Query constraints

The query interfaces can be used to display or to download data according to the query constraints that a user can set on any field. On all query forms, the button “Syntax Help” brings the user to the documentation describing how a query constraint can be formulated. Most typically the user will want to retrieve measurements related to a specific time range; to achieve this, the user must type an interval in the Date field, using the range operator “..” For example: 2016-04-01..2016-05-01 can be used to retrieve the data for the entire month of April 2016.
Use the checkbox on the right of the parameter name to either include or exclude that parameter from the ouput result set.

Output preferences

At the top of any query form the Output preferences panel can be used to set the following properties:

Query parameters common to all Paranal query forms

This section provides information on the common query parameters used in all Paranal ambient query forms.
Date time

The date time (UTC) when the data measurement has started (aka, start time).
To query it is possible to specify a range in date or datetime, or an operator ( < > ) as shown in the examples here below:

  • 2016-04-10..2016-04-12 (for a 2-day interval)
  • 2016-04-10T18:00..2016-04-11T02:00 (for a 8-hour interval)
  • >2016-04-28 (for an open-ended interval)
Integration time

Timespan [s] used for measurement of ambient data sample.

Monitor

Link to the ambient monitor interface. Note that the displayed time interval starts at 21:00 (UTC) on the graph, and that each point on the graph corresponds to the mid-point of the measurement (= start time + 0.5 * integration time).

- More

If you are in tabular mode and you wish to display the full individual record of a matching source, click on the appropriate magnifying glass in the query result page.

 

DIMM Seeing [close]

The Differential Image Motion Monitor (DIMM 2016) channel of the MASS-DIMM instrument (developed by Sternberg Observatory, Moscow, and used for the TMT and E-ELT site surveys) is imaging a single star through two sub-apertures on a CCD. The MASS-DIMM instrument is attached to an 11″Celestron telescope on an ASTELCO NTM500 direct drive mount. It operates in robotic mode on top of a 7m high tower located 100m to the North of UT4. The seeing is defined as the Full Width at Half Maximum (FWHM) of a stellar image at the focus of a telescope observing at 500nm wavelength and at zenith, limited by an atmospheric turbulence with infinite outer scale. The finite nature of the outer scale of the atmospheric turbulence results in an image quality of large telescope actually better than the seeing due to the reduction of the share of atmospheric image motion in the final image size.

Main parameters: seeing, relative flux variations
Time coverage: 2016-APR-04 12:00:00 UTC onwards.
Bibliography: "Combined MASS-DIMM instruments for atmospheric turbulence studies", Kornilov et. al., 2007
Access the Paranal DIMM Seeing query form.

Observation parameters
Target RA and DEC

The right ascension and declination [deg] of the observed star at which the ASM-DIMM telescope measures the site seeing.

Telescope azimuth and elevation

Telescope azimuth and elevation in degrees.

Scientific parameters
DIMM-Seeing

The total seeing calculated with DIMM telescope [arcsec]. The value is calculated using the following formula:
FWHM = 2E(+7) Cn2**(0.6)

Relative Flux RMS

Relative Flux variations measured along the line of sight normalized by the average flux.

Relative Flux RMS base time

Time range of measurements (start of first interval to end of last interval) used to calculate the relative flux variations measured along the line of sight [s].

Engineering parameters
Number of frames

Total number of processed frames.

Airmass

Airmass at which the ASM-DIMM telescope measures the site seeing.

Cn2

Turbulence intensity calculated with both motions [10**(-15)m**(1/3)].

Cn2 Residual

Turbulence intensity calculated with both motions averaged over basetime [10**(-15)m**(1/3)].

Left Mean Flux

Mean total flux in the left image [ADU].

Left Mean Flux RMS

Relative RMS error of total flux in the left image.

Left Scintillation Index

Mean scintillation index in the DIMM aperture for the left image.

Left Strehl Number

Strehl number corrected for seeing for the left image.

