Background
The Optical Transient Detector (OTD), the world's first space-based sensor
capable of detecting and locating
lightning events in the daytime as well as during the nighttime
with high detection efficiency was designed
and built at Marshall Space Flight Center (MSFC). The concept for
this instrument was developed at NASA's Marshall Space Flight
Center in the 1980's, and was selected for development as part of NASA's
Earth Observing System (EOS). The purpose of the sensor is to detect the full
spectrum of lightning flashes, including cloud to ground,
cloud to cloud, and intra-cloud (within cloud) lightning events.
Ground-based techniques detect only cloud-to-ground
lightning events which are believed to comprise 25% of the total
lightning activity. In addition, these techniques generally detect
lightning activity near land masses; very little information
is provided regarding lightning events over the Earth's oceans. OTD is designed
to aid scientists in determining the global distribution of
lightning activity and thunderstorms and the characteristics of the Earth's
electric circuit.
The OTD was launched on 3 April 1995 into a
near polar orbit at an inclination of 70 degrees
with respect to the equator, at an altitude of 740 km. At any given instant, this
views a 1300 by 1300 km region of the earth.
The OTD development team adopted a
fast-track, low-cost approach, making maximum use of engineering model hardware
configured for flight on a small satellite. Launch on the Orbital Sciences
Corporation
Pegasus rocket
was provided free via a data buy arrangement providing low cost access to space
with a shared government-industry risk factor. The instrument was designed,
fabricated, space qualified, calibrated, and delivered within a period of nine
months. It is designed to observe lightning for a period of
two years or more.
The
Microlab satellite
carrying the
OTD (silver canister)
shared the launch with two commercial communications satellites called Orbcoms.
Scientific Objectives
OTD is designed to detect, locate and measure the intensity of lightning for scientific
investigation of the distribution and variability of total lightning over
the Earth and to increase our understanding of the Earth's atmosphere system.
Lightning is closely coupled to storm convection dynamics, and can be
correlated to the global rates, amounts and distribution of convective
precipitation. The
Optical Transient Detector
contributes to studies of
Earth's water cycle, sea-surface temperature variations, electrical coupling
of thunderstorms with the ionosphere and magnetosphere, and modeling of the
global distribution of electrical fields and currents in the Earth's
atmosphere. In addition, it begins the development of a global lightning
climatological database for use in NASA's Mission to Planet Earth Global
Climate Change Program.
Educators Section
- A Lightning Fieldtrip
- Take a fieldtrip with students to understand the nature and hazards of
lightning. Geared toward middle school students. Explains the principles
behind what lightning is and how it is generated.
Investigates the effects of lightning on Earth and in the atmosphere.
Program runs 25 minutes. It may be seen on NASA Select TV. Next airing
scheduled for
February 25, 1997.
NASA Educational TV schedule
"A Lightning Fieldtrip" -
Excerpt MPEG format (797,988 bytes)
- OTD Results - Lightning Flash Rates and Tornado Formation
- A six minute NASA Video newsclip interviewing Hugh Christian, Principal
Investigator of OTD. The discussion centers around the relationship
of lightning flash rates and tornado formation and how the OTD sensor
may help further clarify and identify these situations.
Available from MSFC Public affairs office. Contact Steve Roy (205) 544-6535
or e-mail (steve.roy@msfc.nasa.gov).
Mission Status
The Pegasus rocket was successfully launched the morning of April 3, 1995.
The satellite, and payload are operating as expected, and continues to
operate nominally since that time. The satellite and payload have successfully
completed over 20 months of operation.
Example Data
First data from the OTD sensor
Tornadic Thunderstorm Over Oklahoma (April 17, 1995)
Storms near the Red Sea: April 26, 1995
SouthEastern United States (May 19, 1995)
Mission Summaries
May 1, 1995 - April 30, 1996
World Summary from day of launch
United States Summary from day of launch
Monthly Summaries
Flash summary maps represent optical events which are detected within the field
of view of the OTD.
