Nimbus 3 SATELLITE: Nimbus 3 (Launched on 1969-04-14 at 07:54:00 UTC) DESCRIPTION: Nimbus 3, the third in a series of second-generation meteorological research-and-development satellites, was designed to serve as a stabilized, earth-oriented platform for the testing of advanced meteorological sensor systems and the collecting of 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 attitude control subsystem (ACS) permitted the spacecraft's orientation to be controlled to within plus or minus 1 deg for all three axes (pitch, roll, and yaw). Primary experiments consisted of (1) a satellite infrared spectrometer (SIRS) for determining the vertical temperature profiles of the atmosphere, (2) an infrared interferometer spectrometer (IRIS) for measuring the emission spectra of the earth-atmosphere system, (3) both high- and medium-resolution infrared radiometers (HRIR and MRIR) for yielding information on the distribution and intensity of infrared radiation emitted and reflected by the earth and its atmosphere, (4) a monitor of ultraviolet solar energy (MUSE) for detecting solar UV radiation, (5) an image dissector camera system (IDCS) for providing daytime cloudcover pictures in both real-time mode, using the real time transmission system (RTTS), and tape recorder mode, using the high data rate storage system, (6) a radioisotope thermoelectric generator (RTG), SNAP-19, to assess the operational capability of radioisotope power for space applications, and (7) an interrogation, recording and location system (IRLS) experiment designed to locate, interrogate, record, and retransmit meteorological and geophysical data from remote collection stations. Nimbus 3 was successful and performed normally until July 22, 1969, when the IRIS experiment failed. The HRIR and SIRS experiments were terminated on January 25, 1970, and June 21, 1970, respectively. The remaining experiments continued operation until September 25, 1970, when the rear horizon scanner failed. All spacecraft operations were terminated on January 22, 1972. More detailed information can be found in "The Nimbus III User's Guide" (TRF B03409), available from NSSDC. EXPERIMENT: High-Resolution Infrared Radiometer PI: Cherrix DESCRIPTION: The Nimbus 3 High-Resolution Infrared Radiometer (HRIR) was designed (1) to map the earth's nighttime cloud cover and thus to complement the daytime television (AVCS) coverage and (2) to measure the radiative temperatures of cloud tops and surface terrain. The Nimbus 3 HRIR was a modified version of previous experiments on Nimbus 1 and 2. It used a dual band-pass filter which transmitted reflected solar radiation in the 0.7- to 1.3-micrometer band as well as emitted thermal radiation in the 3.4- to 4.2-micrometer band. By detecting reflected solar radiation in the 0.7- to 1.3-micrometer band, the radiometer could also map the earth's cloud cover during the daytime. Radiant energy from the earth was collected by a flat scanning mirror inclined at 45 deg to the optical axis. The mirror rotated at 48 rpm and scanned in a plane normal to the spacecraft velocity. Using the direct readout infrared radiometer (DRIR) system, nighttime and daytime data could be transmitted by the real-time transmission system (RTTS) to ground APT stations. A ground resolution of 8.5 km could be obtained at nadir. The HRIR measured radiance temperatures between 210 and 330 deg K to a general accuracy of 1 deg K. For a more detailed description, see Section 3 of "The Nimbus III User's Guide" (TRF B03409). The experiment was successful until August 1969, when noise in the tape recorder system gradually reduced the quality of the data. Routine processing of HRIR data was terminated after January 31, 1970. All experiment operations ceased on January 22, 1972. The HRIR world montages were presented in "The Nimbus III Data Catalog" (TRF B06523), available from NSSDC. 1.HRIR Nighttime (3.4 to 4.2 Micron) Photofacsimile Film Strips NSSDC ID 69-037A-02A Media Information: 3235 70-mm Black & White Negative, Feet Time Span: 1969-04-22 to 1970-01-31 (as determined by NSSDC) Description: This data set consists of nighttime High Resolution Infrared Radiometer (HRIR) data on 70-mm photofacsimile film strips. The data were measured at 3.4 to 4.2 micrometers. The film strips are uniform or variable density exposure, positive or negative copies, in either a transparency or paper print. The variable density exposure film strips were produced with enhanced contrast, while the uniform density exposure film strips are true copies of the archived HRIR film strips. Each film strip is gridded with geographic coordinates and is identified by orbit number and time. For a complete description of the photofacsimile film strips, see section 3.4.1 in "The Nimbus III User's Guide," available from NSSDC. 