Longitudinal Cn2

Turbulence intensity calculated with longitudinal motion [10**(-15)m**(1/3)].

Longitudinal Cn2 Residual

Turbulence intensity calculated with longitudinal motion averaged over basetime [10**(-15)m**(1/3)].

Longitudinal Correlation

Average of the longitudinal basetime correlation coefficient.

Longitudinal Separation

Mean longitudinal separation of right and left images [pixel].

Longitudinal Variance

Average of the longitudinal motion basetime variance [pixel**2].

Longitudinal Variance Average

Low frequency longitudinal motion variance [pixel**2].

Longitudinal Variance RMS

RMS of the longitudinal motion basetime variance [pixel].

Right Mean Flux

Mean total flux in the right image [ADU].

Right Mean Flux RMS

Relative RMS error of total flux in the right image.

Right Scintillation Index

Mean scintillation index in the DIMM aperture for the right image.

Right Strehl Number

Strehl number corrected for seeing for the right image.

Scintillation Index

Mean scintillation index in the DIMM aperture for both images. The value is the average between lsci and rsci.

Transverse Cn2

Turbulence intensity calculated with transverse motion [10**(-15)m**(1/3)].

Transverse Cn2 Residual

Turbulence intensity calculated with transverse motion averaged over basetime [10**(-15)m**(1/3)].

Transverse Correlation

Average of the transverse basetime correlation coefficient.

Transverse Separation

Mean transverse separation of right and left images [pixel].

Transverse Variance

Average of the transverse motion basetime variance [pixel**2].

Transverse Variance Average

Low frequency transversal motion variance [pixel**2].

Transverse Variance RMS

RMS of the transverse motion basetime variance [pixel].

 

 

Historical Ambient [close]

Historical Ambient Data (DIMM3 1998): This interface provide access to the historical Paranal ambient data measured by the old DIMM3 seeing monitor, starting August 1998 and up to the deployment in operations of the new Astronomical Site Monitor (ASM) in April 2016. The ESO seeing monitor (DIMM1) was installed in April 1987, at the northern edge of the summit, and replaced by a more modern copy (DIMM3) in September 1990. Measurements were suspended in July 1991 for the 14 months duration of the levelling work. Seeing has been then monitored during the construction period of the VLT observatory with few interruptions. Finally, DIMM3, upgraded to VLT standards and fully automatized was re-commissioned in August 98 as part of the VLT Astronomical Site Monitor (ASM). The database includes only data starting from August 19th, 1998. All seeing values above 2.5 arcsec have been truncated.

Main parameters: seeing, relative flux variations, wavefront coherence time τ0, isoplanatic angle θ0.
Time coverage: 1998-Aug-19 .. 2016-Apr-04 12:00:00 UTC
Bibliography: "The ESO differential image motion monitor", Sarazin & Roddier, 1990.
Access the Paranal Historical Ambient query form.

Observation parameters
Target RA and DEC

The right ascension and declination [deg] of the observed star at which the ASM-DIMM telescope measures the site seeing.

Scientific parameters
DIMM-Airmass

Airmass at which the ASM-DIMM telescope measures the site seeing.

DIMM-Seeing

Reference observatory site seeing measured by the ASM-DIMM telescope, Full Width Half Maximum at 500nm [arcsec].

Relative flux RMS

Relative Flux variations measured along the line of sight normalized by the average flux.

TAU

Coherence time [s].

THETA0

Isoplanatic angle [arcsec].

 

 

LHATPRO [close]

The Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO's Paranal observatory in support of VLT science operations. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.4 mm). The instrument consists of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (10.5 μm) for cloud detection. Three radiometers (identified by their LHATPRO ID) are currently available at different locations named Platform A, B and C.

