The Nimbus
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
s were second-generation U.S.
robotic spacecraft launched between 1964 and 1978 used for
meteorological research and development. The spacecraft were designed to serve as stabilized, Earth-oriented platforms for the testing of advanced systems to sense and collect
atmospheric science data. Seven Nimbus spacecraft have been launched into near-polar,
sun-synchronous orbits beginning with Nimbus 1 on August 28, 1964. On board the Nimbus satellites are various instrumentation for imaging, sounding, and other studies in different spectral regions. The Nimbus satellites were launched aboard
Thor-Agena rockets (Nimbus 1–4) and
Delta rockets (Nimbus 5–7).
Over a 20-year period from the launch of the first satellite, the Nimbus series of missions was the United States' primary research and development platform for satellite remote sensing of the Earth. The seven Nimbus satellites, launched over a fourteen-year period, shared their space-based observations of the planet for thirty years. NASA transferred the technology tested and refined by the Nimbus missions to the
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
(NOAA) for its operational satellite instruments. The technology and lessons learned from the Nimbus missions are the heritage of most of the Earth-observing satellites NASA and NOAA have launched over the past three decades.
Contributions
Weather forecasting
At the time of its launch, the idea that intangible properties such as
air pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equival ...
could be observed using a satellite orbiting hundreds of miles above the Earth was revolutionary. With each Nimbus mission, scientists broadened their ability to collect
atmospheric characteristics that improved
weather forecasting
Weather forecasting is the application of science and technology to predict the conditions of the atmosphere for a given location and time. People have attempted to predict the weather informally for millennia and formally since the 19th cent ...
, including ocean and air temperatures, air pressure, and
cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...
iness. Beginning with the Nimbus 3 satellite in 1969, temperature information through the atmospheric column began to be retrieved by satellites from the eastern Atlantic and most of the Pacific Ocean, which led to significant forecast improvements. The global coverage provided by Nimbus satellites made accurate 3–5 day forecasts possible for the first time.
The ability of the Nimbus satellites to detect
electromagnetic energy
In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...
in multiple
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
s (multi-spectral data), in particular the
microwave
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...
region of the
electromagnetic spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
, made it possible for scientists to look into the atmosphere and tell the difference between
water vapor
(99.9839 °C)
, -
, Boiling point
,
, -
, specific gas constant
, 461.5 J/( kg·K)
, -
, Heat of vaporization
, 2.27 MJ/kg
, -
, Heat capacity
, 1.864 kJ/(kg·K)
Water vapor, water vapour or aqueous vapor is the gaseous p ...
and liquid water in clouds. In addition, they were able to measure atmospheric temperature even in the presence of clouds, a capability that allowed scientists to take the temperature in the "warm core" of
hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
s.
Radiation budget
One of the most important scientific contributions of the Nimbus missions was their measurements of the Earth's
radiation budget
Earth's energy budget accounts for the balance between the energy that Earth receives from the Sun and the energy the Earth loses back into outer space. Smaller energy sources, such as Earth's internal heat, are taken into consideration, but m ...
. For the first time, scientists had global, direct observations of the amount of solar radiation entering and exiting the Earth system. The observations helped to verify and refine the earliest climate models, and are still making important contributions to the study of
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. As scientists consider the causes and
effects of global warming
The effects of climate change impact the physical environment, ecosystems and human societies. The environmental effects of climate change are broad and far-reaching. They affect the water cycle, oceans, sea and land ice (glaciers), sea lev ...
, Nimbus radiation budget data provide a base for long-term analyses and make change-detection studies possible. The Nimbus technology gave rise to current radiation-budget sensors, such as the
CERES
Ceres most commonly refers to:
* Ceres (dwarf planet), the largest asteroid
* Ceres (mythology), the Roman goddess of agriculture
Ceres may also refer to:
Places
Brazil
* Ceres, Goiás, Brazil
* Ceres Microregion, in north-central Goiás ...
instruments on NASA's
Terra
Terra may often refer to:
* Terra (mythology), primeval Roman goddess
* An alternate name for planet Earth, as well as the Latin name for the planet
Terra may also refer to: Geography Astronomy
* Terra (satellite), a multi-national NASA scienti ...
and
Aqua
Aqua is the Latin word for water. It is used in many words which relate to water, such as aquatic life. In English, it may also refer to:
Arts
* Aqua (color), a greenish-blue color
Business
* Aqua (skyscraper), an 82-story residential skysc ...
satellites.
Ozone layer
Even before the Nimbus satellites began collecting their observations of Earth's
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rela ...
, scientists had some understanding of the processes that maintained or destroyed it. They were pretty sure they understood how the layer formed, and they knew from laboratory experiments that
halogen
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...
s could destroy
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
. Finally,
weather balloons had revealed that the concentration of ozone in the atmosphere changed over time, and scientists suspected weather phenomena or seasonal change were responsible. But how all of these pieces of information worked together on a global scale was still unclear.
Scientists conducted experiments from NASA experimental aircraft and proved that atmospheric chemicals such as the
chlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and prop ...
s (CFCs) released from
refrigerants and
aerosol spray
Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. It comprises a can or bottle that contains a payload, and a propellant under pressure. When the container's valve is opened, the payload is forced out ...
s did destroy ozone. As Nimbus 7 satellite observations accumulated between 1978 and 1994, it became increasingly clear that CFCs were creating an
ozone hole
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone lay ...
each winter season over
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
. Not only that, but despite some year-to-year variations, it appeared the hole was becoming larger. The Nimbus measurements made clear how severe the ozone hole problem was.
