Standardized schema for proper motions in reference catalogs

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Details

• Type: RFC
• Status: Implemented
• Resolution: Done
• Component/s:
• Labels:
None
• Location:
This RFC

Description

We will need to apply proper motion corrections (when available) to our reference catalogs when generating astrometric solutions. We have no current standardized schema for these columns. Following suggestions from Paul Price following the lead of Pan-STARRS, I propose the following column names and units.

 pmRa -- Proper motion in the RA coordinate (mas/yr; float32) pmRaErr -- Error in proper motion in the RA coordinate (mas/yr; float32) pmDec -- Proper motion in the Declination coordinate (mas/yr; float32) pmDecErr -- Error in proper motion in the Declination coordinate (mas/yr; float32) epoch -- Mean epoch (TAI MJD for which the position needs no proper motion correction; float64) 

Note that the definitions above allow direct application of the proper motion correction by multiplying pmRa and pmDec by the difference in epoch in units of years. If the angular distance travelled is to be calculated a correction term to pmRa of cos(Dec) is required (or one could do the dot product in Cartesian 3-space).

If pmRaErr or pmDecErr are missing, zero error will be assumed. If any of pmRa, pmDec, or epoch are missing, no proper motion correction will be applied.

People

• Assignee:
Russell Owen
Reporter:
Simon Krughoff
Watchers:
Christopher Waters, Colin Slater, Jim Bosch, John Parejko, Kian-Tat Lim, Paul Price, Robert Lupton, Russell Owen, Simon Krughoff, Tim Jenness