Weather Surveillance by Satellite
March 1967 Electronics World
take for granted most of the technology that surrounds us. Unless you
were alive 50 years ago at the dawn of microelectronics and space flight,
it would be difficult to imagine a world without cellphones, desktop
computers, color TVs, the Internet, and even satellite-base weather
forecasting. Everyone likes to make jokes about weathermen being no
better at predicting the weather than your grandmother's roomatiz[sic],
but the fact is that, especially for short-term (2-3 days) predictions,
we get pretty good information. As a model airplane flyer, I check the
wind level forecast nearly every day to see whether my plane can handle
it. AccuWeather's free hourly forecast is usually pretty darn accurate
for today's and tomorrow's wind - to within a couple MPH. A plethora
of ground reporting stations help improve accuracy, but data streamed
from spaceborne instruments are the real key. This story in the 1967
Electronics World reports on some of the earlier imaging weather satellites.
Amusingly, it also predicts the possibility of someday controlling world
weather with the satellites' assistance.
March 1967 Electronics World
of Contents] People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Electronics World
was published from May 1959 through December 1971. All copyrights are hereby acknowledged.
Electronics World articles.
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Electronics World articles.
Weather Surveillance by SatelliteBy Joseph H. Wujek, Jr.
Tiros, Nimbus, and successor ESSA satellites
are providing global weather information that may one day lead to global
To a great extent, man has learned to use the forces of nature beneficially.
A notable exception is our inability to control those forces in nature
which we know collectively as weather. Weather plays an important part
in social and economic well-being of a nation. Agricultural output is
strongly tied to the weather, as is the movement of ships at sea, aircraft,
and land transport. Indeed, commerce as a whole depends to some degree
on the behavior of the elements. In war as in peace, a nation's fate
may be decided by the perversities of the weather. The defeat of the
Spanish Armada, as well as the defeat of Napoleon's armies on the plains
of Russia, were due in large measure to severe weather conditions.
The new "cartwheel" Tiros photographs the earth as the satellite
rolls along like a wheel in a near-polar orbit.
In view of all this, it is not surprising that meteorologists
continually searching for new tools to aid them in understanding the
weather. With increased knowledge of weather comes the ability to predict
the kind of weather a region will experience. President Johnson, when
Vice-President and Chairman of the National Aeronautics and Space Council,
estimated the saving which our nation could realize if accurate weather
predictions were available only five days in advance. These yearly savings
include: $2.5 billion in agriculture; $45 million in the lumber industry;
$100 million in surface transportation; $75 million in retail marketing;
and $4 billion in water resources management. Beyond these dollar savings,
we have the priceless savings in human life which result when hurricanes,
tidal waves, and the like are detected in advance. Clearly, then, research
into the nature of weather will have a profound effect upon our welfare.
Until early 1960, meteorologists were somewhat earth-bound in
their measurements of weather phenomena. True, aircraft and weather
balloons were launched to measure wind speed, barometric pressure, and
other weather variables. Later, sounding rockets were also used to obtain
these measurements. But these measurements are somewhat localized in
that only a small region of the atmosphere or stratosphere is sampled.
And, as we know, weather is by no means predictable by immediate local
conditions. A storm front in the far reaches of Canada's Hudson Bay
on Tuesday can create havoc with cattle ranches in North Dakota on Thursday.
Even with many remote weather stations positioned at strategic points
around the world, severe weather conditions can be building up while
unobserved by these stations. A system for weather surveillance which
could survey large sectors of the earth was urgently needed.
The Tiros Satellite System
This view of the Nile River and its Delta, the Red Sea, and the
eastern Mediterranean was taken by Tiros III from an altitude of
The vortex of the Hurricane Daisy photographed several year ago
off the east coast of the United States by the Tiros V satellite.
The Tiros VII being checked out prior to its launch into space.
The APT ground receiving system uses fairly simple, inexpensive
ground-based equipment which employs conventional facsimile recorder.
The Tiros (Television
Infra-Red Observation Satellite) series provides a partial solution
to this requirement. These vehicles, equipped with television cameras
and infrared (IR) radiometers, gather data for analysis by meteorologists
within hours after the observation. The first in the series, Tiros I,
was launched from Cape Kennedy on April 1, 1960. At this writing, ten
Tiros satellites have been launched.
Table 1. Specs for Thor-Delta booster which launched Tiros.
The Tiros is an 18-sided vehicle, 22 inches high by 42 inches
in diameter, weighing about 300 pounds. Each of the 18 faces of the
satellite is an array of solar cells. These 900 solar cells furnish
charging current for the 63 nickel-cadmium cells which furnish power
throughout orbit. Two 18·inch receiving antennas extend from the top
of the satellite and are used to receive ground commands. Four 22-inch
telemetry transmitting antennas are located on the underside of the
package. Tiros I through VIII had two vidicon TV cameras mounted on
the underside of the satellite. Later Tiros spacecraft have side-looking
TV cameras mounted on opposite sides.
The Tiros series is put
into orbit by the three-stage ThorDelta launch vehicle. Table 1 gives
important specifications for this space booster. For some perspective,
recognize that jet engines used on modern commercial airliners have
typical ratings of 16,000 pounds thrust per engine. Hence, the first
stage alone of the launch vehicle delivers more thrust than ten of these
aircraft engines. Launch vehicles have since been developed which generate
more than two million. pounds of thrust.
