Nearsimultaneous Observations of Polar Mesospheric Clouds from the International Space Station and f

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Near-simultaneous Observations of Polar
Mesospheric Clouds from the International Space
Station and from Orbiting Optical Instruments
Donald Pettit1, David W. Rusch2, Gary E. Thomas2,
Aimee Merkel3, Scott Bailey4, J. M. Russell III5,
and Matthew DeLand6



ABSTRACT The orbit of the International Space
Station (ISS) carried the spacecraft to latitudes
high enough for observations of Polar Mesospheric
Clouds (PMC). During the PMC southern-hemisphere
season 2002-2003, a series of digital images and
visual observations were taken over the Antarctic
continent of PMC at the sunlit limb.
Approximately twenty such observations, available
through the ISS LAB window towards the summer
pole, revealed the PMC as a distinct narrow
scattering layer in the upper mesosphere, often
many thousands of kilometers in horizontal
expanse. The field of view from the ISS covered
a sufficiently wide area of the polar region,
that it was possible to co-locate measurements
taken by instruments on board unmanned spacecraft
in the near vicinity of the Space Station (but
taken from a higher altitude). This provided an
opportunity to combine accurate limb scans and
nadir views of PMC with high-resolution
information on the horizontal spatial structure.
The SNOE and NOAA-16 and NOAA-17 SBUV/2
instruments obtained 15 orbits per day of PMC
measurements at UV wavelengths. In addition, the
SABER experiment on board the TIMED satellite
obtained temperature profiles in the same
vicinity. We will report on the first comparisons
of these data, and describe the specific
advantages of this unique combination of data.
1. NASA JSC, Houston, TX 77058 2. LASP,
University of Colorado, Boulder, CO
80309-0392 3. National Center for Atmospheric
Research, Boulder, CO 80303 4 Geophysical
Institute, University of Alaska at Fairbanks 5.
Center for Atmospheric Sciences, Hampton
University, Hampton, VA 23668 6. SSAI, 10210
Greenbelt Rd., Suite 400, Lanham, MD 20706
The orbit of the International Space Station
(ISS) allows visual and imaging observations of
Polar Mesospheric Clouds (PMC). During the PMC
southern season 2002/3, Science Officer Donald
Pettit made a series of digital images of PMC
displays over the Antarctic continent. We
identify near-simultaneous measurements taken by
instruments on unmanned spacecraft. This provides
an opportunity to compare limb scans of PMC with
information on the horizontal structure. The
clouds identified in SNOE and SBUV measurements
are small cross-sections of much more extensive
cloud layers, which may extend over a thousand
kilometers horizontally. Measurements by SABER
showed that these layers occur in regions where
temperatures lie well below the ice frost point.
The appearance in the limb images is consistent
with the existence of extremely thin mesospheric
clouds at nearly-constant altitude, whose
horizontal dimensions exceed those in the
vertical by three orders of magnitude. These
coincident observations confirm that NLC and PMC
are indeed the same phenomena.
The International Space Station
Astronaut Don Pettit at the viewing window with
his camera.
PMC Photograph by Don Pettit
PMC Photograph by Don Pettit
Enlargement of area in red box
Caption The top picture in each vertical
sequence is the ISS cloud photograph, next is the
ISS position and the direction toward the center
of the image (green arrow). The third image
presents the SNOE observations (squares) color
coded for intensity. The black numbers near the
SNOE data are UTs in hours. The Asterisks are
the locations of the SBUV cloud detections. The
black box is the location of the ISS view of the
PMC. The bottom panel presents coincident
temperature measurements from SABAR, Version 1.04.