2.HRIR Daytime (0.7 to 1.3 Micron) Photofacsimile Film Strips NSSDC ID 69-037A-02B Media Information: 2983 70-mm Black & White Negative, Feet Time Span: 1969-04-22 to 1970-01-31 (as determined by NSSDC) Description: This data set consists of daytime High Resolution Infrared Radiometer (HRIR) data on 70-mm photofacsimile film strips. The data were measured at 0.7 to 1.3 micrometers. The film strips are uniform or variable density exposure, positive or negative copies, in either a transparency or paper print. The variable density exposure film strips were produced with enhanced contrast, while the uniform density exposure film strips are true copies of the archived HRIR film strips. Each film strip is gridded with geographic coordinates and is identified by orbit number and time. For a complete description of the photofacsimile film strips, see section 3.4.1 in "The Nimbus III User's Guide," available from NSSDC. 3.HRIR Meteorological Radiation Tapes NSSDC ID 69-037A-02C Media Information: 1015 Digital Magnetic Tape Time Span: 1969-04-17 to 1970-03-21 (as determined by NSSDC) Description: This radiance data set consists of 7-track, 800-bpi, binary magnetic tapes that were generated on an IBM 360 computer. It contains daytime radiation values measured at 0.7 to 1.3 micrometers and nighttime values at 3.4 to 4.2 micrometers. The first record of each orbit contains information about the orbit. Subsequent records contain radiation values, location, and time of each observation. The format of this data set is given in section 3.5 of "The Nimbus III User's Guide." 4.Nimbus 3 Data Catalogs on Microfiche NSSDC ID 69-037A-02D Media Information: 55 4x6 in. Black & White Microfiche Time Span: 1969-04-14 to 1970-05-31 (as determined by NSSDC) Description: This data set consists of a series of catalogs that pictorially describe and index the data from the Nimbus 3 HRIR experiment. These volumes, which compose "The Nimbus III Data Catalog," cover the following periods: vol 1, April 14 to May 31, 1969; vol 2, June 1969; vol 3, July 1969; vol 4, August 1969; vol 5, September 1 to December 31, 1969; and vol 6 (final), January 1 to May 31, 1970. HRIR montages, which are presented in section 4 of the first five volumes (section 5 in vol 1), include both daytime (0.7 to 1.3 micrometer) and nighttime (3.4 to 4.2 micrometer) coverage. These photographs are arranged in chronological order in a world montage format. Key latitudes can be read by using a superimposed grid contained in each volume. Complete descriptions of the HRIR experiment and of available data are contained in section 3 of "The Nimbus III User's Guide," which should be used in conjunction with the data catalog. EXPERIMENT: Infrared Interferometer Spectrometer PI: Hanel DESCRIPTION: The Nimbus 3 Infrared Interferometer Spectrometer (IRIS) experiment was designed to provide information on the vertical structure of the atmosphere and the emissive properties of the earth's surface by measuring the surface and atmospheric radiation in the 5.0- to 20-micrometer band using a modified Michelson interferometer. Incoming radiation was reflected into the instrument from a plane mirror. The radiation was split into two beams that recombined and interfered after reflection on a fixed mirror and a moving Michelson mirror. The recombined beam was then focused on a bolometer detector. Interference effects resulted from the optical path difference between the two beams as the mirror moved. The moving mirror traveled about 2 mm in 11 s to give an interferogram which was recorded on magnetic tape. The interferograms were transmitted to an acquisition station, where a Fourier transform was performed to produce a thermal emission spectrum of the earth. From these spectra, vertical profiles of temperature, water vapor, and ozone, as well as other parameters of meteorological interest, could be derived. The instrument had a field of view equivalent to a 144-km diameter circle on the surface of the earth at a planned orbital height of 1100 km. For a more detailed description, see Section 5 of "The Nimbus III User's Guide" (TRF B03409). The experiment was successful, and good data were obtained until the instrument failed on July 22, 1969. 