[fitsbits] FITS standard for spatial planetary data

[Rob Seaman]

Hello Chiara,

I see Steve Allen has replied and this saves me echoing his good points. Additional comments:

> I am a Research Engineer in a French lab involved in Planetary Sciences (surface imagery and spectro-imagery, in particular).

There are key issues in the data format, not just metadata. Do these images typically result from single chip/amplifier detectors? By spectra-imagery do you mean multi-channel spectrophotometry, or something more arcane? The answers to questions like this will inform whether raw and pipeline-reduced data should be formatted as 2-D or 3-D single images, as multiple extensions (MEFs), or possibly as FITS binary tables.

Will any of these data be created onboard the spacecraft? Data compression for space missions may have requirements differing from those that have so far informed FITS tile compression. My suspicion is that the default Rice compression will be highly applicable here since it originally emerged from considerations of space-based data and operations paradigms, but it is possible that the noise regime of your data might drive some edge cases for tile compression.

> As part of the Europlanet H2020 project we want to propose standard FITS keywords for planetary surface observations. We think that using FITS will make easier planetary data processing, as a lot of software and libraries are already available. In addition to that, FITS format is compatible with the standard archiving constraints imposed by PDS (https://pds.nasa.gov/). Today, European missions use different formats and metadata descriptions, making interoperability and reprocessing really difficult.

This sounds very reasonable.

> Starting from Greisen & Calabretta 2002 and Calabretta & Greisen 2002, projected images will be easily described: I will work with people from PDS and PSA for consistent and unique definitions for each planet.

These are good partners to start with.  Are you aware of the PDS workshop series:

	http://www.hou.usra.edu/meetings/planetdata2015/planetdata20151st.shtml

> Spectro-imaging and raw data will need probably a bigger effort…

Indeed. Simplifying operational logistics will be as important as capturing a formal schema.

> I am writing to this list to ask some questions.
> 
> 1) A working group on Planetary Data already exists?

You might contact the Planetary Data Workshop folks.

> 2) If not, is someone in this list interested in following or contributing to this discussion?

I will be interested in FITS metadata (PDS-ready) for NEOs, asteroids and comets. One imagines there will be some amount of overlap.

Presumably some of the metadata will correspond to planet-based timescales and a subgroup of us are embedded with timekeeping, FITS and otherwise.

> 3) Once a draft of a document is ready, to whom do I submit it? What is the procedure for the IAU evaluates and accepts the new definitions?

As Steve says this is evolving, but the correct answer will continue to be a working group of the IAU Data and Documentation Commission, now dubbed C.B2. Several of us on FITSBITS are also on the OC for C.B2 and can help keep your effort moving forward through the vicissitudes of IAU restructuring. 

Rob Seaman
Tucson, AZ