Main parameters: IR Temperature at zenith, Liquid Water Path at zenith, and Precipitable Water Vapour at zenith (LHATPRO)
Atmospheric profiles of absolute and relative Humidity, and of Brightness Temperature (LHATPRO profiles)
IR Temperature at target coordinates (LHATPRO IR temperature)
Time coverage: 2014-JAN-01 12:00:00 UTC onwards (LHATPRO ID = 1)
2020-FEB-13 12:00:00 UTC onwards (LHATPRO ID = 2)
2020-FEB-20 12:00:00 UTC onwards (LHATPRO ID = 3)
Bibliography: "All-sky homogeneity of precipitable water vapour over Paranal", Querel & Kerber, 2014.
Access the Paranal LHATPRO, LHATPRO profiles and LHATPRO IR temperature query forms.

As of 2020-Aug-28, some parameters have been updated:

  • the convention for azimuth for all entries in the LHATPRO tables is the same as for ESO telescopes: 0 deg = South, 90 deg = West.
    (LHATPRO, LHATPRO profiles and LHATPRO IR temperature)
  • the RA/DEC coordinates for all entries in the LHATPRO tables are ICRS instead of the apparent coordinates.
    (LHATPRO, LHATPRO profiles and LHATPRO IR temperature)
  • periodic 'peaks' which affected the PWV0 (Precipitable Water Vapour at zenith) since the start of measurements have been corrected; previously, the calculated averages included values obtained while the radiometer was not pointing at zenith.
    (LHATPRO)
  • the Alt/Az and RA/DEC for the profiles of all ingested data now have the correct values; previously, their coordinates were fixed to Alt = 90, Az = 180, with the corresponding RA/DEC (in apparent coordinates).
    (LHATPRO profiles)
  • available profiles back to January 2014 have been ingested. As the algorithm used by the radiometers is sometimes affected by glitches, the following minimum quality criteria must be satisfied for ingestion in the tables: the temperature in all layers must be smaller than 300 K, the temperature in the first layer must be larger than 263 K, the temperature in the 36th layer must be between 215 K and 265 K.
    (LHATPRO profiles)
  • altitude values for all entries in the IRT tables are now forced not to be larger than 90.0 deg, without significant loss of accuracy. Previously, since the IR channel has an independent axis, value slightly larger than 90.0 deg were present.
    (LHATPRO IR temperature)
  • available IRT values for all entries in the IRT tables back to January 2014 have been ingested.
    (LHATPRO IR temperature)

Scientific parameters
Platform

indicates the position where a radiometer is located:
Platform A lat: -24 37 35.95  lon: -70 24 11.93
Platform B lat: -24 37 36.48  lon: -70 24 11.82
Platform C lat: -24 37 36.34  lon: -70 24 12.34
(LHATPRO, LHATPRO profiles and LHATPRO IR temperature)

LHATPRO ID

An integer used to identify a specific radiometer, which could be installed on different platforms, or even sites (e.g. moved from Paranal to Armazones), at different times.
(LHATPRO, LHATPRO profiles and LHATPRO IR temperature)

Telescope azimuth and elevation

Telescope azimuth and elevation [deg] are provided to determine the direction to which the radiometer was pointing at the time of measurement.
As of 2020-Aug-28, the convention for azimuth for all entries in the LHATPRO tables is the same as for ESO telescopes: 0 deg = South, 90 deg = West.
(LHATPRO, LHATPRO profiles and LHATPRO IR temperature)

Target RA/DEC

Right ascension and Declination of the target [deg].
As of 2020-Aug-28, the RA/DEC coordinates for all entries in the LHATPRO tables are ICRS instead of the apparent coordinates.
(LHATPRO, LHATPRO profiles and LHATPRO IR temperature)

IR temperature at Zenith

Measured infrared (10.5 μm) sky brightness temperature at Zenith [Celsius].
(LHATPRO)

IR temperature

Measured infrared (10.5 μm) sky brightness temperature [Celsius].
(LHATPRO IR temperature)