1.Infrared Interferometer Spectrometer (IRIS) Archival Tapes NSSDC ID 69-037A-03A Media Information: 102 Digital Magnetic Tapes Time Span: 1969-04-15 to 1969-07-01 (as determined by NSSDC) Description: This set of radiation data was originally generated on an IBM 360 computer onto 9-track, 1600-bpi, binary tapes. The tapes contain thermal emission spectra of the earth's atmosphere system. The spectra were obtained from Fourier transformed interferograms with wave numbers between 400 and 2000 reciprocal cm and have a nominal spectral resolution of 5 reciprocal cm. The tapes also contain documentation information, reference calibration, average instrument temperature, calibrated atmospheric spectrum, and a summary for each orbital pass. Ninety degrees have been added to all latitude values to eliminate negative signs. A more complete description of the IRIS archival tapes appears in section 5 of "The Nimbus III User's Guide," available from NSSDC. EXPERIMENT: Satellite Infrared Spectrometer (SIRS) PI: Wark DESCRIPTION: The Nimbus 3 Satellite Infrared Spectrometer (SIRS) experiment was designed to indirectly determine the vertical temperature profiles of the atmosphere by measuring the infrared radiation emitted from the earth and its atmosphere in seven spectral intervals in the carbon dioxide band (11 to 15 micrometers) and one interval in the atmospheric window centered at 11.1 micrometers. The main components of the Fastie-Ebert fixed-grating spectrometer consisted of (1) a plane, light-collecting mirror to provide a single earth-viewing beam fixed in the vertical, (2) a rotating chopper mirror, (3) a spherical mirror, (4) a 12.7-cm diffraction grating with 1250 lines per inch, (5) a set of eight exit slits with a single interference filter, (6) eight wedge-immersed thermistor bolometers, (7) a blackbody radiation source for calibration, and (8) eight preamplifiers and eight operational amplifiers. The incoming radiation was chopped, spectrally dispersed by the diffraction grating, focused on the exit slits as a spectrum by the spherical mirror, and converted to electrical signals. The signals were then amplified and stored on magnetic tape for subsequent playback to a ground acquisition station. The instrument field of view was 11.5 by 11.5 deg centered on nadir. This provided data over an area roughly 220 km on a side at a satellite height of 1100 km. Data from the 11.1-micrometer channel yielded surface and/or cloudtop temperatures. Data from the carbon dioxide band could be used to generate temperature-pressure profiles by a mathematical inversion technique. The resulting temperatures had rms errors slightly less than 1 deg C. For a more detailed description, see Section 6 of "The Nimbus III User's Guide" (TRF B03409). The SIRS experiment was successful and good data were obtained. On June 21, 1970, the experiment was turned off and all data acquisition effort was transferred to the SIRS experiment on Nimbus 4. 1.SIRS Radiance Values on Tape NSSDC ID 69-037A-04A Media Information: 6 Restored Tapes Time Span: 1969-04-14 to 1970-06-19 (as determined by NSSDC) Description: This data set contains radiance values that were generated on a CDC 6600 computer onto binary magnetic tapes. The first record of each orbit contains information identifying the orbit and a summary of the instrument status throughout the orbit. The following records contain the radiance values along with calibration data, latitude, longitude, and time of each observation. For a more complete description of the tape format and a discussion of the data quality, see vol. 1 of both "The Nimbus III User's Guide" and "The Nimbus III Data Catalog." A set of derived temperature profiles is available from the National Climatic Data Center, Asheville, North Carolina. EXPERIMENT: Medium-Resolution Infrared Radiometer PI: McCulloch DESCRIPTION: The Nimbus 3 Medium-Resolution Infrared Radiometer (MRIR) experiment measured the intensity and distribution of the electromagnetic radiation emitted by and reflected from the earth and its atmosphere in five selected wavelength intervals from 0.2 to 23 micrometers. Data on the heat balance of the earth-atmosphere system were obtained as well as water vapor distribution data, surface or near-surface temperatures, and data on seasonal changes of stratospheric temperature distribution. The five wavelength regions were (1) the 6.5- to 7.0-micrometer channel, which covered the 6.7-micrometer water vapor absorption band, (2) the 10- to 11-micrometer band, which operated in the atmospheric window, (3) the 14.5- to 15.5-micrometer band, which covered the 15-micrometer carbon dioxide absorption band, (4) the 20- to 23-micrometer channel, which covered the spectral region containing the broad rotational absorption bands of water vapor, and (5) the 0.2- to 4.0-micrometer channel, which yielded information on the intensity of reflected solar energy. Radiant energy from the earth was collected by a flat scanning mirror inclined at 45 deg to the optical axis. The mirror rotated at 8 rpm and scanned in a plane perpendicular to the direction of motion of the satellite. Each of the five channels contained a 4.33-cm diameter folded telescope with a 2.8-deg field of view and a thermistor bolometer. At a satellite altitude of 1100 km, a horizontal resolution of 45 km was obtained. The MRIR experiment was successful, in spite of a telemetry conflict that caused the experiment to be periodically turned off. During August and September 1970 (hurricane season), the MRIR was on essentially full time to cover the area from the equator to 70 deg N and from 10 deg E to 100 deg W. On September 25, 1970, the satellite's rear horizon scanner failed, making it impossible to determine where the MRIR sensor was pointing. The experiment was operated periodically until January 22, 1972, when all spacecraft operations were terminated. 