Astrogeology Science Center

Coordinates of Named Lunar Features Now Available in LOLA Reference Frame

4 June 2012

In 2012, coordinates of the named features in the lunar portion of the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN) Gazetteer of Planetary Nomenclature were updated. Previous coordinates were based on maps using the Unified Lunar Control Network (ULCN) 2005 coordinate reference frame. The new coordinates are derived from maps made in the Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA) coordinate reference frame. These reference frames are referred to the mean Earth/polar axis reference coordinate system for the Moon. The updated coordinates will facilitate the identification of named lunar features on images derived from LOLA topography. Dots representing the center coordinates of named features should fall in the centers of the features when displayed on any map product based on the LOLA reference frame.

The extents and sizes of named features were also updated; these data are approximate and are intended solely to give the user sufficient information to identify named features and their rough extents. A link to a more precise lunar crater database (now in preparation) by Dr. Nadine Barlow will be provided when available.

This new set of coordinates was derived using ArcMap version 10.0 as a display tool, a lunar hillshade image based on LOLA topography (LDEM_128.jp2, 128 pixels/degree or 237 m/pixel, released December 2011, http://pds-geosciences.wustl.edu/missions/lro/lola.htm), and a LRO Wide Angle Camera (WAC) image mosaic (released November 2011, http://wms.lroc.asu.edu/lroc/global_product/100_mpp_global_bw). Feature boundaries were determined using both images, but the features were aligned to the LOLA hillshade image where there were slight discrepancies.

The lunar portion of the Gazetteer of Planetary Nomenclature web site now displays feature coordinates in the LOLA reference frame. The original coordinates (from unknown sources) and the ULCN 2005 coordinates are retained in the gazetteer and can be viewed by gazetteer users by selecting the desired coordinate set from a dropdown menu on the feature pages. The “Unknown” and ULCN 2005 coordinates are now considered archival and will not be updated with new names or changes to approved names.