Explorer 60, also called SAGE (Stratospheric Aerosol and Gas Experiment) and was the second of the Applications Explorer Missions (AEM), AEM-B (Applications Explorer Mission-B), was a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

scientific satellite launched on 18 February 1979, from

Wallops Flight Facility Wallops Flight Facility (WFF) is a rocket launch site on Wallops Island on the Eastern Shore of Virginia, United States, just east of the Delmarva Peninsula and approximately north-northeast of Norfolk, VA, Norfolk. The facility is operated ...

(WFF) by a Scout D-1

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

Spacecraft

Explorer 60 had a launch

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

of . The spacecraft was designed for a 1-year life in orbit. Explorer 60 was a small, versatile, and low-cost spacecraft made of two distinct parts: (1) the SAGE instrument module containing the detectors and the associated hardware, and (2) the base module containing the necessary data handling, power, communications, command, and attitude control subsystem to support the instrument mode. The base module includes the telemetry data system and a communications subsystem that makes use of a conical log spiral

S-band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the convention ...

antenna and two Very high frequency (VHF)

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 ...

Mission

The objective of the SAGE mission was to obtain stratospheric aerosol and

ozone Ozone () (or trioxygen) is an Inorganic compound, 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 , break ...

data on a global scale for a better understanding of the Earth's environmental quality and radiation budget.

Experiment

Stratospheric Aerosol and Gas Experiment (SAGE)

The objectives of the Stratospheric Aerosol and Gas Experiment (SAGE) were to determine the spatial distribution of stratospheric aerosols and ozone on a global scale. Specific objectives were (1) to develop a satellite-based remote-sensing technique for stratospheric aerosols and ozone measurements, (2) to map aerosol and ozone concentrations on a time scale shorter than major stratospheric changes, (3) to locate stratospheric aerosol and ozone sources and sinks, (4) to monitor circulation and transfer phenomena, (5) to observe hemisphere differences, and (6) to investigate the optical properties of aerosols and assess their effects on global climate. The SAGE instrument was a

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 ...

consisting of a

gregorian telescope The Gregorian telescope is a type of reflecting telescope designed by Scottish mathematician and astronomer James Gregory in the 17th century, and first built in 1673 by Robert Hooke. James Gregory was a contemporary of Isaac Newton, and both ...

and a detector subassembly which measured the attenuation of

solar radiation Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible light perceptible to the human eye as well as invisible infrared (typically p ...

at four wavelengths (0.385, 0.45, 0.6, and 1.0

micrometre The micrometre (English in the Commonwealth of Nations, 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 uni ...

) during solar occultation. As the spacecraft emerged from the Earth's shadow, the sensor scanned the

atmosphere of Earth The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather ...

from the horizon up and measured the attenuation of solar radiation by different atmospheric layers. This procedure was repeated during spacecraft sunset. Two vertical scannings were obtained during each orbit, with each scan requiring approximately 1 minute of time to cover the atmosphere above the

troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...

. The instrument had a

field of view The field of view (FOV) is the angle, angular extent of the observable world that is visual perception, seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to elec ...

of approximately 0.15

milliradian A milliradian (International System of Units, SI-symbol mrad, sometimes also abbreviated mil) is an SI derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian). Milliradians are used in adjustment of ...

which resulted in a vertical resolution of about . Spatial coverage extended from about 79°N to 79°S

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

and thus complemented the coverage (64°N to 80°N and 64°S to 80°S) of the SAM II on

Nimbus 7 Nimbus 7 (also called Nimbus G) was a meteorological satellite. It was the seventh and last in a series of the Nimbus program. Launch Nimbus 7 was launched on October 24, 1978, by a Delta rocket from Vandenberg Air Force Base, California, Un ...

. The instrument performed satisfactorily. Because of power problems, the data collection was limited to sunset events after June 1979, and was eventually terminated on 18 November 1981.

Results

Explorer 60 experienced power problems after 15 May 1979. However, the spacecraft operations continued until 19 November 1981. Explorer 60 detected and tracked also 5 volcanic eruption plumes that penetrated the

stratosphere The stratosphere () is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher ...

. It determined the amount of new material for each volcano added to the stratosphere. The signal from the spacecraft was last received on 7 January 1982, when the battery failed. On 11 April 1989, the spacecraft decayed in the atmosphere.

References