NOAA-2, also known as ITOS-D was a

weather 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 can be polar orbiting (covering the entire Earth asynchronously), or ge ...

operated by 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). It was part of a series of satellites called ITOS, or improved

TIROS TIROS, or Television InfraRed Observation Satellite, is a series of early weather satellites launched by the United States, beginning with TIROS-1 in 1960. TIROS was the first satellite that was capable of remote sensing of the Earth, enablin ...

. NOAA-2 was launched on a

Delta rocket Delta is an American versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. Japan also launched license-built derivatives ( N-I, N-II, and H-I) from 1975 to 1992. More than 300 ...

on October 15, 1972. The launch carried one other satellite: AMSAT-OSCAR 6.

Mission of NOAA-2

NOAA 2 was the first in a series of reconfigured ITOS-M satellites launched with new meteorological sensors on board to expand the operational capability of the ITOS system. NOAA 2 was not equipped with conventional TV cameras. It was the first operational

to rely solely upon radiometric imaging to obtain

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 co ...

data. The primary objective of NOAA 2 was to provide global daytime and nighttime direct readout real-time cloud cover data on a daily basis. The sun-synchronous spacecraft was also capable of supplying global

atmospheric An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

soundings and very high resolution infrared cloudcover data for selected areas in either a direct readout or a tape-recorder mode. A secondary objective was to obtain global solar-proton flux data on a real-time daily basis. The primary sensors consisted of Very High Resolution Radiometer (VHRR), a Vertical Temperature Profile Radiometer (VTPR), and a Scanning Radiometer (SR). The VHRR, VTPR, and SR were mounted on the satellite baseplate with their optical axes directed vertically earthward. The nearly cubical spacecraft measured . The satellite was equipped with three curved solar panels that were folded during launch and deployed after orbit was achieved. Each panel measured over in length when unfolded and was covered with approximately 3,500

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

s measuring . The NOAA 2 dynamics and attitude control system maintained desired spacecraft orientation through

gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotat ...

principles incorporated into the satellite design. Earth orientation of the satellite body was maintained by taking advantage of the

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In othe ...

induced from a momentum flywheel so that the satellite body precession rate of one

revolution per orbit In political science, a revolution (Latin: ''revolutio'', "a turn around") is a fundamental and relatively sudden change in political power and political organization which occurs when the population revolts against the government, typically due ...

provided the desired earth-looking attitude. Minor adjustments in attitude and orientation were made by means of

magnetic coil An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil (spiral or helix). Electromagnetic coils are used in electrical engineering, in applications where electric currents interact with magnetic fields, in de ...

s and by varying the speed of the momentum flywheel. The spacecraft operated satisfactorily until March 18, 1974, when VTPR failed. NOAA 2 was then placed in a marginal

standby mode Sleep mode (or suspend to RAM) is a low power mode for electronic devices such as computers, televisions, and remote controlled devices. These modes save significantly on electrical consumption compared to leaving a device fully on and, upon resu ...

from March 19 to July 1, 1974. It was then used as the operational NOAA satellite until October 16, 1974, when it was again placed in a marginal standby mode. The spacecraft was deactivated on January 30, 1975.

Current status

The satellite's ITOS imaging system has been heard transmitting a sync signal containing no image, on March 13, 2021, by Scott Tilley, confirmed shortly after by Derek OK9SGC and again later by Derek on September 25, 2022.

References

1972 in spaceflight Weather satellites of the United States Spacecraft launched in 1972 Spacecraft launched by Delta rockets

External links

NOAA-2 Satellite Position
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