College of Science Seminars
ESGS Seminar
The Geostationary Lightning Mapper for GOES-R and Beyond
Abstract
The Geostationary Lightning Mapper (GLM) is a single channel, near-IR imager/optical transient event detector, used to detect, locate and measure total lightning activity over the full-disk as part of a 3-axis stabilized, geostationary weather satellite system. The next generation NOAA Geostationary Operational Environmental Satellite (GOES-R) series with a planned launch in 2014 will carry a GLM that will provide continuous day and night observations of lightning from the west coast of Africa (GOES-E) to New Zealand (GOES-W) when the constellation is fully operational. The mission objectives for the GLM are to 1) provide continuous, full-disk lightning measurements for storm warning and nowcasting, 2) provide early warning of tornadic activity, and 3) accumulate a long-term database to track decadal changes of lightning. The GLM owes its heritage to the NASA Lightning Imaging Sensor (1997-Present) and the Optical Transient Detector (1995-2000), which were developed for the Earth Observing System and have produced a combined 13 year data record of global lightning activity. In parallel with the instrument development, a GOES-R Risk Reduction Team and Algorithm Working Group Lightning Applications Team have begun to develop the Level 2 algorithms and applications. Proxy total lightning data from the NASA Lightning Imaging Sensor on the Tropical Rainfall Measuring Mission (TRMM) satellite and regional test beds (e.g., Lightning Mapping Arrays in North Alabama and the Washington DC Metropolitan area, the latter in partnership with GMU) are being used to develop the pre-launch algorithms and applications, and also improve our knowledge of thunderstorm initiation and evolution. Real time lightning mapping data are being provided in an experimental mode to selected
National Weather Service (NWS) forecast offices in Southern and Eastern Region. This effort is designed to help improve our understanding of the application of these data in operational settings.
Space Sciences Seminar
The Dark Ages Lunar Interferometer (DALI)
Abstract
The Dark Ages represent the last frontier in cosmology, the era
between the genesis of the cosmic microwave background (CMB) at
recombination and the formation of the first stars. During the Dark
Ages, when the Universe was unlit by any star, the only detectable
signal is likely to be that from neutral hydrogen (HI), which will
appear in absorption against the CMB. The HI absorption represents
potentially the richest of all data sets in cosmology—not only is the
underlying physics relatively simple so that the Hi absorption can be
used to constrain fundamental cosmological parameters in a manner
similar to that of CMB observations, but the spectral nature of the
signal allows the evolution of the Universe as a function of redshift
(z) to be followed. The Hi absorption occurs in dark matter-dominated
overdensities, locations that will later become the birthplaces of the
first stars, so tracing this evolution will provide crucial insights
into the properties of dark matter and potentially reveal aspects of
cosmic inflation. Moreover, given the relatively simple physics—the
Universal expansion, Compton scattering between CMB photons and
residual electrons, and gravity—any deviation from the expected
evolution would be a “clean” signature of fundamentally new physics.
The Dark Ages Lunar Interferometer (DALI) is a mission proposed for
study to NASA for a telescope located on the far side of the Moon, the
only site in the solar system shielded from human-generated
interference and, at night, from solar radio emissions. The DALI array
will observe at 3–30 m wavelengths (10–100 MHz; redshifts 15 \le z \le
150), and the DALI baseline concept builds on ground-based telescopes
operating at similar wavelengths, e.g., the Long Wavelength Array
(LWA) and Murchison Widefield Array (MWA). Specifically, the
fundamental collecting element will be dipoles. The dipoles will be
grouped into “stations,” deployed via rovers over an area of
approximately 50 km in diameter to obtain the requisite angular
resolution. The desired three-dimensional imaging requires
approximately 1000 stations, each containing 100 dipoles (i.e., ~ 105
dipoles); alternate processing approaches may produce useful results
with significantly fewer dipoles (factor ~ 3–10). Each station would
be deployed by one rover, which would also serve as a “transmission
hub” for sending the signals for correlation to a central processing
facility. After sending the correlator output to Earth, analysis would
then proceed via standard methods being developed for ground-based
arrays.


