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


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

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.