIRES Acquisition without AO 3
  CRIRES Acquisition with AO 5
  CRIRES Read-out 10%-60% of exp. time[1]
  CRIRES Nodding cycle 0.4
  CRIRES Change of wavelength setting 1.5 - 2.5 [1]
  CRIRES Change of derotator position angle 1
  CRIRES Attached wavelength calibration 2.5
  CRIRES Attached lamp flat 2
  FORS2 Acquisition (1 cycle w/o exp. time)[2] 1.5 or 2
  FORS2 Through Slit Image (2 cycles w/o exp. times)[3] 4
  FORS2 Instrument Setup 1
  FORS2 Retarder Plate Setup per PMOS/IPOL OB 1
  FORS2 Read-out 100kHz binned (spectroscopy) 0.7
  FORS2 Read-out 200kHz binned (imaging) 0.5
  KMOS Acquisition, MOSAIC setup 0
  KMOS Acquisition, non-MOSAIC setup, without exposure time, per cycle (2 cycles usually necessary):  
  KMOS - : read-out + writing image to disk 0.10
  KMOS - : interaction + image reconstruction 0.58
  KMOS Acquisition (2nd OB in a concatenation, MOSAIC and non-MOSAIC setups): arms parking and deployment 4
  KMOS Read-out + writing image to disk 0.10
  KMOS Image reconstruction 0.33
  KMOS Offset (dither, i.e. within individual IFUs) 0.15
  KMOS Offset to sky 0.75
UT2   Preset 6
UT2   Preset (2nd OB and following in a concatenation) 0.67+(target separation in deg)/60
  FLAMES Acquisition[4] 9
  FLAMES Instr. Setup GIRAFFE 1
  FLAMES Instr. Setup UVES 1
  FLAMES CCD read-out GIRAFFE 1
  FLAMES CCD read-out UVES 1
  FLAMES Screen Flatfields 7
  FLAMES Plate Configuration[5] 0-20
  UVES Instrument Setup 1
  UVES Acquisition. Bright Point Source 2
  UVES Acquisition. Faint, Extended or Crowded Field 5
  UVES Read-out[6], 1x1, Fast 0.75
  UVES Read-out[6], 2x2, Slow 0.75
  UVES Attached ThAr, Night time 1.5
  UVES Attached Flat, Night time 2
UT3   Preset 6
UT3   Preset (2nd OB and following in a concatenation) 0.67+(target separation in deg)/60
  ISAAC[7] Instrument Setup, Imaging 0.5
  ISAAC Instrument Setup, Spectroscopy (incl. slit check) 7
  ISAAC Telescope Offsetting 0.25
  ISAAC Target Acquisition 1-4
  ISAACHw Read-out (per DIT, imaging) 0.07
  ISAACAl Read-out (per DIT, imaging without chopping)[8] negligible
  ISAACHw Read-out (per DIT, spectroscopy) 0.13
  ISAACAl Read-out (per DIT, spectroscopy without chopping)[9] negligible
  ISAACAl Imaging with chopping 40%[10]
  ISAACAl Spectroscopy with chopping 30%[10]
  ISAAC Night time flat[11] (one on-off pair) 4
  ISAAC Night time arc[11] (one on-off pair) 3
  ISAACAl Burst and FastJitter Modes See the Burst web page
  XSHOOTER Target acquisition 3-5
  XSHOOTER Telescope offsetting 0.25
  XSHOOTER Instrument setup Slit 0.5
  XSHOOTER Delay before start of exposure: UVB 0 sec
  XSHOOTER Delay before start of exposure: VIS 5 sec
  XSHOOTER Delay before start of exposure: NIR 10 sec
  XSHOOTER UVB Read-out[12], 1x1, Slow/Fast 68/16 sec
  XSHOOTER UVB Read-out[12], 1x2, Slow/Fast 34/8 sec
  XSHOOTER UVB Read-out[12], 2x2, Slow/Fast 17/4 sec
  XSHOOTER VIS Read-out[12], 1x1, Slow/Fast 89/21 sec
  XSHOOTER VIS Read-out[12], 1x2, Slow/Fast 45/11 sec
  XSHOOTER VIS Read-out[12], 2x2, Slow/Fast 22/5 sec
  XSHOOTER NIR Read-out (per DIT) 1.46 sec
  VIMOS IMG acquisition + Instrument setup 3
  VIMOS MOS acquisition + Instrument setup 15
  VIMOS IFU acquisition + Instrument setup 10
  VIMOS Read-out IMG,MOS,IFU (4 quadrants) 1
  VIMOS Change of Filter (IMG) 3
  VIMOS Attached screen flat+arc (IFU, MOS)[13] 5-8
UT4   Preset 6
UT4   Preset (2nd OB and following in a concatenation) 0.67+(target separation in deg)/60
  HAWK-I Acquisition and Instrument Setup 1
  HAWK-I Acquisition (Move to Pixel) and Instrument Setup 3
  HAWK-I Telescope offset (large) 0.75
  HAWK-I Telescope offset (small) 0.15
  HAWK-I Read Out (per DIT) 0.03
  HAWK-I Filter Change 0.35
  MUSE Interactive acquisition loop 2
  MUSE SGS loop closure 1.5
  MUSE Detector setup 0.25
  MUSE Detector readout + FITS merging 1.33
  MUSE Each telescope offset 0.25
  MUSE SGS loop closure for large offset 1.5
  MUSE Derotator offset 0.0018/degree
  MUSE Attached flat field calibrations 4.17 + 1.77/flat_field
  MUSE Attached wavelength calibration 3.0 + 1.87/arc (3 arcs needed)
  SINFONI Acquisition no AO 3
  SINFONI Acquisition AO (NGS) 2 + 4*(DIT*NDIT)[14]
  SINFONI Acquisition AO (LGS) 9 + 4*(DIT*NDIT)[14]
  SINFONI Acquisition target (AO and no AO) 4 + 4*(DIT*NDIT)
  SINFONI Instrument setup (per grating change) 2.5
  SINFONI Science exposure read-out (per DIT) 0.07
  SINFONI Detector setup (per DIT x NDIT) 0.3
  NACO see User Manual ---
VLTI      
  AMBER One calibrated visibility CAL-SCI-CAL, LR [15] 15+45*(number of bands)[16]
  AMBER One calibrated visibility CAL-SCI-CAL, MR, HR [15] 30+45*(number of bands)[16]
  AMBER One calibrated visibility SCI-CAL, LR [15] 10+30*(number of bands)[16]
  AMBER One calibrated visibility SCI-CAL, MR, HR [15] 20+30*(number of bands)[16]
  MIDI One calibrated Visibility SCI-CAL [15] 50
  MIDI One calibrated Visibility CAL-SCI-CAL [15] 75
VISTA   Preset 2
VISTA   Preset (2nd OB and following in concatenation) 0.33+ (target separation in deg)/60
  VIRCAM Guide star handling 0.05
  VIRCAM Autoguiding start 0.083
  VIRCAM Active Optics start 0.75
  VIRCAM Filter change 0.35-0.67
  VIRCAM Detector readout 0.03 per DIT
  VIRCAM Writing FITS to disk 0.067
  VIRCAM Pawpring change 0.17
  VIRCAM Jitter offset 0.067
  VIRCAM Micro step 0.067
VST   Preset 2
VST   Offset at template start 0.25
VST   Set rotator position angle (PA) (abs(PA) < 180) PA/120
VST   2nd OB and following in concatenation  
VST   - Preset 0.5+(target separation in deg)/90
VST   - Set Rotator PA (abs(PA_n)+abs(PA_n+1))/120 [17]
  OmegaCAM Guide Star (GS) aquisition 1
  OmegaCAM Acquisition of new Guide Star after offset 1
  OmegaCAM Re-acquisition of same Guide Star after offset [18] 0.08
  OmegaCAM Pick object 0.75
  OmegaCAM Filter exchange between acquisition and 1st science templates:  
  OmegaCAM - different magazine 1.08
  OmegaCAM - same magazine 1.92
  OmegaCAM Filter exchange between science templates:  
  OmegaCAM - different magazine 0.58
  OmegaCAM - same magazine 1.42
  OmegaCAM Detector readout and data writing to disk, last exposure of an OB 0.33
  OmegaCAM Detector readout and data writing to disk, other exposures 0.67
  OmegaCAM Start Active Optics/Image Analysis 3