Sea ice
Nimbus satellites collected orbital data on the extent of the polar caps in the mid-1960s, recorded in the visible and infrared parts of the spectrum. These first global snapshots of Earth's icecaps provide invaluable reference points for climate change studies. During a narrowing window of opportunity for
data archaeology
There are two conceptualisations of data archaeology, the technical definition and the social science definition.
Data archaeology (also data archeology) in the technical sense refers to the art and science of recovering computer data Code, enc ...
, the
National Snow and Ice Data Center (NDISC) and NASA were able to recover data that allowed the reconstruction of high-resolution Nimbus 2 images from 1966 showing the entire Arctic and Antarctic ice caps.
When the Nimbus 5 spacecraft launched in 1972, scientists planned for its
Electrically Scanning Microwave Radiometer to collect global observations of where and how much it rained across the world. However, a new priority for the sensor evolved in the months following its launch: mapping global
sea ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
concentrations. When Nimbus 7 launched in 1978, technology had improved enough for scientists to distinguish newly formed (i.e., "first year") sea ice from older ice, with the
Scanning Multichannel Microwave Radiometer The Scanning Multichannel Microwave Radiometer (SMMR) ronounced ''simmer''was a five-frequency microwave radiometer flown on the Seasat and Nimbus 7 satellites. Both were launched in 1978, with the Seasat mission lasting less than six months until ...
(SMMR) sensor. The data it collected during its 9-year lifespan provide a significant chunk of the long-term record of Earth's
sea ice concentration
Sea ice concentration is a useful variable for climatology, climate
scientists and nautical navigators. It is defined as the area of
sea ice relative to the total at a given point in the ocean.
This article will deal primarily with its determinati ...
that today's scientists use for studies of climate change.
Among the most serendipitous discoveries that the Nimbus missions made possible was that of a gaping hole in the sea ice around Antarctica in the Southern Hemisphere winters of 1974–76. In a phenomenon that has not been observed since, an enormous, ice-free patch of water, called a
polynya
A polynya () is an area of open water surrounded by sea ice. It is now used as a geographical term for an area of unfrozen seawater within otherwise contiguous pack ice or fast ice. It is a loanword from the Russian полынья (), which re ...
, developed three years in a row in the seasonal ice that encases Antarctica each winter. Located in the
Weddell Sea
The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha ...
, each year the polynya vanished with the summer melt, but returned the following year. The open patch of water may have influenced ocean temperatures as far down as 2,500 meters and influenced ocean circulation over a wide area. The Weddell Sea Polynya has not been observed since the event witnessed by the Nimbus satellites in the mid-70s.
Global positioning system
Nimbus satellites (beginning with Nimbus 3 in 1969) blazed the trail into the modern
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
era with operational
search and rescue
Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...
and data collection systems. The satellites tested the first technology that allowed satellites to locate weather-observation stations set up in remote locations and to command the stations to transmit their data back to the satellite. The most famous demonstration of the new technology was through the record-breaking flight of British aviator
Sheila Scott
Sheila Christine Scott OBE (nee Hopkins; 27 April 1922 – 20 October 1988) was an English aviator who broke over 100 aviation records through her long distance flight endeavours, which included a "world and a half" flight in 1971. On this f ...
, who tested the Nimbus navigation and locator communication system when she made the first-ever solo flight over the
North Pole
The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Mag ...
in 1971.
The Nimbus ground-to-satellite-to-ground communication system demonstrated the first satellite-based search and rescue system. Among the earliest successes were the rescue of two
hot air balloon
A hot air balloon is a lighter-than-air aircraft consisting of a bag, called an envelope, which contains heated air. Suspended beneath is a gondola or wicker basket (in some long-distance or high-altitude balloons, a capsule), which carries ...
ists who went down in the
North Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe and ...
in 1977 and, later that year, tracking a
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
ese adventurer on his first attempt to be the first person to
dogsled
A dog sled or dog sleigh is a sled pulled by one or more sled dogs used to travel over ice and through snow. Numerous types of sleds are used, depending on their function. They can be used for dog sled racing. Traditionally in Greenland and the ...
solo to the North Pole through
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...
. Tens of thousands of people over the past three decades have been rescued through the Search and Rescue Satellite-aided Tracking (
SARSAT) operational system on NOAA satellites.
Nuclear power
Nimbus-3 was the first satellite to use a
SNAP-19
The Systems Nuclear Auxiliary POWER (SNAP) program was a program of experimental radioisotope thermoelectric generators (RTGs) and space nuclear reactors flown during the 1960s by NASA.
Odd-numbered SNAPs: radioisotope thermoelectric generators ...
radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioacti ...
(RTG) in space. A previous attempt was made to launch a SNAP-19 RTG on Nimbus-B-1, but the rocket was destroyed and the nuclear fuel landed in the
Santa Barbara Channel
The Santa Barbara Channel is a portion of the Southern California Bight and separates the mainland of California from the northern Channel Islands. It is generally south of the city of Santa Barbara, and west of the Oxnard Plain in Ventura Count ...
. Later, the fuel was recovered from the wreckage at a depth of and re-purposed for Nimbus-3 as the SNAP-19B.
This power source augmented the solar array with an additional of electrical power.
Operation history of the Nimbus satellites
See also
*
Coastal Zone Color Scanner
The coastal zone color scanner (CZCS) was a multi-channel scanning radiometer aboard the Nimbus 7 satellite, predominately designed for water remote sensing. Nimbus 7 was launched 24 October 1978, and CZCS became operational on 2 November 1978. ...
References
External links
*http://nssdc.gsfc.nasa.gov/earth/nimbus.html Nimbus Program
*http://nssdc.gsfc.nasa.gov/earth/nimbus_sensor.html Experimental Instrumentation on-board Nimbus satellites
{{Authority control
Weather satellites of the United States
Remote sensing programs
Satellite series
NASA programs