World
- 1995
-
April,
May,
June,
July,
August,
September,
October,
November,
December
1995 Summary
- 1996
-
January,
February,
March,
April,
May,
June,
July,
August,
September,
October,
November,
December
1996 Summary
- 1997
-
January,
February,
March,
April,
May,
June,
July,
August,
September,
October,
November,
December
1997 Summary
United States
- 1995
-
April,
May,
June,
July,
August,
September,
October,
November,
December
1995 Summary
- 1996
-
January,
February,
March,
April,
May,
June,
July,
August,
September,
October,
November,
December
1996 Summary
- 1997
-
January,
February,
March,
April,
May,
June,
July,
August,
September
October
November
December
1997 Summary
Optical Transient Detector (OTD) / Operational Linescan System (OLS) Comparison
- 1995
-
May,
June,
July,
August,
September,
October,
November
National Lightning Detection Network (Cloud-Ground Flashes) Coincident with OTD
- 1995
-
May
National Lightning Detection Network Summaries (RESTRICTED ACCESS)
- 1995
-
April,
May,
June,
July,
August,
September,
October,
November,
Year to Date
2.5° x 2.5° Global Seasonal Summary
- 1995
-
June-July-August
Coincident OTD Events / 1995 Atlantic Hurricanes
Coincident data from the McTEX experiment over North Australia
Movie Sequences (MPEG format)
Sensor Characteristics
OTD technological innovations include a narrowband, very stable, refractory
oxide interference filter; a high-speed (f/1.6)
telecentric telescope assembly;
a high-speed focal plane which processes 500 images per second; and a
real time event processor
which processes 10 million pixels per second to extract
lightning signals from a bright daytime background.
TRMM Mission Simulation Data
LIS Lightning Browse Product
Reports
Lightning Imaging Sensor (LIS) Science Team Meeting (5-7 June 1995)
Lightning Imaging Sensor (LIS) Science Team Meeting (13-14 March 1997)
Bibliography
Christian, H.J., R.J. Blakeslee, and S.J. Goodman, The Detection of Lightning
from Geostationary Orbit,
Journal of Geophysical Research,
Vol. 94, 13,329-13,337, 1989.
Christian, H.J., R.J. Blakeslee, and S.J. Goodman, Lightning Imaging Sensor
(LIS) for the Earth Observing System, NASA Technical Memorandum 4350, MSFC,
Huntsville, AL, February, 1992.
Investigators
-
Dr. Hugh J. Christian (PI)
(hugh.christian@msfc.nasa.gov)
- Dr. Steven J. Goodman (steve.goodman@msfc.nasa.gov)
- Dr. Richard J. Blakeslee (richard.blakeslee@msfc.nasa.gov)
- Dr. Douglas M. Mach (doug.mach@msfc.nasa.gov)
- Dr. Kevin T. Driscoll (driscoll@corona.msfc.nasa.gov)
Notice to Scientific Investigators
The information and imagery found on this web page were created in an effort to
rapidly disseminate OTD data, and are therefore unlikely to be suitable for use
in scientific publications. If you wish to obtain OTD data for specific time periods,
we request that you acquire the data through the
Marshall Space Flight Center DAAC
(available April, 1996) or directly at the
MSFC GHRC
OTD homepage
. For more information on OTD data please contact the
investigators listed above.
If you include any of the images or information directly from this web page in a
presentation or publication, please provide the page curator with the title, date,
and forum of the publication. In addition, we request that you acknowledge
NASA/Marshall Space Flight Center and the Global Hydrology and Climate Center (GHCC).
The development of the OTD instrument was funded through NASA's Earth Observing
System (EOS).
Global Hydrology and Climate Center
Responsible Official: Dr. James E. Arnold
(jim.arnold@msfc.nasa.gov)
Page Curator: Paul J. Meyer
(paul.meyer@msfc.nasa.gov)
Last Updated: August 27, 1997