Liquid water path

Measured liquid water path at Zenith [g/m**2].
(LHATPRO)

Precipitable Water Vapour

Measured Precipitable Water Vapor (using the 183 GHz emission line) at zenith [mm].
As of 2020-Aug-28, periodic 'peaks' which affected the PWV0 since the start of measurements have been corrected; previously, the calculated averages included values obtained while the radiometer was not pointing at zenith.
(LHATPRO)

Absolute Humidity

Absolute Humidity Value [g/m**3] measured by a humidity profiler (183-191 GHz) at different heights [m]:
(LHATPRO profiles)

H(0)=0 H(1)=10 H(2)=30 H(3)=50 H(4)=75 H(5)=100 H(6)=125 H(7)=150
H(8)=200 H(9)=250 H(10)=325 H(11)=400 H(12)=475 H(13)=550 H(14)=625 H(15)=700
H(16)=800 H(17)=900 H(18)=1000 H(19)=1150 H(20)=1300 H(21)=1450 H(22)=1600 H(23)=1800
H(24)=2000 H(25)=2200 H(26)=2500 H(27)=2800 H(28)=3100 H(29)=3500 H(30)=3900 H(31)=4400
H(32)=5000 H(33)=5600 H(34)=6200 H(35)=7000 H(36)=8000 H(37)=9000 H(38)=10000

the reference (0m) is the VLT platform.
Relative Humidity

Relative Humidity Value [%] at at different heights [m]. See table above.
(LHATPRO profiles)

Temperature Profile

Brightness Temperature [K] measured by a temperature profiler (51-58 GHz) at different heights [m]. See table above.
As of 2020-Aug-28, available profiles back to January 2014 have been ingested. As the algorithm used by the radiometers is sometimes affected by glitches, the following minimum quality criteria must be satisfied for ingestion in the tables: the temperature in all layers must be smaller than 300 K, the temperature in the first layer must be larger than 263 K, the temperature in the 36th layer must be between 215 and 265 K.
(LHATPRO profiles)

 

 

MASS [close]

The Multi-Aperture Scintillation Sensor (MASS) consists of an off-axis reflecting telescope and a detector unit which measures the scintillations of single stars in four concentric zones of the telescope pupil using photo-multipliers. A statistical analysis of these signals yields information of the vertical profile of the turbulence Cn2(h). It gives the Cn2(h) for 6 layers placed at 0.5, 1, 2, 4, 8 and 16 km above the telescope pupil. The combination of a DIMM and a MASS gives the possibility to measure both seeing and low-resolution turbulence profiles. The provided MASS-DIMM Seeing is in principle more accurate than the DIMM seeing but is only available when MASS produces valid data, i.e. in photometric sky only.

Main parameters: Free atmosphere seeing, MASS-DIMM seeing, coherence time τ0, isoplanatic angle θ0
Time coverage: 2016-APR-04 12:00:00 UTC onwards.
Bibliography: "Combined MASS-DIMM instruments for atmospheric turbulence studies", Kornilov et. al., 2007
Access the Paranal MASS query form.

Scientific parameters
Free Atmosphere Seeing

Free atmosphere seeing at 500nm/zenith from MASS stand-alone integrated profile [arcsec]. MASS-DIMM free atmosphere seeing should be computed from FWHM_FA=2E+7(J_FA)**0.6 with J_FA=SUM(J1:J6).

Free atmosphere is defined to be the portion of the earth's atmosphere in which the effect of the earth's surface friction on the air motion is negligible, and in which the air is usually treated (dynamically) as an ideal fluid.

Free Atmosphere Seeing RMS

Relative RMS of free atmosphere seeing at 500nm/zenith from MASS stand-alone integrated profile.

MASS Tau0

Coherence time (weights method) from MASS stand-alone [s].

MASS Tau0 RMS

Relative RMS on the coherence time (weights method) from MASS stand-alone.