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


[1] See CRIRES User Manual for more details

[2] Typically one cycle for the target acquisition (exposure time of the acquisition image not included). MXU, MOS, and PMOS: 2 min. LSS,IPOL,ECH: 1.5 min (per cycle). IMG none.

[3] 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.

[4] Includes configuration of UVES fibres, homing the rotator to zero degrees, swapping of the plates, and the acquisition of field; telescope preset, acquisition of the guide star, and start of the active optics are not included and account with additional 6 minutes. 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.

[5] 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.

[6] In a dichroic exposure the CCDs are read out in parallel.

[7] ISAAC refers to both Aladdin and Hawaii, ISAACHw only to Hawaii detector, ISAACAl only to Aladdin detector.

[8] For the Aladdin SW J+Block,H,K and LW low background NB_3.21 and NB_3.28 filters only.

[9] In Medium Resolution (MR) only.

[10] Global overheads in % are used for the LW imaging and spectroscopic chopping templates

[11] When required, see ISAAC P2PP page and the ISAAC User Manual.

[12] Detectors are read sequentially.

[13] Attached flats and arcs are mandatory for IFU.

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

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

[16] With a maximum number of 3 bands per wavelength setting. For each new wavelength setting, a new calibrated visibility has to be obtained.

[17] 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.

[18] 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.