|Nimbus - |
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The Nimbus Technology satellite program was initiated by NASA in the early 1960's to develop an observational system capable of meeting the research and development needs of Earth scientists. The objectives of the program were to: develop advanced passive radiometric and spectrometric sensors for surveillance of the atmosphere and oceans; develop and evaluate new active and passive sensors for sounding the atmosphere and for mapping surface characteristics; develop advanced space technology and ground data processing techniques for meteorological and scientific research; and participate in global observation programs such as the World Weather Watch (WWW). Eight spacecraft were built, of which 7 were launched, with one failure, between 1964 and 1978. The Nimbus satellites were placed in polar orbits and acquired global data twice every 24 hours.
Nimbus were second-generation meteorological research-and-development satellites that was designed to serve as a stabilised, earth-oriented platform for the testing of advanced meteorological sensor systems and for collecting meteorological data. The polar-orbiting spacecraft consisted of three major elements: (1) a sensory ring, (2) solar paddles, and (3) the control system housing. The solar paddles and the control system housing were connected to the sensory ring by a truss structure, giving the satellite the appearance of an ocean buoy. Nimbus, depending on the experiments carried, was 3.04 to 3.7 m tall, 1.52 m in diameter at the base, and 3 to 3.96 m across with solar paddles extended. The sensory ring, which formed the satellite base, housed the electronics equipment and battery modules. The lower surface of the torus-shaped sensory ring provided mounting space for sensors and telemetry antennas. An H-frame structure mounted within the centre of the torus provided support for the larger experiments and tape recorders. Mounted on the control system housing, which was located on top of the spacecraft, were sun sensors, horizon scanners, gas nozzles for attitude control, and a command antenna. Use of a stabilisation and control system allowed the spacecraft's orientation to be controlled to within plus or minus 1 degree for all three axes (pitch, roll, and yaw). Sensors carried varied by mission.
Total Mass: 907 kg.
Returned 27,000 cloud cover images. The spacecraft carried an advanced vidicon camera system for recording and storing remote cloudcover pictures, an automatic picture transmission camera for providing real-time cloud cover pictures, and a high-resolution infrared radiometer to complement the daytime TV coverage and to measure nighttime radiative temperatures of cloud tops and surface terrain. A short second-stage burn resulted in an unplanned eccentric orbit. Otherwise, the spacecraft and its experiments operated successfully until September 22, 1964. The solar paddles became locked in position, resulting in inadequate electrical power to continue operations.
TV, IR cloud cover photos. The spacecraft carried an advanced vidicon camera system for recording and storing remote cloud cover pictures, an automatic picture transmission camera for providing real-time cloudcover pictures, and both high- and medium-resolution infrared radiometers (HRIR and MRIR) for measuring the intensity and distribution of electromagnetic radiation emitted by and reflected from the earth and its atmosphere. The spacecraft and experiments performed normally after launch until July 26, 1966, when the spacecraft tape recorder failed. Its function was taken over by the HRIR tape recorder until November 15, 1966, when it also failed. Some real-time data were collected until January 17, 1969, when the spacecraft mission was terminated owing to deterioration of the horizon scanner used for earth reference.
Launched with Secor 10.
Credit: NASA. 25,610 bytes. 341 x 373 pixels.
Environmental research. Primary experiments consisted of an image dissector camera system for providing daytime cloudcover pictures both in real-time and recorded modes, temperature-humidity infrared radiometer (THIR) for measuring daytime and nighttime surface and cloudtop temperatures as well as the water vapor content of the upper atmosphere, infrared interferometer spectrometer (IRIS) for measuring the emission spectra of the earth/atmosphere system, satellite infrared spectrometer (SIRS) for determining the vertical profiles of temperature and water vapor in the atmosphere, a monitor of ultraviolet solar energy (MUSE) for detecting solar UV radiation, a backscatter ultraviolet (BUV) detector for monitoring the vertical distribution and total amount of atmospheric ozone on a global scale, a filter wedge spectrometer (FWS) for accurate measurement of IR radiance as a function of wavelength from the earth/atmosphere system, a selective chopper radiometer (SCR) for determining the temperatures of six successive 10-km layers in the atmosphere from absorption measurements in the 15-micrometer CO2 band, and an 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 then operated on a limited time basis until September 30, 1980.
Environmental research. Primary experiments included a temperature-humidity infrared radiometer (THIR) for measuring day and night surface and cloudtop temperatures as well as the water vapor content of the upper atmosphere, electrically scanning microwave radiometer (ESMR) for mapping the microwave radiation from the earth's surface and atmosphere, infrared temperature profile radiometer (ITPR) for obtaining vertical profiles of temperature and moisture, Nimbus E microwave spectrometer (NEMS) for determining tropospheric temperature profiles, atmospheric water vapor abundances, and cloud liquid water contents, selective chopper radiometer (SCR) for observing the global temperature structure of the atmosphere, and a surface composition mapping radiometer (SCMR) for measuring the differences in the thermal emission characteristics of the earth's surface.
Environmental research. The experiments selected for Nimbus-6 were the earth radiation budget (ERB), electrically scanning microwave radiometer (ESMR), high-resolution infrared radiation sounder (HIRS), limb radiance inversion radiometer (LRIR), pressure modulated radiometer (PMR), scanning microwave spectrometer (SCAMS), temperature-humidity infrared radiometer (THIR), tracking and data relay experiment (T+DRE), and the tropical wind energy conversion and reference level experiment (TWERLE). This complement of advanced sensors was capable of mapping tropospheric temperature, water vapor abundance, and cloud water content; providing vertical profiles of temperature, ozone, and water vapor; transmitting real-time data to a geostationary spacecraft (ATS 6); and yielding data on the earth's radiation budget.
Environmental research. The experiments carried were a limb infrared monitoring of the stratosphere (LIMS), stratospheric and mesopheric sounder (SAMS), coastal-zone color scanner (CZCS), stratospheric aerosol measurement (SAM II), earth radiation budget (ERB), scanning multichannel microwave radiometer (SMMR), solar backscatter UV and total ozone mapping spectrometer (SBUV/TOMS), and temperature-humidity infrared radiometer (THIR). These sensors were capable of observing several parameters at and below the mesospheric levels. After 11 years in orbit, three experiments, SAM II, SBUV/TOMS, and ERB, were still functioning successfully.