Data levels

An exhaustive description of the APIS service can be found in the following paper, published in Astronomy and Computing in press, Arxiv pre-print. A brief description of the available science products and associated caveats is reminded below.

Data levels

The core database relies on HST FUV planetary auroral observations acquired by the STIS and ACS/SBC instruments from 1997 up to now. These consist of about 6000 individual images and spectra, obtained with different instrumental configurations (filters, slit, gratings), for each of which is derived a set of higher level data.

Imaging :

Images are displayed under three levels of data :
- level 1 (original data) : images retrieved from the STSci archive and individually re-calibrated with the most recent calibration files. These "raw" observations are displayed as fits files and jpeg plots, built in the original telescope field-of-view with instrumental units and a linear intensity scale.
- level 2 (processed data) : extracted, rotated and re-centered images displayed in the telescope field-of-view, in a planet-related frame. They are displayed as fits files and pdf, jpeg plots, built with instrumental units and a logarithmic intensity scale. The fits files contain 7 extensions including : the re-centered science image in instrumental units (extension 0), and the associated pixel planetocentric coordinates (extensions 1 to 6 : latitude, local time, zenithal solar angle and zenithal observing angle at the limb altitude, latitude and local time at the auroral peak altitude). Their header contains basic informations on the original observation and valued-added informations such as planetary and relevant spacecraft (Cassini/Galileo) ephemeris (source : IMCCE).
- level 3 (projections) :
— cylindrical projections provided in pdf and jpeg plots, built with physical units and a logarithmic intensity scale. The projections were applied to re-centered images, once a numerical model of background subtracted, and then converted into brightness units (see the note below) with a dedicated projection routine preserving the photon flux of a given emitting surface.
— polar projections provided in pdf and jpeg plots, built as cylindrical projections.

Spectroscopy :

Spectra are displayed under three levels of data :
- level 1 (original data) : first order long-slit (or slitless) STIS 2D spectra retrieved from the STSci archive and individually re-calibrated with the most recent calibration files. They are displayed as fits files and jpeg plots, built in the original HST field-of-view (slit along the y axis, wavelengths along the x axis) with physical units and a linear intensity scale.
- level 2 (processed data) : extracted 2D spectra, including a specific wavelength calibration whenever possible when not provided by STSci. They are displayed as fits files and pdf, jpeg plots, built in the original HST field-of-view with physical units and a linear intensity scale. With respect to the above mentioned paper, a supplementary processing was applied jpeg/pdf plots of small targets (i.e. out of Jupiter/Saturn) : a median spectrum was subtracted to each row of the 2D spectrum, intensities <150nm were divided by 10 in order to facilitate comparison with signal >150nm and a white arrow at the top right now indicates the body northern pole. The fits files only contain the extracted 2D spectrum. Their header contains basic informations on the original observation and valued-added informations such as planetary and relevant spacecraft (Cassini/Galileo) ephemeris (source : IMCCE).
- level 3 (1D spectra) : 1D spectra extracted from level 2 data (not available for slitless observations). Three average 1D spectra were derived from intensity occurrence levels. They are displayed as fits files and pdf, jpeg plots, built with physical units and a linear intensity scale. The header of fits files contain informations similar to those of level 2.