ESO in-kind Projekt

The purpose of this deliverable is to extend the DR06 project to incorporate the new SM-01 sky model. It will allow a more accurate treatment of lower and upper atmospheric contributions to the spectra, expands the wavelength range for emission spectra to include the optical-NIR regime and aims at measuring the amount of precipitable water vapour (PWV) and other molecules (e.g. CO, CO2, CH4, O3) in the atmosphere. In addition, an investigation on whether other atmospheric parameters resulting from the SM-01 model (e.g. airglow intensity, temperatures in the upper atmosphere, etc.) can be estimated.

The deliverable SM-02 will provide

1. a standalone fitting tool,
2. a GUI,
3. a detailed documentation, including a tutorial for observers, and
4. a web-based service.

The fitting procedure of DR-06 is based on several steps: A standard atmospheric profile is refined by a meteorological model (GDAS profiles provided by the National Oceanic and Atmospheric Administration) and data from the ESO Meteo Monitor. This is subsequently used as first input for an atmospheric radiative transfer code. The resulting synthetic sky spectrum is compared to the observed data and the underlying atmospheric profile is iteratively varied and again used for the radiative transfer codes to achieve a best fit (incorporating mpfit library). In addition, the optimisation of the model spectrum also includes an adaption of the wavelength calibration, the continuum level, and the line profile. Currently, DR-06 only works for sky emission in the MIR regime. SM-02 will expand the fitting procedure to the optical-NIR range by considering further sky model components, e.g. airglow (both, lines and continuum). In this way more atmospheric parameters (e.g. OH, solar activity, rotational / vibrational temperatures, see SM-01) can be fitted and the state of the atmosphere can be described more accurately. The Web service aims at generating synthetic sky spectra for an expert user to determine atmospheric parameters, e.g. PWV, or molecular abundances. By providing an extended general web interface it will be possible to adapt the radiative transfer taking either fits information or user defined input, e.g. airmass, meteo monitor information. The calculations are performed on the server side. For complicated spectra, the response time may reach a critical limit, impeding the process for an interactive user. This response time problem and the resulting server load will be investigated. The first release will be implemented based on a web interface like the exposure time calculators, but providing features, which are typically hidden (e.g. real observing time and conditions). It provides an automatic online equivalent of the current manual fitting  performed by the Paranal Observatory team. In normal operation, this tool will be applied to standard stars and sky spectra. The output of the automated fitting will feed additional columns for the “meteo database”. This is provided to the astronomical as well as to the Earth science community (e.g. as input for improving local Paranal weather forecasts or long term monitoring of greenhouse gases). In the process it will be investigated if the existing ESO pipelines need to be adapted before these tools can be applied. Currently, not all pipelines contain the option to store the subtracted sky. Either this option is made available to the users, or one has to find a way to reconstruct it from the HISTORY in the header of the data products.