Tiros orbits range
from 450 miles to 860 miles, with periods (time for one revolution)
of 90 minutes to 113 minutes, respectively. At the 450-mile orbit a
region on earth of 800 to 1000 miles in diameter is covered by one transmitted
Tiros I through VIII were placed in a general east-west
orbit, resulting in coverage of about 25% of the earth's surface. Later
Tiros launches resulted in a north-south, or polar orbit. The polar
orbit permits coverage of nearly all the earth's surface. The polar
orbit is also selected so as to be nearly synchronous with the sun.
The sun-sync orbit results in backlighting from the sun during the northward
pass of the satellite, producing high-quality photographs.
I-VII made use of a focal-plane shutter in conjunction with the two
vidicon TV cameras. Pictures are stored
on the tube face and converted
to data bits for storage on magnetic tape or direct readout by ground
stations. Each orbit results in 64 pictures, or 32 pictures per tape.
Transmission of data to the ground station requires about three minutes.
The data transmission simultaneously erases the magnetic tapes for the
next data-gathering pass. The operation of the readout system as well
as the timing of the picture-taking sequence is accomplished by ground
command. The ground command sets timers which activate the camera system
when the satellite passes over the region of interest.
with Tiros VIII, a new system of data readout was used. The new system
is designated Automatic Picture Transmission (APT). Rather than construct
a TV picture line by line, electronically photograph the screen, and
then store or transmit, APT uses a system similar to that used by newspapers
and the press services to transmit photos. A facsimile recorder then
reproduces the picture as received.
Ground receiving stations
for Tiros are Wallops Island, Virginia; San Nicolas, California; and
Fairbanks, Alaska. Over-all direction of the Tiros system stems from
Goddard Space Flight Center, Greenbelt, Maryland. These stations are
capable of receiving data when the satellite draws to within 1500 miles
of the station. The received pictures are photographed by 35-mm camera
for immediate analysis by meteorologists. In particular, these photos
reveal conditions of cloud cover as well as the presence of hurricane
In addition to the TV camera, infrared radiometers
measure the amount of reflected and absorbed solar IR energy. The amount
of IR energy absorbed and reflected determines the heat balance of the
earth and therefore affects the weather. The IR data is transmitted
and received as non-photographic data. This data is later reduced and
plotted on weather maps for analysis. While the IR data is not immediately
useful to meteorologists, it nevertheless provides a kind of long-range
weather behavior of our planet.
The initial design of Tiros called
for a mission life of three to four months. The first Tiros was operational
for 2 1/2 months. Later Tiros vehicles operated for well over one year.
In the first three years of operation some 300,000 TV photographs were
transmitted. Tiros I completed 1302 orbits and relayed 22,592 pictures
to ground stations.
As seen in the accompanying photographs,
Tiros has produced some startling results. Of particular importance
were other photos taken by Tiros III in Sept. 1961. These photos revealed
the build-up of Hurricane Carla. As a result of this early warning,
approximately 350,000 persons withdrew from the storm region involved
and injuries and loss of life were held to an absolute minimum.
to the ten Tiros launchings, two each ESSA (Environmental Survey Satellite)
and the Nimbus satellites that have been orbited.
The ESSA satellites
are similar to the earlier Tiros systems and operate in the "cartwheel"
mode. ESSA I was launched on February 3, 1966 and carried two half-inch
vidicon TV cameras into a circular 460-mile-high polar orbit,
having a period of about 100 minutes. ESSA II carried two APT cameras
into a circular 860-mile-high polar orbit with a 113-minute period.
NASA plans to keep two ESSA satellites in orbit at all times. As one
ESSA vehicle ceases to transmit, a replacement will be launched. The
ESSA satellites represent the operational system for which the Tiros
vehicles were the research and development packages.
Nimbus represents a more sophisticated weather satellite system. In
particular, Nimbus is not restricted to photographing the earth during
daylight. By means of its high-resolution red radiometer (HRIR) system,
night photos are obtained. These photos appears as dark or light regions,
depending on whether more or less heat is radiated, respectively.
In addition to the HRIR system, three vidicon cameras
are used. From an orbit of 575 miles, resolution of one-half mile is
possible. The APT system was also flown on the Nimbus.
I was moderately successful after launch on August 28, 1964. The second
stage of the launch vehicle did not burn as long as required, resulting
in an elliptical orbit of 252 miles perigee and 578 miles apogee, rather
than the planned circular 575-mile orbit. The satellite transmitted
many useful photos until a solar panel locked and was thus unable to
track the sun. As a result, Nimbus I ceased on September 23, 1964.
Nimbus II was successfully launched May 15, 1966, carrying HRIR,
APT, and vidicon systems. NASA plans to launch a Nimbus satellite approximately
every 18 months. These vehicles will serve to test new systems for improved
weather observations .
The Tiros vehicles and successors form
the Tiros Operational System (TOS), which is a joint undertaking of
the U.S. Weather Bureau and NASA. In addition to the benefits already
listed, the Tiros system may provide scientists with new insight into
such phenomena as clear-air turbulence (CAT) and the nature of the
Perhaps history will someday show that Tiros
provided a significant advance toward a goal we have desired, control
of the weather. A system of sophisticated Tiros-like satellites, relaying
weather data to a central computer which directs corrective (and as
yet unknown) action to smooth the weather, is presently but a dream.
But the translation from dream to design to hardware has been foreshortened
considerably as our technology advances.