The Lightning Imaging Sensor (LIS) Science Team Meeting was held at the Global Hydrology and Climate Center (GHCC) in Huntsville, AL, on 5-7 June 1995. The primary objectives of the meeting were to discuss algorithm development, calibration/validation plans, geolocation issues, the needs of the science community, and the initial results from the Optical Transient Detector (OTD) experiment. The 35 attendees were offered a tour of the LIS/OTD Science Computing Facility (SCF), a demonstration of interuse tools for browsing OTD data, and a trip to the LIS calibration facility at the Marshall Space Flight Center.
Hugh Christian, LIS Principal Investigator, opened the meeting with a brief status report on the LIS instrument development. LIS is a PI instrument being developed for the NASA Earth Observing System (EOS) as a flight of opportunity aboard the Tropical Rainfall Measuring Mission (TRMM). LIS is scheduled for delivery to the Goddard Space Flight Center (GSFC) in December for integration on the TRMM spacecraft. The TRMM is a joint U.S.-Japan mission scheduled for launch in August 1997. For more information refer to:
OTD First Results
Christian presented the first results from the OTD experiment. OTD is a scientific payload on the Orbital Sciences Corp. (OSC) MicroLab 1 "small sat" satellite. The MicroLab 1 was launched by a Pegasus rocket in April 1995. The primary mission of the OTD is to improve our understanding of thunderstorm distributions, cloud processes, and storm variability by detecting and locating lightning activity over large areas of the Earth's surface. The nominal orbit is 740 km altitude with a 70 degree inclination, providing an instantaneous Earth view in excess of 1300 km x 1300 km. In comparison, the LIS on TRMM will have a nominal orbit of 350 km altitude with a 35 degree inclination and an instantaneous field of view of 600 km x 600 km. The OTD (and LIS) will detect lightning during both daytime and nighttime with spatial resolution of approximately 10 km (4 km) and temporal resolution of 2 milliseconds.
The OTD and satellite data are downlinked approximately twice a day to the OSC tracking station in Fairmont, WV. The data are transmitted from Fairmont via a T1 line to the OSC Science Operations and Control Center (SOCC) located at Dulles, VA. From Dulles, the OTD data are shipped overnight on 8 mm tape to the LIS/OTD SCF at the GHCC. Mission status reports are retrieved from the SOCC using ftp file transfers.
Raw OTD data are archived at the Earth Observing System Data and Information System (EOSDIS) Distributed Active Archive Center (DAAC) for Hydrology located at the GHCC . Science data processing and quality assurance are performed within the LIS/OTD SCF. OTD science products will be distributed from the DAAC.
Early results of the OTD experiment were presented at the International Union of Geodesy and Geophysics (IUGG) meeting held in Boulder, CO in July. Oral and poster papers will be presented in Session A10 at the fall American Geophysical Union (AGU) meeting in San Francisco.
OTD plans for FY 1996 are:
OTD Geolocation
The SDP Toolkit was not available to the LIS Science Team in early April when the OTD was launched. Therefore, the LIS Science Team worked in collaboration with the JPL NAIF Team and the EOSDIS Interuse Team at the University of Alabama in Huntsville to use the JPL-developed SPICE tools for OTD geolocation and orbit modeling. Bill Table of JPL presented an overview of the SPICE toolkit and its use in OTD geolocation. Custom software was developed for OTD kernel creation and geometry analysis. The OTD was brought into the SPICE environment quite readily. Having dynamic attitude and ephemeris data prior to launch was an important factor in producing early (within 48 hours) results from the OTD experiment. The Interuse Team presented visualization tools for browsing OTD data and calibration/validation data sets. Sample images are on the LIS/OTD home page.
SSM/I Studies
The LIS/OTD Science Team is collecting coincident observations from the OTD, the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I), geostationary satellite imagery, ground-based lightning networks, and WSR88-D NEXRAD sites to create proxy data sets for the TRMM sensor suite. Ed Zipser (Texas A&M University) presented results from on-going studies using radiances and products, e.g., 85 GHz polarization-corrected temperature (or PCT) to create climatologies of mesoscale weather systems and compare ice scattering signatures with lightning and radar observations. On a global scale we jointly plan on comparing mesoscale weather system structures observed by the SSM/I with the OTD data. Jim Weinman (GSFC) discussed on-going SSM/I and mesoscale model comparisons with the U.K. Meteorological Office long-range, low-frequency (9.8 kHz) lightning network. The LIS/OTD Science Team is using the U.K. system in calibration/validation and performance assessment studies.
