Earth radiation budget experiment-
An instrument package flown on Earth Radiation Budget Satellite (launched October 1984), and also on the NOAA-9 and -10 polar-orbiting satellites (launched December 1984 and September 1986, respectively). ERBE consists of separate scanning and nonscanning instruments that were designed to determine the monthly average radiation budget on regional, zonal, and global scales. An earlier earth radiation budget instrument
was flown on Nimbus-6 and -7 (launched June 1975 and October 1978).
Earth resources technology satellite-
A sun-synchronous polar-orbiting satellite designed for remote sensing and mapping of land areas.
(Launched in July 1972, the satellite was renamed Landsat-1).
Ebert ion counter-
An instrument in which the free airstream flows between polarized condenser plates that
attract and capture ions of opposite sign (used for the measurement of the concentration and mobility of small ions in the atmosphere).
Echo box-
A type of electronic instrument used to test and adjust radar equipment. It operates on the principle of a cavity resonator. A small amount of electromagnetic energy from the transmitting antenna is fed into a small cavity (or box), the volume of which can be adjusted to resonate electrically, or “ring,” to signals of this frequency, like a tuning fork responding to a musical note of proper pitch. This resonance is detected by the radar receiver. The amount of resonance appearing at the receiver output (the oscilloscope) is a function of the power transmitted, the tuning of the cavity, and the tuning and amplification of the receiver. Accordingly, the echo
box provides a test of the overall efficiency of the radar system, eliminating atmospheric variables.
Echo sounder-
A device that uses sound waves to measure the depth of surface water bodies.
Eight inch rain gauge-
A nonrecording cylindrical rain gauge with a collector diameter of 20.3 cm (8 in.). The rain drains into a collector tube that amplifies the depth by a factor of 10.
Ejection chamber-
The chamber that houses dropsonde equipment just prior to and during release from an aircraft (a similar piece of equipment is the dropsonde dispenser).
Electrical hygrometer-
A hygrometer that uses a transducing element with electrical properties that are a function of atmospheric water vapor content (examples of such a transducer are the humidity strip, the carbon-film hygrometer element, thin-film capacitors, aluminium oxide humidity elements, and goldbeater's skin hygrometers).
Electrical substitution radiometer-
A radiometer for which the output of the thermal detector is measured as the detector is alternately exposed to a radiant energy source and then to a known internal electrical heating (radiant heating per unit area of an entrance aperture is then equated to the electrical energy used to equivalently heat the detector).
Electrical thermometer-
A thermometer that uses a transducing element with electrical properties that are a function of its thermal state (common meteorological examples of such thermometers are the resistance thermometer and the thermoelectric or thermocouple thermometer).
Electrolytic strip-
A flat plastic strip bounded by electrodes on two sides and coated with a hygroscopic chemical compound such as lithium
chloride (the electrical resistance of this coating is a function of the amount of moisture
absorbed from the atmosphere and the temperature of the strip).
Electromagnetic acoustic probe-
A device tested in the late 1950s and 1960s that used acoustic waves to create clear-air targets for a continuous-wave radar.
Electron capture detection-
A detector used in a gas chromatograph that operates by sensing a decrease in the number of free electrons in the detector cavity due to their capture by electrophilic compounds eluting from the column of the chromatograph.
Electroscope-
A general name for instruments that detect the presence of (but do not necessarily measure)
small electrical charges by electrostatic means.
Electrostatic precipitator-
A device for removing particulate matter from smokestack exhaust gas by imparting an electric charge to the particles and then attracting them to a metal plate or screen of opposite charge before the gas is exhausted out of the top of the stack.
Emanometer-
An instrument for the measurement of the radon content of the atmosphere; radon is removed from a sample of air by condensation or absorption on a surface, and is then placed in an ionization chamber and its activity determined.
Environmental chambers-
Large reactors, usually made of glass or polytetrafluoroethylene (PTFE) film,
in which gas-phase chemical reactions are carried out to simulate changes occurring in the atmosphere (either natural sunlight or artificial ultraviolet lighting can be used to initiate the chemistry; the buildup of products such as nitrogen dioxide and ozone is monitored using techniques such as gas chromatography or infrared spectroscopy).
European remote sensing satellites-
A series of satellites designed to study the earth's land, atmosphere, and oceans. The major instruments on ERS are an active microwave instrument, a radar altimeter, and an along-track scanning radiometer. The active microwave instrument operates in three modes: SAR image mode, SAR wave mode, and wind scatterometer mode. The scanning radiometer is made up of two instruments, an infrared radiometer and a microwave sounder.
ERS-2 also has a global ozone monitoring experiment. ERS-1 was launched in 1991 and ERS-2 in 1995. Both satellites operate in sun-synchronous, near-polar orbits.
Evaporimeter-
A class of evaporation gauges, which includes evaporation pans and atmometers,
that measure evaporation from free-standing water or a thoroughly wetted surface.
Expendable bathythermograph-
A device for obtaining a record of temperature as a function of depth to 1800 m from a ship with a speed as high as 15 m s-1. Temperature is measured with a thermistor within an expendable casing. Depth is determined by a prior knowledge of the rate at which the casing sinks and the time of each recorded data value. A fine wire provides a data transfer line to the ship for shipboard recording. Airborne versions (AXBT) are also used;
these use radio frequencies to transmit the data to the aircraft during deployment.
