One of the unique features of the MODIS instrument is its
Direct Broadcast capability – in addition to storing
data for later download at designated intervals, MODIS immediately
broadcasts the raw data it collects on the chance that someone
on the ground below is listening. The Terra MODIS instrument
was one of the first satellites to constantly broadcast data
for anyone with the right equipment and software to download,
free of charge.
The MODIS direct broadcast system began with Terra on Monday,
April 24, 2000, and for Aqua on July 12, 2002. Both broadcast
full-time except when passing over any of NASA’s Deep
Space Network antennas that are actively tracking a remote
spacecraft. It is estimated that this will occur less than
two hours per day. (For more information, please visit the
Direct Readout Website.)
Generally, spacecraft collect data and store it on board until
it passes over a ground station set up to receive the data,
at which point it transmits the data in one large batch. This
avoids losing data taken when the spacecraft is out of sight
of any ground stations, such as when it is over the ocean.
But the advantage to continually broadcasting the data is
that many sites have the antennas and other necessary equipment
to receive and process MODIS Direct Broadcast data.
The data stream carries the data from all 36 spectral bands
for the entire MODIS field of view. The data can be transmitted
directly from the spacecraft to ground stations equipped with
an average 3m or larger X-band receiving system and appropriate
hardware and software. The Overpass Predictor can be used
to determine when there will be a Terra or Aqua spacecraft
overpass at any location that may have a MODIS Direct Broadcast
The following sites have direct broadcast imagery and/or more
information regarding direct broadcast:
The University of Wisconsin – Madison’s
Space Science and Engineering Center (SSEC)
Provides access to images and information on Terra and Aqua
MODIS direct broadcast data for the current day. It also provides
links to the actual data, orbital tracks, and the hardware
and software necessary to receive direct broadcast data.
The University of Miami’s Rosenstiel School
of Marine and Atmospheric Science (RSMAS)
Provides access to four types of direct broadcast data images
– true color, daytime SST, nighttime SST, and Chlorophyll
a_2. The images are available by individual days, and the
data themselves are available for download via an ftp site.
The Goddard Space Flight Center’s Direct Readout
Provides access to Terra and Aqua MODIS direct broadcast data,
Quick-Look images, viewing software, ephemeris data, and information
about the hardware and software necessary to receive direct
broadcast data. This site also provides Direct Broadcast data
for other instruments on the Aqua and Terra spacecraft.
Oregon State University’s MODIS Direct Broadcast
Provides access to ocean data and images, a data browse tool
(for ordering), an overpass times tool, and recent weather
Earth Observatory Direct Broadcast
Has images acquired from the NASA/GSFC receiving station,
as well as general informatio regarding MODIS Direct Broadcast.
Also contains a link the the Earth Observatory Overpass Predictor,
a handy tool for finding out when a specific satellite is
going to be over a specific location.
The University of South Florida's MODIS Direct Broadcast
Provides access to a variety of direct broadcast data images
including true color, SST, Chlorophyll a_2, Cholorophyll a_3,
and has links to various coverage areas.
USGS EROS Data Center - MODIS Direct Broadcast
The EDC has been processing and distributing MODIS DB data
since July of 2002, and currently has the processing capability
to produce seven levels of products. Their site has a wide-ranging
collection of information regarding the Direct Broadcast project.
USDA Forest Service Remote Sensing Applications Center (RSAC)
The USDA Forest Servcice utilizes MODIS DB data to support interagency, strategic fire management. Access to MODIS imagery, fire detection data and other geospatial productsare provided for near real-time active fire detection and monitoring covering the United States and Canada.
University of Tokyo's Institute of Industrial Science MODIS
Data Service Center
Provides direct broadcast imagery, as well as variety of archived data images, of South and East Asia. There are a number of data products spanning the science team disciplines also available of this region.