MASS Theta0

Isoplanatic angle from MASS-DIMM integrated profile [J1:J6] [arcsec].

MASS Theta0 RMS

Relative RMS on the isoplanatic angle from MASS-DIMM integrated profile [J1:J6].

MASS Turb Altitude

Characteristic altitude of the free atmosphere turbulence from MASS-DIMM integrated profile [J1:J6] [m].

MASS Turb Altitude RMS

Relative RMS on the characteristic altitude of the turbulence in MASS-DIMM integrated profile [J1:J6].

MASS-DIMM Cn2 fraction at ground

Fraction of turbulence in the ground layer (GL defined as J0, or DIMM minus MASS): FracGL = J0/sum(J0:J6).

MASS-DIMM Seeing

Whole atmosphere seeing at 500nm/zenith from MASS-DIMM combined profile [J0:J6] [arcsec].

MASS-DIMM Tau0

Coherence time of the turbulence in the whole atmosphere from MASS-DIMM combined profile [J0:J6] [s].

MASS-DIMM Theta0

Isoplanatic angle of the turbulence in the whole atmosphere [arcsec].

MASS-DIMM Turb Altitude

Characteristic altitude of the turbulence in the whole atmosphere from MASS-DIMM combined profile [m].

MASS-DIMM Turb Velocity

Characteristic velocity of the turbulence in the whole atmosphere from MASS-DIMM combined profile [m/s].

Engineering parameters
Airmass

Airmass of observed star.

Average Flux

Average flux in aperture A,B,C and D respectively [counts/ms].

Average Flux RMS

Relative rms on the average flux in aperture A,B,C and D respectively.

Average norm of residual

Value of averaged norm of residual.

Cn2

Turbulence intensity from MASS stand-alone integrated profile [10**(-15)m**(1/3)]. MASS-DIMM free atmosphere turbulence intensity should be computed from J_FA =SUM(J1:J6).

Cn2 RMS

Relative RMS on the turbulence intensity from MASS stand-alone integrated profile.

DESI Tau0

Coherence time (DESI method) from MASS integrated profile [s].

DESI Tau0 RMS

Relative RMS on the coherence time (DESI method) from MASS integrated profile.

MASS-DIMM
Layer Cn2

Turbulence intensity J1:J6 in MASS-DIMM layer 1-2-3-4-5-6 respectively [10**(-15)m**(1/3)].

MASS-DIMM
Layer Cn2 RMS

RMS on the turbulence intensity in MASS-DIMM layer 1-2-3-4-5-6 respectively [10**(-15)m**(1/3)].

MASS-DIMM
Layer Height

Position above ground of the maximum sensitivity in MASS-DIMM layer 1-2-3-4-5-6 respectively [m].

MASS-DIMM
Layer 0 Cn2

Turbulence intensity J0 in MASS-DIMM layer 0 (Ground layer: DIMM minus MASS) [10**(-15)m**(1/3)].

MASS-DIMM
Layer 0 Cn2 RMS

RMS of the turbulence intensity J0 in MASS-DIMM layer 0 [10**(-15)m**(1/3)].

MASS-DIMM
Layer 0 Height

Altitude for layer provided by DIMM. The value is only present if the MASS data have been processed together with DIMM data. If present the value is always 0 (m).

Number of layers

Number of nodes of the grid of altitudes, in ESO configuration the number of nodes is set to 6. Additional node on the grid at altitude of 0 km is added when DIMM data are used.

Scintillation index

Index of scintillation in aperture A,B,C,D,AB,AC,AD,BC,BD and CD.

Scintillation index RMS

Relative rms on the index of scintillation in aperture A,B,C,D,AB,AC,AD,BC,BD and CD.

Second altitude moment

Second altitude moment from MASS integrated profile [m**7/3].

Second altitude moment RMS

Relative RMS on the second altitude moment from MASS integrated profile.

