Add first overpass date as attribute to output

[merrittharlan]

A feature I would find incredibly useful (albeit a static one) is appending an attribute to the output that contains the first date(s) in the science orbit that data is available for (if the waterbody is in SWORD/PLD). This way it would be very easy for folks to simply add the SWOT orbital length to those dates, to easily predict future overpass times, and get a sense of the SWOT coverage for that waterbody (e.g., number of overpasses). Predicting these dates ahead of time are helpful for planning fieldwork comparing SWOT measurements to in-situ measurements, and helping out with better understanding multi-sensor fusion-- e.g., how often will we get overlapping SWOT/Landsat/Sentinel observations? We are currently storing this date information locally but having it in hydrocron would help us move towards relying on hydrocron for most if not all of our SWOT data needs.

[torimcd]

Hi @merrittharlan, we were discussing this today and wondering if just knowing when the science orbit started would be sufficient, so that by including that as the start date in a query to hydrocron, whatever the earliest time returned would be the first date for that feature. Would that be sufficient? We could include a page in the documentation describing how to get those dates using Hydrocron for this use case. Otherwise, since this isn't something we can easily pull from the shapefiles it would be a bit complicated for us to calculate and figure out how to add say a flag to indicate that it's the first record.