1.MRIR Photofacsimile Films NSSDC ID 69-037A-05A Media Information: 3962 70-mm Black & White Negative, Feet Time Span: 1969-04-14 to 1970-02-05 (as determined by NSSDC) Description: This set of photofacsimile film strips is available as 4- by 5-in. positive or negative film transparencies or positive paper prints. Data measured by 5 channels (6.5-7.0, 10-11, 14.5-15.5, 20-23, and 0.2-4.0 micrometers) are displayed along with gridding, time, and a calibration gray-scale strip. Prints of these photofacsimile data are contained in data set 69-037A-05C. 2.MRIR Meteorological Radiation Tapes NSSDC ID 69-037A-05B Media Information: 20 Restored Tapes Time Span: 1969-04-15 to 1970-02-04 (as determined by NSSDC) Description: The Medium-Resolution Infrared Radiometer (MRIR) data are on binary magnetic tapes called Nimbus Meteorological Radiation Tapes (NMRT-MRIR). They contain radiances measured at 6.4-6.9, 10-11, 14-16, 5-30, and 0.2-4.0 micrometers. The latitude, longitude, time, and other orbital and telemetry data are also included. There is one file for each orbit of data. The first record in each file contains the documentation for the succeeding data records. The format of the tapes can be found in section 4 of "The Nimbus III User's Guide." 3.Nimbus 3 Data Catalogs on Microfiche NSSDC ID 69-037A-05C Media Information: 62 4x6 in. Black & White Microfiche Time Span: 1969-04-14 to 1970-05-31 (as determined by NSSDC) Description: This data set consists of a six-volume catalog called "The Nimbus III Data Catalog." It pictorially describes and indexes the data from the Nimbus 3 Medium-Resolution Infrared Radiometer (MRIR) experiment. The data catalog covers the following periods: vol 1, April 14 to May 31, 1969; vol 2, June 1969; vol 3, July 1969; vol 4, August 1, 1969; vol 5, September 1 to December 31, 1969; and vol 6, January 1 to May 31, 1970. The MRIR pictorial data are presented in section 5 of each volume. These photographs are available from NSSDC as 4- by 5-in. negatives (see data set 69-037A-05A.) Complete descriptions of the MRIR experiment and of available data are contained in section 4 of "The Nimbus III User's Guide," which should be used in conjunction with the data catalog. EXPERIMENT: Image Dissector Camera System (IDCS) PI: Branchflower DESCRIPTION: The Nimbus 3 Image Dissector Camera System (IDCS) was designed to take daytime cloudcover photographs. The pictures could be transmitted to APT stations using the real-time transmission system (RTTS) or stored on magnetic tape for subsequent playback to ground acquisition stations. The camera was mounted on the bottom of the satellite sensory ring and pointed vertically down toward the earth at all times. The image dissector was a shutterless electronic scan and step tube mounted behind a wide-angle (108 deg), 5.7-mm focal length lens. Scanning and stepping functions occurred continuously while the satellite progressed along its orbital path. The field of view of the optics was 73.6 deg in the direction of flight and 98.2 deg in a plane normal to the direction of flight. The image was focused by the optics on a photosensitive surface of the image dissector tube. A line-scanning beam scanned the photosensitive surface at 4 Hz with a frame period of 200 s. At the nominal spacecraft altitude of 1100 km, each resulting picture was approximately 1400 km on a side, with a ground resolution of 3 km at nadir. For a more detailed description, see Section 2 of "The Nimbus III User's Guide" (TRF B03409). The experiment was a success and produced good data until September 25, 1970, when operations were terminated owing to spacecraft yaw problems. Data from this experiment are available through SDSD. The IDCS world montages were presented in "The Nimbus III Data Catalog" (TRF B06523), available from NSSDC. 