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	This page provides documentation about the process behind the PWV monitor.	databases QC1 table ambient_PWV (store PWV); xshooter_telluric (to identify saturated telluric data) dfos tools trendPlotter for updating PWV plots; MIDAS used for calculating equivalent width output used by none upload/download trendPlotter output PWV monitor

PWV monitor (uvstd_getPWV)

Description

This tool emerged from the UVES STD project (investigating the long-term stability information contained in the UVES standard star data; performed by R. Hanuschik and F. Kerber). The tool name uvstd_getPWV goes back to this early implementation. It was realized that the information about telluric absorption is encoded with high resolution and quality in each standard star spectrum, that it could be used to monitor the PWV (precipitable water vapour) content of the atmosphere, and that this procedure could be extended to XSHOOTER spectra. At a later point nightlog entries were included from the Calista PWV fits to dedicated telluric standard stars in the IR (provided by A. Smette).

Since this tool has become an important provider of generally useful information for the mountain (linked as PWV monitor to the HC monitor), this tool is documented here.

Workflow

<instr> = uves or xshooter: PWV is measured

0. The workspace UVES_STD is generated in the giraffe account, as defined in .dfosrc_UVES_STD

1. The tool checks (for the specified date, or for the tool-calculated current date) in the account specified by for pipeline products of the flux and telluric standards (in $DFS_PRODUCT/<raw_type> where the various values for <raw_type> are hard-coded in the tool).

2. These products are copied to the giraffe account. A MIDAS routine $HOME/UVES_STD/progs/measureTell.prg analyzes the products:

• they get normalized (the flux is calculated in two predefined windows around 700 nm, averaged, divided into the spectra)
• the equivalent width of all spectral features in that region is measured (assuming they are telluric only)
• this number is transformed with a curve-of-growth fit into a column density PWV
• a plot of the spectral region is generated (e.g. here)

3. The new results are written into qc1..ambient_PWV, the HC plot updated

As a pre-condition, the selected telluric STD stars need to be feature-free (no solar-type STD stars). For UVES flux standards, this has been checked.

<instr> = crires or visir: PWV is captured from the web page http://www.eso.org/sci/facilities/paranal/sciops/CALISTA/pwv/data/${PWV_YEAR}.html (the linked example is for 2012).

0. The workspace UVES_STD is generated in the giraffe account, as defined in .dfosrc_UVES_STD

1. The tool checks (for the specified date, or for the tool-calculated current date) if new entries exist in the CALISTA page

3. New entries are written into qc1..ambient_PWV, the HC plot updated

How to use

The tool should not be used on any other account since it would generate conflicting input.

The tool help is available with option -h. It is called as a giraffe cronjob in four steps: for crires, visir, xshooter, and uves. The final 'uves' call has the option -u, for updating the HC plots.

Note that the HC plots have the visir data turned off, since they give systematically different, supposedly bad, results.

Installation

Not applicable, only installed and executed on giraffe account.