 

 

METEO [close]

The Vaisala METEOrological station was installed in Paranal in October 1984 and upgraded in June 1998. It includes, on a 30 m high mast, a number of sensors. The following measurements are provided: Wind speed and direction, Temperature, Humidity, Particle Count at different levels. The meteorological stations compute and store average, root mean square and extrema of each parameter during a preset averaging period (20 minutes). The sampling intervals are 2 seconds for digital sensors (wind speed and direction) and one minute for analog sensors (Temperature, Humidity).

Main parameters: Wind speed and direction, Temperature, Humidity, Particle Count at different levels.
Time coverage: August 1998 onwards.
Access the Paranal METEO query form.

Scientific parameters
Air Pressure

Temporal (1 minute) mean of observatory site ambient baromeric air pressure measured at ground during measurement period [hPa].

Ambient Temperature

Temporal (1 minute) mean of site ambient temperature measured at 30m, 2m, ground and 20m below VLT platform [deg Celsius].

Dew Temperature

Temporal (1 minute) mean of observatory site ambient dew temperature measured at sensor position 30m, 2m, and 20m below VLT platform during measurement period [deg Celsius].

Large (5 micron) dust Particles

Temporal (20 minutes) mean of observatory site ambient large (5 micron size) dust particle count per cubic meter measured at sensor position 20 m and 10 during measurement period [m**(-3)].

Normalised Air Pressure

1 minute average pressure normalised to sea level [hPa].

Rain intensity

1 minute average rain percentage measured at 20m below VLT platform [%].

Relative Humidity

Temporal (1 minute) mean of observatory site ambient relative humidity measured at sensor position 30m, 2m and 20m below VLT platform during measurement period [%].

Small (0.5 micron) dust Particles

Temporal (20 minutes) mean of observatory site small (0.5 micron size) dust particule count per cube meter measured at sensor position 20m and 10m during measurement period [m**(-3)].

Wind Direction (0/360)

1 minute average wind direction at 30m and 10m above ground counted clockwise from North (standard) [deg].

Wind Direction (180/-180)

1 minute average wind direction at 30m and 10m above ground counted clockwise from North (with 180 degree negative offset for display purposes) [deg].

Wind Speed

1 minute average wind speed at sensor position 30m and 10m [m/s].

Wind Speed component U

Temporal (1 minute) mean of observatory site ambient wind speed U vector component, where U is horizontal and points to 330 degree measured at sensor position 20m during measurement period [m/s].

Wind Speed component V

Temporal (1 minute) mean of observatory site ambient wind speed V vector component, where V is horizontal and points to 240 degree measured at sensor position 20m during measurement period [m/s].

Wind Speed component W

Temporal (1 minute) mean of observatory site ambient wind speed W vector component, where W is vertically pointing upwards, measured at sensor position 20m during measurement period [m/s].

Engineering parameters
Air Pressure 3h trend

Surface pressure trend over 3 hours [hPa].

Air Pressure instantanous

Surface pressure at the end of the averaging period [hPa].

Air Pressure max

1 minute maximum surface pressure [hPa].

Air Pressure min

1 minute minimum surface pressure [hPa].

Air Pressure RMS

1 minute RMS surface pressure variation [hPa].

Air Pressure Normalised instantanous

Pressure normalized to sea level at the end of the averaging period [hPa].

Air Pressure Normalised max

1 minute maximum pressure normalized to sea level [hPa].

Air Pressure Normalised min

1 minute minimum pressure normalized to sea level [hPa].

Air Pressure Normalised RMS

1 minute RMS pressure normalized to sea level [hPa].

Air Temperature Instantanous

1 minute air temperature at 30m, 2m, ground and 20m below VLT platform measured at the end of the averaging period [deg Celsius].

Air Temperature max

1 minute maximum air temperature at 30m, 2m, ground and 20m below VLT platform [deg Celsius].

