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Nimbus Series

          The Nimbus I satellite was launched from Vandenberg Air
Force Base on August 28, 1964, using a Thor-Agena B launch vehicle.
The project objectives were to provide improved photographs of local
cloud conditions by an automatic picture transmission (APT) system,
and to evaluate an advanced vidicon camera system for daylight
coverage and a high-resolution infrared radiometer system for
night-time cloud cover observation.

          Premature Agena cut off resulted in an elliptical orbit of
263 to 579 miles at an 80 degree inclination, rather than the intended
circular orbit.  The satellite's solar panel drive failed on September
23, after Nimbus had returned more than 27,000 excellent photos.  The
vidicon camera systems spotted five hurricanes and two typhoons in
photographing 70 percent of the world each day.  The APT system
supplied daytime photos to more than 60 low-cost ground stations.
Radiometer photos were remarkably clear and covered a 12,500 square
mile area.  A photo of the Antarctic taken at midnight showed four
black dots determined as mountains at the edge of the continent.
Further analysis indicated a strong possibility of volcanic activity
in the mountains.  Nimbus I's stabilization system worked well during
its operational lifetime.

NIMBUS II


          Nimbus II was launched from Vandenberg Air Force Base on May
15, 1966, by a TAT-Agena B launch vehicle.  It was placed in a "high
noon" retrograde orbit of 684 to 734 miles at a 100 degree
inclination.  Sun-synchronous orbit provides ideal lighting conditions
for picture taking.

          The project objectives were to provide global weather
photography on a 24-hour basis for meteorological research and
operational use, and provide infrared data for study of earth's heat
balance.

          Four sensor systems weighing a total of 142 pounds were
carried.  The advanced vidicon camera system (AVCS) included three
1-inch cameras with 800-line resolution designed to photograph a
800,000 square mile area. A high resolution infrared radiometer
provided time and was expected to yield a variety of geophysical and
atmospheric data including cloud height information.


NIMBUS B

          Nimbus B was launched on May 18, 1968, from Vandenberg Air
Force Base by an Air Force Thorad-Agena D launch vehicle.  Two minutes
after launch, a booster malfunction forced a command destruct by the
safety range officer.  The booster and spacecraft fell into the
Pacific Ocean between Vandenberg Air Force Base and San Miguel Island
off the coast of California.  According to radar tracking, the closest
point to shore where debris fell was 5 miles from Jalama Beach and 1
mile from San Miguel Island.  The radioactive fuel for the two
generators (plutonium 238) was contained in two high-strength alloy
and graphite capsules, which had been designed and tested to withstand
ocean impact and seawater corrosion in case of such an abort.
Extensive tests have shown that under these conditions the fuel would
present no hazard to people or marine life.


NIMBUS III

          Nimbus III was launched from Vandenberg Air Force Base on
April 14, 1969, by a Thorad-Agena D launch vehicle.

          Nimbus III was composed of three major elements:  a
5-foot-diameter sensory section, a hexagonal upper section, and two
8-by-3-foot rotating solar panels.  The upper and lower sections were
connected by a truss structure.  A sensory ring, a hollow circular
section, contained all the weather-measuring experiments as well as
spacecraft batteries, transmitters and associated electronic
equipment.  The stabilization and attitude control subsystem, housed
in the upper section, was Earth oriented and stabilized within one
degree on three axes.  The satellite was 10 feet high and 11 feet
across the solar panels.  The weight of 1269 pounds was a heavyweight
record for meteorological satellites.

          Nimbus III was a replacement for Nimbus B which was
destroyed in a launch failure in May 1968.  Nimbus III was to be the
first United States satellite to make night and day global
measurements from space of temperatures of the atmosphere, both over
extended periods and, for the first time, at varying levels
vertically.  Obtaining such meteorological data, principally from over
large bodies of water and marginally habitable land masses, and on
such a scale, was to make possible experimental computerderived
weather predictions, using mathematical models based on the scope of
the numerical data Nimbus III would return.  While meteorological
objectives were primary, this mission also was to gather vital
oceanographic data for scientific purposes other than solely for
weather forecasting.  Another mission objective was to provide data
for the first experiment of the U.S.A. portion of the Global
Atmospheric Research Program (GARP), which was an international
program of formulating and coordinating research for achieving
long-range global weather forecasting.

          Nimbus III was launched after two delays.  One delay was
caused by a propellant leak in the Agena, and the other was due to a
launch priority at the range.  The transmission of data from the
seven meteorological experiments was as scheduled.  All systems and
payload functioned normally.


NIMBUS IV


          The Nimbus IV satellite was launched from Vandenberg Air
Force Base on April 8, 1970, by a Thorad-Agena D launch vehicle.  It
was placed in the planned, circular, near-polar orbit.  It made
world-wide weather observations twice a day - once in daylight and
once in darkness.

          Nimbus IV was a continuation of the spacecraft series to
serve as a testbed for research and development of new meteorological
sensors, subsystems and systems configurations.  Some of the
technology developed in the Nimbus program was transferred to TIROS
operational weather satellites.  The meteorological objectives were to
study spatial and temporal distribution of the atmospheric structure,
particularly temperature, ozone, and water vapor, and to determine
temporal variation in the solar radiation in the near ultraviolet.

          Nimbus IV was butterfly-shaped with a 5-foot diameter
sensory ring lower section which housed experiments and supporting
equipment.  A hexagonal upper section contained the attitude control
system.  Two solar panels, 8 feet by 3 feet, provided more than 200
watts of power supplemented by two generators.  The overall height was
10 feet; width was 11 feet.  The orbital weight was 1366 pounds.


NIMBUS E

          Nimbus E was launched from the Western Test Range,
Vandenberg Air Force Base, on December 11, 1972, by a Delta 900 launch
vehicle.

          It was a butterfly-shaped spacecraft with a 5-foot diameter
ring lower section housing experiments and supporting equipment.  A
hexagonal upper section contained the attitude control system.  Two
solar panels provided more than 200 watts of power.  The overall
height was 10 feet; width was 11 feet.  The three-axis stabilized
spacecraft weighed 1580 pounds.

          Nimbus E was a continuation of development of new
meteorological sensors, subsystems and systems configurations.  It was
an Earth-oriented platform for testing advanced systems collecting
meteorological and geological data.

NIMBUS F

          Nimbus F was launched from the Western Test Range,
Vandenberg Air Force Base, on June 12, 1975, by a two-stage Delta 2910
launch vehicle.  It was placed into a near-polar, circular orbit.

          A meteorological satellite, similar in design to other
Nimbus satellites, Nimbus F weighed 1823 pounds. It was designed to
test instruments for remote sensing of the Earth's atmosphere.

NIMBUS G

          The Nimbus G satellite was launched from Vandenberg Air
Force Base on October 24, 1978, by a Delta 2910 launch vehicle.  It
was placed in a circular, near-polar orbit with an inclination of 99.3
degrees and a period of 104 minutes.

          Similar to the other satellites in this series, Nimbus G was
butterfly-shaped.  Spacecraft and experiment data were transmitted to
Earth stations immediately, or stored in an on-board high-speed tape
recorder for subsequent playback when the satellite was in view of a
ground acquisition station.

          Nimbus G was the first satellite to provide continuous,
worldwide environmental data to help scientists throughout the world
determine the physical characteristics of the global atmosphere, the
oceans, the dynamic atmosphere-ocean interface, and the Earth's heat
balance.  For the first time, the European Space Agency (ESA) received
and processed direct Nimbus G data at Lannion, France.

Comments and questions: Jennifer Green
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