Ground Truth and Field Campaigns
The plans of the TRMM ground-truth team were discussed. The LIS/OTD Science Team plans on obtaining additional ground-based lightning observations in the vicinity of the TRMM ground-truth sites having weather radars and a rain gauge networks. Existing lightning sensing systems are providing data from Cape Canaveral, Florida. The LIS/OTD Science Team will be deploying a lightning network to Darwin, NT Australia in time for the Maritime continent Thunderstorm Experiment (McTEX) being conducted at the Tiwi Islands from November to December 1995 to better understand tropical cloud properties, microphysics, and kinematics. At the conclusion of McTEX, the lightning network will continue in operation on the mainland for the duration of the TRMM project (FY 2000). The system being deployed for McTEX is similar to the system provided by the LIS/OTD Science Team for the TOGA-COARE experiment. An additional lightning network is being considered for the TRMM site at Kwajalein Atoll. Collaborations with NOAA and industry and university scientists will provide additional calibration/validation data bases in the U.S. and overseas.
Lightning and NOx Production
Each LIS/OTD science meeting attempts to include a special topic or theme for general discussion amongst the participants. At this meeting, we chose "the role of lightning in NOx production." Recent fall AGU meetings have had papers debating the role of lightning in the global budget of NOx. Various atmospheric chemists have made inquiries on the existence of global lightning data bases (to support modeling and monitoring studies) and tropical oceanic data bases (to support field campaigns such as Transport and Atmospheric Chemistry near The Equator-Atlantic [TRACE-A] or Pacific Exploratory Mission [PEM]). The LIS/OTD global lightning data bases are expected to greatly improve the lightning data base for such investigations. Colin Price (formerly of the Lawrence Livermore National Laboratory) and Chip Levy II (NOAA/Geophysical Fluid Dynamics Laboratory) discussed their model parameteriations of the NOx production rate by lightning. Laboratory and in situ data suggest a range of 1-100 Tg N per year. The GFDL model uses a production rate of 3 Tg N per year with assumptions that all storms have a single lightning distribution, that all cloud flashes and ground discharges have the same flash energy, and that NOx production is proportional to flash energy. OTD and ground-based measurements will also help us to better understand the ratio of cloud flashes to ground flashes and factors controlling that ratio.
Multiple Satellite and Coincident Data Collection
One of the objectives of the OTD mission is to collect coincident data sets with other lightning and storm observing systems. For example, prior global lightning distributions at local midnight have been produced from the DMSP satellite Optical Linescan System (OLS). The OLS senses lightning only at night, and with low detection efficiency. OTD coincident observations are being used to help understand the sampling biases in this type of data base. A few coincident case studies have been acquired with the OTD so far.
The ALEXIS/Blackbeard satellite operated by Los Alamos National Laboratory (LANL) senses RF emissions that appear to be associated with thunderstorms. The satellite is in an 800 km, 60 degree inclination orbit. Tim Murphy of LANL presented Blackbeard observations of the recently discovered Trans Ionospheric Pulse Pair (TIPP) events. The TIPP emission is very different from typical lightning emissions. Collaboration with the LIS/OTD team will attempt to provide coincident OTD measurements to help confirm the coexistence or absence of optical emissions from lightning discharges in the vicinity. Murphy also discussed the status of the planned 1996 launch of the follow-on FORTE satellite. The FORTE spacecraft is unique in that it is an all-carbon-composite structure. FORTE sensors will collect simultaneous RF and optical signals. These data will be made available to the LIS/OTD Science Team.
The LIS/OTD Science Team is also collaborating with the Gamma Ray Observatory (GRO) Burst and Transient Source Experiment (BATSE) Science Team. A number of terrestrial gamma ray flashes have been observed by BATSE in association with thunderstorms. We are on the "look-out" for lightning associated with the storms producing these bursts, using a combination of OTD and ground-based lightning detection systems. An orbit modeling program, initially developed by the DAAC, has been enhanced in the LIS/OTD SCF to predict coincident observation periods for OTD with these various satellites.
There is great interest in the atmospheric chemistry and space physics communities in upward lightning discharges and so-called red sprite and blue jet phenomena in the upper stratosphere and middle atmosphere. OTD coincidence data collection with ground-based and airplane measurements of these phenomena is on-going and planned for the future. An additional opportunity may arise next year for coincident satellite observations of these events. David Pollock of the University of Alabama in Huntsville presented an overview and status of the Midcourse Space Experiment (MSX) mission. The MSX suite of UV and infrared sensors may provide information on various chemical species in the atmosphere as well as information on the temporal and spectral characteristics of sprites. Coincident OTD observations of lightning with these measurements are of interest and will help to further develop the competing theories proposed to explain these phenomena.