Reference frames project

Standard reference frames

From the begin of VLT science operations, there have been attempts to assemble sets of calibration reference frames, with the motivation to assist the daytime astronomer in the task of assessing the quality of the daytime calibrations. With the ever growing number of instruments and supported modes, it has become more and more urgent to unify these instrument-specific collections.

As an example of what presently exists, have a look at the UVES example (sciops password required).

A recent initiative led by Andreas Kaufer has proposed to unify and maintain these data as part of the DFO web site. This makes sense since we know probably best all the different types of data, and since we then provide QC input to Paranal as part of the shared QC concept.

Some guidelines

The reference frame set should consist, per major instrument mode, of the following items:

a screen shot of a representative raw file (gif or jpg format),
a thumbnail version of the screen shot to be used in the menu table,
a link to its header (stored as .hdr),
a link to the fits file itself (gzipped if this makes sense).

A major instrument mode would be e.g. IMG, LSS, MOS, IFU. More exotic modes like PMOS, IPOL would not qualify for inclusion here, unless PSO asks for them. The modes defined on the statistics page are a good guideline (include DET in IMG).

For each of these modes, there should be a set of frames, defined as the "standard setups". These are e.g. for imaging the most frequently used filters, or the filters defined for Service Mode. For MOS the typical grisms used would make sense etc. It is not necessary to have all possible setups here. For instance, Giraffe has just five or six out of 150 possible standard modes since they all look alike.

The frames also split up by dpr.type (e.g. BIAS, DARK, FLAT, WAVE).

Whether it makes sense to multiply these by all possible CCD modes (binning, windowing, gain, ports) is a matter of economy. Maybe a pragmatic approach is sufficient: if you can't tell just from the screenshot if that frame is 1x1 or 2x2 binned, choose only the 1x1 version for the collection (and maybe mention in a caption that the 2x2 version just looks the same).

Directories

These data go to the following directory structure:

<qc_web_root>/ALL/ref_frames/<INSTRUMENT>/

Under this root you will find fits/ head/ img/ thumb/ products/. All items should be distributed into this structure.

ref_<instrument>.html

This are the main page for hosting all the links per instrument. From there (under the thumbnails) are links either to the screenshots, or in some cases to other html pages which host the screen shot and some additional information. They go to <qc_web_root>/ALL/ref_frames. There are pages for all instruments presently operational. There is also a template page called template.html.

That page must be executable (chmod u+x ). For editing, the ref_<instrument>.html should never be downloaded from the browser but ftp'ed. The reason for that is that it contains a line

which includes the navigation bar. This is a statement executed by the browser. Hence it is sufficient to maintain the navigation bar file centrally (i.e., by me). It is updated automatically on each html page. If you download the file for editing, you still have valid html code but the navigation bar is frozen then (which probably gets unnoticed for a while).

Names

File names are in principal free. PSO people think in ORIGFILE convention so it would be nice to use such names. Extensions are: .fits, .hdr, .jpg or .gif. We don't need ps files.

Screenshots

The screenshots are typically obtained using rtd with the cut levels and zoom factors optimized. There should always be a cross-cut e.g. for assessing exposure levels.

Products

In some cases (e.g. FORSn) there are already links to pipeline products. These could e.g. be master flats, master biasses, dispersion solutions etc. Details need to be discussed.

As a starting point, I have created a Reference Frames web site. Have a look here. This collection is based on what PSO has collected by now. There are some obvious gaps to be filled by us. This should serve as a guideline to what they need and what we should provide.

Last update: January 15, 2004