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What's in a Name?

There is some confusion about the exactly what’s stored in the ALCDEF database. It is often referred to as “the asteroid lightcurve database”, which happens to be the long-established name for the real asteroid lightcurve database (LCDB; Warner et al., 2009).

The LCDB stores the results of data analysis, e.g., rotation periods, taxonomic class, spin axis/shape models, and so on. It does not store the original data used to do that analysis.

On the other hand, the ALCDEF database (call it “ALK-def”) stores only raw asteroid time-series photometry.

Simplifying ALCDEF

To upload data from the main ALCDEF page requires that the metadata and data follow the ALCDEF standard. Programs such as MPO Canopus, written by the author, include provisions for writing such files from the original data. However, many other programs do not and there is a wealth of legacy data that might also be uploaded if there were a simpler format.

In mid-2015, the Simple-ALCDEF (S-ALCDEF) standard was introduced. In its simplest form, S-ALCDEF requires only four lines other than the data lines. For example, assuming all the data in the file are for the same asteroid (bold text highlights the four lines),

            #First night

            #Second Night

Lines preceded by the hashtag (#) are ignored. The hashtag can also be embedded in a line. Starting with the hashtag, it and all characters after it on that line are ignored, making it possible to include a comment about a specific line in the file.

More details about S-ALCDEF can be found in the ALCDEF documentation. The S-ALCDEF page is found at

Redundancy! Redundancy!

The ALCDEF and S-ALCDEF standards and MPC web site provide a straight-forward way to archive raw asteroid time-series data that are readily available and critical to researchers. However, the ALCDEF database is far from universally-accepted and used.

For example, all data presented in articles in Astronomy and Astrophysics must be archived in the Centre de Donnée astronoimiques de Stransbourg (Lub, 2015; CDS, Strasbourg Astronomical Data Center). This is not going to change nor should it do so. It’s also unlikely that a researcher is going to prepare his data for more than one archive database, even though in this case there may not be significant differences in the files submitted to CDS and ALCDEF; it might be something for those submitting to CDS (or ALCDEF) to consider.

There are many other repositories of raw data, many on private web sites or in the computer equivalent of “dusty filing cabinets.” It’s hoped that the introduction of S-ALCDEF will encourage even more submissions to the system.

While a single universally-accepted repository is preferable, a minimum number, each with long-term stability that extends beyond those who currently own and/or maintain it, is a good alternative and is encouraged.


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