Air Temperature min

1 minute minimum air temperature at 30m, 2m, ground and 20m below VLT platform [deg Celsius].

Air Temperature RMS

1 minute RMS air temperature variation at 30m, 2m, ground and 20m below VLT platform below VLT platform [deg Celsius].

Dew Temperature instantanous

1 minute dew temperature at 30m, 2m and 20m below VLT platform measured at the end of the averaging period [deg Celsius].

Dew Temperature max

1 minute maximum dew temperature at 30m, 2m and 20m below VLT platform [deg Celsius].

Dew Temperature min

1 minute minimum dew temperature at 30m, 2m and 20m below VLT platform [deg Celsius].

Dew Temperature RMS

1 minute RMS dew temperature at 30m, 2m and 20m below VLT platform [deg Celsius].

Humidity instantanous

1 minute relative humidity measured at 30m, 2m and 20m below VLT platform at the end of the averaging period [%].

Humidity max

1 minute maximum relative humidity measured at 30m, 2m and 20m below VLT platform [%].

Humidity min

1 minute minimum relative humidity measured at 30m, 2m and 20m below VLT platform [%].

Humidity RMS

1 minute RMS relative humidity measured at 30m, 2m and 20m below VLT platform [%].

Particle (Large) count instantaneous

Large (5 micron) dust particle count at 20m and 10m above ground at the end of the averaging period [m**(-3)].

Particle (Large) count max

20 minute maximum large (5 micron) dust particle count at 20m and 10m above ground [m**(-3)].

Particle (Large) count min

20 minute minimum large (5 micron) dust particle count at 20m and 10m above ground [m**(-3)].

Particle (Large) count RMS

20 minute RMS large (5 micron) dust particle count at 20m and 10m above ground [m**(-3)].

Particle (Small) count instantaneous

Small (0.5 micron) dust particle count at 20m and 10m above ground at the end of the averaging period [m**(-3)].

Particle (Small) count max

20 minute maximum small (0.5 micron) dust particle count at 20m and 10m above ground [m**(-3)].

Particle (Small) count min

20 minute minimum small (0.5 micron) dust particle count at 20m and 10m above ground [m**(-3)].

Particle (Small) count RMS

20 minute RMS small (0.5 micron) dust particle count at 20m and 10m above ground [m**(-3)].

Rain Intensity instantanous

Rain percentage 20m below VLT platform at the end of the averaging period [%].

Rain Intensity max

1 minute maximum rain percentage 20m below VLT platform [%].

Rain Intensity min

1 minute minimum rain percentage 20m below VLT platform [%].

Rain Intensity RMS

1 minute RMS rain percentage 20m below VLT platform [%].

Wind Direction instantanous

Wind direction at 30m and 10m above ground at the end of the averaging period [deg].

Wind Direction max

1 minute maximum wind direction at 30m and 10m above ground [deg].

Wind Direction min

1 minute minimum wind direction at 30m and 10m above ground [deg].

Wind Direction RMS

1 minute RMS air wind direction at 30m and 10m above ground [deg].

Wind Speed component U instantaneous

Horizontal wind speed U component (into 330 degree) at 20m above ground at the end of the averaging period [m/s].

Wind Speed component U max

1 minute maximum horizontal wind speed U component (into 330 degree) at 20m above ground [m/s].

Wind Speed component U min

1 minute minimum horizontal wind speed U component (into 330 degree) at 20m above ground [m/s].

Wind Speed component U RMS

1 minute RMS horizontal wind speed U component (into 330 degree) at 20m above ground [m/s].

Wind Speed component V instantaneous

Horizontal wind speed V component (into 240 degree) at 20m above ground at the end of the averaging period [m/s].

Wind Speed component V max

1 minute maximum horizontal wind speed V component (into 240 degree) at 20m above ground [m/s].

Wind Speed component V min

1 minute minimum horizontal wind speed V component (into 240 degree) at 20m above ground [m/s].

