Eleventh MESSENGER Planetary Data System Release Is the Largest Yet

NASA requires that all of its planetary missions archive their data in the PDS, which provides well-documented, peer-reviewed data to the research community. The latest release of MESSENGER measurements includes raw and calibrated products created from data acquired through September 17, 2013, and advanced products created from data acquired through March 17, 2013.

“Delivery 11 has the largest volume of data — over three terabytes — in a single MESSENGER delivery to date,” notes MESSENGER’s Science Operations Center lead Susan Ensor, of the Johns Hopkins University Applied Physics Laboratory (APL). “The size of MESSENGER’s deliveries will continue to grow as we add new products, continue to archive extended mission orbital data, and deliver final products at the end of the mission.”

This release includes new raw and calibrated data products from the Gamma-Ray Spectrometer (GRS) anti-coincidence shield acquired after an update to the GRS instrument flight software. The update followed the failure in June 2012 of the cryogenic cooler for the germanium detector. With that failure, the GRS could no longer acquire gamma-ray spectra, so the shield was repurposed as a neutron and electron detector. The new products in this delivery include improved neutron spectra from the shield and new high-time-cadence measurements designed to characterize energetic electron events at unprecedented time resolution.

This release includes a new global, three-color map produced with images acquired by MESSENGER’s Mercury Dual Imaging System (MDIS), and, for the first time, image backplanes with latitude and longitude, as well as incidence, emission, and phase angles.

“The global color maps of Mercury are intended to provide a uniform view of the planet’s surface, so differences in lithology and stratigraphy can be analyzed easily,” said APL’s Mary Keller, a remote sensing scientist on the MESSENGER team. “The three-color map uses a subset of the bands that were combined into the eight-color map and provides a higher-resolution view of surface features for comparison.”

Also now available are reflectance spectra and a 750-nm base map derived from data from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Visible and Infrared Spectrograph (VIRS), and an exosphere model derived from the MASCS Ultraviolet and Visible Spectrometer (UVVS).

“VIRS captures many wavelengths of light from a single spot on the surface at a time, creating a spectral profile of the surface as MESSENGER orbits Mercury,” explains APL’s Noam Izenberg, the MASCS Instrument Scientist. “The VIRS sensor on MASCS has accumulated several million individual spectra, enough that the reflectance of the surface can be interpolated to reveal surface brightness details similar to those seen in the MDIS base map. Both of these instruments probe the spectral ‘fingerprint’ of rocks on Mercury’s surface in different ways, enabling scientists to map the compositional and physical variations of surface rocks by observing how light interacts with them.”

An improved-resolution digital elevation model for Mercury’s northern hemisphere has also been made available in this release. “The newest Mercury Laser Altimeter digital elevation model now includes full coverage of the north polar region, an important milestone for the mission,” says APL’s Carolyn Ernst, the instrument sequencer for MLA. “Additionally, this product has substantially higher spatial resolution (500 meters per pixel) than those previously delivered to the PDS and reveals incredible detail, including wrinkle ridges, ghost craters, central peaks, and crater chains.”

The ACT-REACT QuickMap interactive Web interface to MESSENGER data has been updated to incorporate the full coverage of the MDIS and MASCS VIRS orbital data included in this release. QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from http://messenger.jhuapl.edu/the_mission/mosaics.html.

The data for this release are available online at http://pds.nasa.gov/subscription_service/SS-20140307.html, and all of the MESSENGER data archived at the PDS are available at http://pds.nasa.gov. The team will deliver the next mission data set for release by PDS in September.