1.Nimbus 3 Data Catalogs on Microfiche NSSDC ID 69-037A-06A Media Information: 51 4x6 in. Black&White Microfiche Time Span: 1969-04-14 to 1970-05-31 (as determined by NSSDC) Description: This catalog contains black and white pictorial montages from the Nimbus 3 Image Dissector Camera System (IDCS). These montages consist of miniature reproductions of daily, daytime pictures and are made up of adjacent swaths of data from successive orbits. The satellite orbit number is printed below each swath. A transparent grid overlay provides geographic reference. The catalog consists of six volumes: vol 1, April 14 to May 31, 1969; vol 2, June 1969; vol 3, July 1969; vol 4, August 1969; vol 5, September 1 to December 31, 1969; and vol 6, January 1 to May 31, 1970. However, IDCS montages are only contained in the first five volumes. This catalog does not contain background information on the spacecraft or experiment, nor is there a description of the techniques used in processing the data. Such information is contained in "The Nimbus III User's Guide," which should be used with this catalog when ordering data. Nimbus 4 SATELLITE: Nimbus 4 (Launched on 1970-04-08 at 08:17:00 UTC) DESCRIPTION: Nimbus 4, the fourth in a series of second-generation meteorological research-and-development satellites, was designed to serve as a stabilized, earth-oriented platform for the testing of advanced meteorological sensor systems, and for collecting meteorological data. The polar-orbiting spacecraft consisted of three major structures: (1) a ring-shaped sensor mount, (2) solar paddles, and (3) the control system housing. Use of an advanced attitude-control subsystem permitted the spacecraft's orientation to be controlled to within plus or minus 1 deg for all three axes (pitch, roll, and yaw). Primary experiments consisted of (1) an image dissector camera system (IDCS) for providing daytime cloudcover pictures, both in real-time and recorded modes, (2) a 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, (3) an infrared interferometer spectrometer (IRIS) for measuring the emission spectra of the earth/atmosphere system, (4) a satellite infrared spectrometer (SIRS) for determining the vertical profiles of temperature and water vapor in the atmosphere, (5) a monitor of ultraviolet solar energy (MUSE) for detecting solar UV radiation, (6) a backscatter ultraviolet (BUV) detector for monitoring the vertical distribution and total amount of atmospheric ozone on a global scale, (7) a filter wedge spectrometer (FWS) for accurate measurement of IR radiance as a function of wavelength from the earth/atmosphere system, (8) 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 (9) an interrogation, recording, and location system (IRLS) for locating, interrogating, recording, and retransmitting meteorological and geophysical data from remote collection stations. A complete description can be found in "The Nimbus IV User's Guide" (TRF B06861), available from NSSDC. The spacecraft performed well until April 14, 1971, when attitude problems started. The experiments operated on a limited time basis after that time until September 30, 1980. EXPERIMENT: Temperature-Humidity Infrared Radiometer (THIR) PI: McCulloch DESCRIPTION: The Nimbus 4 THIR was designed to detect emitted thermal radiation in both the 10.5- to 12.5-micrometer region (IR window) and the 6.5- to 7.0-micrometer region (water vapor). The window channel measured cloudtop temperatures day and night. The other channel operated primarily at night to map the water vapor distribution in the upper troposphere and stratosphere. The instrument consisted of a 12.7-cm Cassegrain system, a scanning mirror common to both channels, a beam splitter, filters, and two germanium-immersed thermistor bolometers. Incoming radiant energy was collected by a flat scanning mirror inclined at 45 deg to the optical axis. The mirror rotated through 360 deg at 48 rpm and scanned in a plane normal to the spacecraft velocity vector. The energy was then focused into a dichromatic beam splitter, which divided the energy spectrally and spatially into two channels. Both channels of the THIR sensor transformed the received radiation into an electrical (voltage) output with an information bandwidth of 0.5 to 360 Hz for the 10.5 to 12.5 micrometer channel and 0.5 to 120 Hz for the water vapor channel. At a nominal spacecraft altitude, the window channel had a ground resolution of about 7 km and the water vapor channel about 22 km at nadir. The THIR was initially successful but failed on January 11, 1971 (orbit 3731). It was restarted several times thereafter for very short periods of time before it finally ceased all operations in August 1971. A similar experiment was flown on Nimbus 5, 6 and 7. 