Wind Speed component V RMS

1 minute RMS horizontal wind speed V component (into 240 degree) at 20m above ground [m/s].

Wind Speed component W instantaneous

Vertical wind speed W component at 20m above ground at the end of the averaging period [m/s].

Wind Speed component W max

1 minute maximum vertical wind speed W component at 20m above ground [m/s].

Wind Speed component W min

1 minute minimum vertical wind speed W component at 20m above ground [m/s].

Wind Speed component W RMS

1 minute RMS vertical wind speed W component at 20m above ground [m/s].

Wind Speed instantanous

Wind speed at 30m and 10m above ground at the end of the averaging period [m/s].

Wind Speed max

1 minute maximum wind speed at 30m and 10m above ground [m/s].

Wind Speed min

1 minute minimum wind speed at 30m and 10m above ground [m/s].

Wind Speed RMS

1 minute RMS wind speed at 30m and 10m above ground [m/s].

 

 

SLODAR [close]

The SLOpe Detection And Ranging (SLODAR) is an optical crossed-beams method for turbulence ranging, based on the Shack-Hartmann wavefront sensor. The instrument, developed by Durham University and ESO, has been operating in robotic mode at Paranal since March 2011. It uses an optical triangulation method for the measurement of the atmospheric turbulence profile. The profile is determined from the spatial covariance of the slope of the wavefront phase aberration at the ground for the two different paths through the atmosphere defined by a double star target. It gives the Cn2(h) for 8 layers starting from the ground with a resolution that varies between 50 and 100 meters depending on the separation of the observed binary system and its zenithal distance. The instrument is optimised to measure the vertical profile of the surface layer of turbulence, in the first 100m above the site. The data is relevant to modelling and understanding the imaging performance of the VLT, both with and without adaptive optical correction.

Main parameters: integrated Cn2 turbulence intensity above unit telescopes
Time coverage: 2016-APR-04 12:00:00 UTC onwards.
More Information: SLODAR pages at Durham University
Access the Paranal SLODAR query form.

Scientific parameters
Cn2 above UTs

Integrated Cn2 above the equivalent UT (VLT Unit Telescope) height [10**(-15)m**(1/3)]

The equivalent UT height is the lower limit of the surface layer which is seen from a UT: currently set at 10m, it will be adjusted to AOF results in the future.
Cn2 fractions

Cn2 fraction below 300m and 500m respectively.

Ratio of the Cn2 integrated from the UT height up to 300m (resp. 500) to <Cn2 above UT>

Surface layer profile

High resolution surface layer fit strength [10**(-15)m**(1/3)].

The result of an exponential model fit with 5m scale height and scaled in strength according to the value of the first SLODAR bin. The integration range is from the SLODAR aperture (2m above ground) up to infinity - in practice the exponential model drops to zero after a few tens of metres.

Engineering parameters
Airmass

SLODAR Airmass.

Cn2 layer thickness

Vertical distance between layers [m].

Cn2 Max Height

Maximum height profiled by this measurement [m].

Cn2 profile in each layer

Turbulence profile Cn2 in layer 1,2,3,4,5,6,7 and 8 respectively, [10**(-15)m**(1/3)].

Cn2 Unresolved

Unresolved turbulence profile Cn2 [10**(-15)m**(1/3)].

Flux

Flux for star 1 and star 2 respectively, [ADU]

Flux Variance

Flux variance for star 1 and star 2 respectively, [ADU**2].

Kolmogorov criterium

Power law exponent of power spectrum density (11/3 = Kolmogorov turbulence).

Data taken in clearly non-Kolmogorov conditions (<0.4) are not validated.

Noise fraction

Centroide noise fraction for star 1 and star 2 respectively, [pixel**2].

Seeing

SLODAR Seeing at zenith [arcsec].

Target name

SLODAR target name.

Telescope azimuth and elevation

Telescope azimuth and elevation [deg].