Bolometric Hemispherical Albedo Map of Pluto from New Horizons Observations
                                                                              
Data Set Overview                                                             
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The NASA New Horizons encounter with the Pluto system in 2015 revealed Pluto to
have an extraordinary range of surface albedos, abundant volatile and refractory
ices, and complex geology from endogenous and exogenous processes (Stern et al.,
2015). Pluto is an active world with ongoing convective and glacial resurfacing,
seasonal volatile transport that includes nitrogen and methane cycles, and
chemical processing by ionizing radiation (e.g., Gladstone et al., 2016; Grundy
et al., 2016; Moore et al., 2016). Photometric properties of a surface,
including albedo, are useful for constraining volatile transport by quantifying
absorbed solar energy, as well as for providing insights into surface processes.
For example, albedo measurements can contribute to relative estimates of
processing, mixing, temporal variability, and age for different terrains.

This dataset is a map of Pluto's incidence-angle-average bolometric
hemispherical albedo. Hemispherical albedo is the ratio of total power scattered
by a surface, where total refers to integration over all emission angles, to
incident power. Bolometric hemispherical albedo is the flux-weighted,
wavelength-integrated ratio and is crucial for understanding the thermal behavior
of a surface. The map was produced using the best-fit lunar-Lambert photometric
functions for Pluto's extreme dark and bright terrains, Cthulhu and Sputnik
Planitia (some names are informal), as representative of low and high
reflectance regions and by approximating intermediate reflectance regions as a
linear combination of these two extremes. New Horizons Long Range Reconnaissance
Imager (LORRI) panchromatic and Multispectral Visible Imaging Camera (MVIC)
panchromatic, blue, and red filter observations were used to approximate
bolometric albedo. The LORRI and MVIC data were from the NASA Planetary Data
System (PDS) Small Bodies Node (SBN) v3.0 archive. Regions south of 38 degrees
South were in winter darkness (polar night) during the New Horizons flyby of
Pluto and the map does not include areas south of approximately 30 degrees
South.

The map was produced using the USGS Integrated Software for Imagers and
Spectrometers (ISIS). The mapping group parameters are:

  ProjectionName     = Equirectangular
  CenterLongitude    = 180.0
  CenterLatitude     = 0.0
  TargetName         = pluto
  EquatorialRadius   = 1188300 <meters>
  PolarRadius        = 1188300 <meters>
  LatitudeType       = Planetocentric
  LongitudeDirection = PositiveEast
  LongitudeDomain    = 360
  MinimumLatitude    = -49.381884697957
  MaximumLatitude    = 90.0
  MinimumLongitude   = 0.0
  MaximumLongitude   = 360.0
  PixelResolution    = 879.23076275961 <meters/pixel>

Pluto's incidence-angle-average bolometric hemispherical albedo,
spatially-averaged over areas north of approximately 30 degrees South, is
approximately 0.54. Pluto has three general albedo categories: 1) very low
albedo southern equatorial terrains including Cthulhu, 2) high albedo terrains
that constitute most of Pluto’s surface, and 3) very high albedo terrains
including Sputnik Planitia. Pluto’s extraordinary albedo variability with
location is also spatially sharp at some places.

Users are strongly encouraged to read the publication titled 'Bolometric
Hemispherical Albedo Map of Pluto from New Horizons Observations' in the
Planetary Science Journal by Hofgartner et al. in 2023 for further information,
including data used, methods, uncertainty, and interpretation.

We thank the entire NASA New Horizons team for enabling the production of this
map. Financial support from the NASA New Frontiers Data Analysis Program (NFDAP)
is gratefully acknowledged (Grant Number 80NSSC22K1118). Constructive reviews of
the map and documentation by Jian-Yang Li, Xiao-Duan Zou, and the SBN team
improved this archive.