1.THIR 11.5-Micron Photofacsimile Film Strips NSSDC ID 70-025A-02A Media Information: 8049 70-mm Black & White Negative, Feet Time Span: 1970-04-18 to 1971-04-08 (as determined by NSSDC) Description: These montages of brightness temperatures, measured at 11.5 micrometers, are available on 70-mm photofacsimile film strips. Positive or negative copies of the film strips are available in uniform density exposure in either transparencies or paper prints. Daytime and nighttime orbital swaths are displayed in strips, each corresponding to a distance approximately from pole to pole and a width from horizon to horizon. The ground resolution of 7.7 km at nadir decreases as the horizontal distance from the subsatellite track increases. Each film strip is gridded with geographic coordinates and is identified by orbit number, time, and an indication of whether it is daytime (D) or nighttime (N). The strips are arranged chronologically on 100- to 500-ft rolls of film. Additional descriptions of the data can be found in section 3.4.1 of "The Nimbus IV User's Guide" (TRF B06861) and in "The Nimbus 4 Data Catalog," NSSDC ID 70-025A-02C (TRF B06582.) 2.THIR 6.7-Micron Photofacsimile Film Strips NSSDC ID 70-025A-02B Media Information: 4419 70-mm Black & White Negative, Feet Time Span: 1970-04-18 to 1971-04-08 (as determined by NSSDC) Description: These montages of brightness temperatures, measured at 6.7 micrometers, are available on 70-mm photofacsimile film strips. Positive or negative copies of the film strips are available in uniform density exposure in either transparencies or paper prints. Daytime and nighttime orbital swaths are displayed in strips, each corresponding to a distance approximately from pole to pole and a width from horizon to horizon. The ground resolution of 22.6 km at nadir decreases as the horizontal distance from the subsatellite track increases. Each film strip is gridded with geographic coordinates and is identified by orbit number, time, and an indication of whether it is daytime (D) or nighttime (N). The strips are arranged chronologically on 100- to 500-ft rolls of film. Additional descriptions can be found in section 3.4.1 of "The Nimbus IV User's Guide" (TRF B06861) and in "The Nimbus 4 Data Catalog," NSSDC ID 70-025A-02C (TRF B06582.) 3.THIR Data Catalogs on Microfiche NSSDC ID 70-025A-02C Media Information: 48 4x6 in. Black & White Microfiche Time Span: 1970-04-18 to 1971-04-08 (as determined by NSSDC) Description: This data set consists of a series of volumes called "The Nimbus 4 Data Catalog." It pictorially describes data that are acquired by the IDCS and the THIR experiments. World montages are arranged in chronological order in each volume, which also includes superimposed grids for reading key latitudes. The 8-volume catalog covers the period April 1970 to April 1972. This data set should be used in conjunction with "The Nimbus IV User's Guide," TRF B06861. 4.11.5-Micron THIR Radiation Tapes NSSDC ID 70-025A-02D Media Information: 1293 Digital Magnetic Tape Time Span: 1970-04-10 to 1971-02-13 (as determined by NSSDC) Description: This set of brightness temperatures is available on 7-track, 800-bpi, binary magnetic tapes. These tapes, also referred to as Nimbus Meteorological Radiation Tapes (NMRT-THIR), are produced on an IBM 360 computer and contain one orbit of data per file. The first record of each file contains documentation and information describing the orbit. Subsequent records contain brightness temperatures that are measured at 11.5 micrometers with a ground resolution of 7.7 km. There are also locations and time of each observation. 5.6.7-Micron THIR Radiation Tapes NSSDC ID 70-025A-02E Media Information: 1032 Digital Magnetic Tape Time Span: 1970-04-14 to 1971-03-25 (as determined by NSSDC) Description: This set of brightness temperatures is available on 7-track, 800-bpi, binary magnetic tapes. These tapes, also referred to as Nimbus Meteorological Radiation Tapes (NMRT-THIR), are produced on an IBM 360 computer and contain one orbit of data per file. The first record of each file contains documentation and information describing the orbit. Subsequent records contain brightness temperatures that are measured at 6.7 micrometers with a ground resolution of 22.6 km. There are also locations and time of each observation. EXPERIMENT: Satellite Infrared Spectrometer (SIRS) PI: Wark DESCRIPTION: The Nimbus 4 SIRS experiment was designed to determine the vertical temperature and water vapor profiles of the atmosphere by using a Fastie-Ebert fixed-grating spectrometer. The instrument measured the infrared radiation (11 to 36 micrometers) emitted from the earth and its atmosphere in 13 selected spectral intervals in the carbon dioxide and water vapor bands plus one channel in the 11-micrometer atmospheric window. The main components of the spectrometer consisted of (1) a plane, light-collecting mirror to provide one fixed and two variable earth-viewing angles, (2) a rotating chopping mirror that served