Nimbus 4 (also called Nimbus D) was a

meteorological satellite A weather satellite or meteorological satellite is a type of Earth observation satellite that is primarily used to monitor the weather and climate of the Earth. Satellites are mainly of two types: polar orbiting (covering the entire Earth asyn ...

. It was the fourth in a series of the

Nimbus program The Nimbus satellites were second-generation U.S. robotic spacecraft launched between 1964 and 1978 used for meteorology, meteorological research and development. The spacecraft were designed to serve as stabilized, Earth-oriented platforms fo ...

Launch

Nimbus 4 was launched on April 8, 1970, by a

Thor-Agena Thor-Agena was a series of orbital launch vehicles. The launch vehicles used the Douglas Aircraft Company, Douglas-built Thor (rocket family), Thor first Multistage rocket, stage and the Lockheed Corporation, Lockheed-built RM-81 Agena, Agena ...

rocket from

Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg S ...

Lompoc, California Lompoc ( ; Chumashan ) is a city in Santa Barbara County, California, United States. Located on the Central Coast, its population was 43,834 as of July 2021. Lompoc has been inhabited for thousands of years by the Chumash people, who called t ...

, United States. The spacecraft functioned nominally until September 30, 1980. The satellite orbited the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

once every 1 hour and 47 minutes, at an inclination of 80°. Its

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

was and its

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

was .

Mission

The fourth in a series of second-generation meteorological research and development satellites, Nimbus 4 was designed to serve as a stabilized, earth-oriented platform for the testing of advanced

meteorological Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agriculture ...

sensor systems, and for collecting meteorological data. The polar-orbiting spacecraft consisted of three major structures: a

torus In geometry, a torus (: tori or toruses) is a surface of revolution generated by revolving a circle in three-dimensional space one full revolution about an axis that is coplanarity, coplanar with the circle. The main types of toruses inclu ...

-shaped sensor mount, solar paddles, and the

control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial ...

housing. The solar paddles and the control system were connected to the sensor mount by a

truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so ...

structure, giving the satellite the appearance of an ocean

buoy A buoy (; ) is a buoyancy, floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. History The ultimate origin of buoys is unknown, but by 1295 a seaman's manual referred to navig ...

. Nimbus 4 was nearly tall, in diameter at the base, and about across with solar paddles extended. The torus-shaped sensor mount, which formed the satellite base, housed the

electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...

equipment and battery modules. The lower surface of the torus ring provided mounting space for sensors and

telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', 'far off', an ...

antennas In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating electric current into radio waves (transmitting), or radio waves into an electric current (receivi ...

. An H-frame structure mounted within the center of the torus provided support for the larger experiments and tape recorders. Mounted on the control system housing, which was on top of the spacecraft, were

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

sensors, horizon scanners,

gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

nozzles for attitude control, and a command antenna. Use of an advanced attitude-control subsystem permitted the spacecraft's orientation to be controlled to within plus or minus 1 degree for all three axes (pitch, roll, yaw)

Instruments

The primary experiments consisted of:Sabatini, R. (1970
''Nimbus IV User's Guide''
GSFC NASA-TM-X-69887 *

Image Dissector An image dissector, also called a dissector tube, is a video camera tube in which photocathode emissions create an "electron image" which is then swept up, down and across an anode to produce an electrical signal representing the visual image. I ...

Camera System (IDCS): for providing daytime

cloud cover Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by clouds on average when observed from a particular location. Okta is the usual unit for measurement of the cloud cover. The cloud c ...

pictures, both in real-time and recorded modes; * Temperature-Humidity

Infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

Radiometer A radiometer or roentgenometer is a device for measuring the radiant flux (power) of electromagnetic radiation. Generally, a radiometer is an infrared radiation detector or an ultraviolet detector. Microwave radiometers operate in the micro ...

(THIR): for measuring daytime and nighttime surface and cloudtop temperatures, as well as the water vapor content of the

upper atmosphere Upper atmosphere is a collective term that refers to various layers of the atmosphere of the Earth above the troposphere and corresponding regions of the atmospheres of other planets, and includes: * The mesosphere, which on Earth lies between th ...

; * Infrared

Interferometer Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

Spectrometer A spectrometer () is a scientific instrument used to separate and measure Spectrum, spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomeno ...

(IRIS): for measuring the emission spectra of the earth/atmosphere system; * Satellite

Infrared Spectrometer Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functio ...

(SIRS): for determining the vertical profiles of temperature and

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

in the atmosphere; * Monitor of

Ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

Solar Energy (MUSE): for detecting solar UV radiation; *

Backscatter In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came. It is usually a diffuse reflection due to scattering, as opposed to specular reflection as from a mirror, ...

Ultraviolet Spectrometer (BUV): for monitoring the vertical distribution and total amount of atmospheric ozone on a global scale; * Filter Wedge Spectrometer (FWS): for accurate measurement of IR radiance as a function of

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

from the earth/atmosphere system; * Selective Chopper Radiometer (SCR): for determining the temperatures of six successive layers in the atmosphere from absorption measurements in the 15

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

band; * Interrogation, Recording, and Location System (IRLS): for locating, interrogating, recording, and retransmitting meteorological and geophysical data from remote collection stations. The spacecraft performed well until April 14, 1971, when attitude problems started. The experiments continued to operate on a limited time basis until September 30, 1980.

References

Weather satellites of the United States Spacecraft launched in 1970 {{US-spacecraft-stub