alternately to collect space radiation and earth radiation, (3) a 2.5-in. diffraction grating with 1250 lines per inch, (4) 14 slits with associated interference filters, (5) 14 thermistor bolometers, and (6) a blackbody source for calibration purposes. The SIRS used a scan mirror to observe 12.5 deg to either side of the subsatellite track. The field of view directly below the SIRS was approximately 215 sq km. The carbon dioxide band radiation data were transformed to a temperature profile by a mathematical inversion technique. By a similar technique, this information could then be combined with the water vapor band data to obtain a water vapor profile. The 11-micrometer atmospheric window data yielded surface and/or cloudtop temperatures. For a complete description of the SIRS experiment, see Section 5 of "The Nimbus IV User's Guide" (TRF B06861), available from NSSDC. The SIRS experiment performed normally for several months after launch but began to deteriorate in early 1971. Problems in the SIRS instrument calibration after April 1971, in addition to spacecraft yaw problems, significantly reduced the number of useful soundings obtained. The archival data were produced through April 8, 1971. The experiment operated on a limited time basis until March 6, 1973, when it was placed operationally off. Both NSSDC and SDSD have data. 1.Satellite Infrared Spectrometer Radiance Tapes NSSDC ID 70-025A-04A Media Information: 3 Restored Tapes Time Span: 1970-04-08 to 1971-04-08 (as determined by NSSDC) Description: This set of radiance data is contained on binary magnetic tapes that were created on a CDC 6600 computer. An identical set of tapes generated on an IBM 7094 is also available. The data set contains radiances that were measured at 11-36 micrometer wavelengths. Unusable, erroneous, and improperly sequenced values are not included. It also does not contain the derived temperature profiles, which are available from the National Climatic Data Center, Asheville, North Carolina. For further description of the tape format, see section 1.5.3, vol 1, "The Nimbus 4 Data Catalog," TRF B06582. EXPERIMENT: Image Dissector Camera System (IDCS) PI: Branchflower DESCRIPTION: The Nimbus 4 IDCS experiment was designed to take daytime cloudcover pictures. The pictures could be transmitted to APT (automatic picture transmission) stations using the real-time transmission system (RTTS) or stored on magnetic tape for subsequent playback to ground acquisition stations. This experiment was similar to those flown on Nimbus 3 and ATS 3. The camera was mounted on the bottom of the sensory ring of the satellite and pointed vertically down toward the earth at all times. The image dissector was a shutterless electronic scan and step tube mounted behind a wide-angle (108 deg), 5.7-mm focal length lens. Scanning and stepping functions occurred continuously while the satellite progressed along its orbital path. The field of view of the optics was 73.6 deg along track, and 98.2 deg across track. The image was focused by the camera optics on a photosensitive surface of the image dissector tube. A line-scanning beam scanned the photosensitive surface at 4 Hz with a frame period of 200 s. At the nominal spacecraft altitude (approximately 1100 km), each resulting picture was approximately 1400 km on a side with a ground resolution of 3 km at nadir. The experiment was a success. However, owing to spacecraft yaw problems, archival data were produced only through April 8, 1971. Six days later the spacecraft turned around and flew backwards in orbit, with the resultant loss of all usable data. On May 12, 1971, the spacecraft was successfully rotated 180 deg, and limited data were obtained until February 5, 1972. Data from this experiment are available through the SDSD. For a complete description, see Section 2 in "The Nimbus IV User's Guide" (TRF B06861), available from NSSDC. 1.Nimbus 4 Data Catalogs, on Microfiche NSSDC ID 70-025A-06A Media Information: 48 4x6 in. Black&White Microfiche Time Span: 1970-04-18 to 1971-04-08 (as determined by NSSDC) Description: This catalog contains daily black and white pictorial montages that are made up of adjacent swaths of data from successive orbits. The satellite orbit number is printed below each swath. A transparent grid overlay provides geographic reference. These montages may assist a user in identifying specific data and may be directly useful for some research. The catalog consists of eight volumes, seven of which contain montages. It does not, however, contain background information on the spacecraft or experiment, nor is there a description of the techniques used in processing the data. The "Nimbus IV User's Guide" should be used with this catalog when ordering data.