The Nimbus-B meteorological R&D satellite was designed to serve as a stabilized,
earth-oriented platform for the testing of advanced systems for sensing and collecting
meteorological data. The spacecraft consisted of three major structures:
- a sensor mount,
- solar paddles, and
- the control housing unit, which was connected to the sensor mount by a truss structure.
Shaped somewhat like an ocean buoy, Nimbus-B was nearly 3.7 m tall, 1.5 m in diameter
at the base, and about 3 m across with solar paddles extended. The torus-shaped sensor
mount, which formed the satellite base, housed the electronics equipment and battery
modules. The lower surface of the torus provided a mounting space for sensors and
telemetry antennas. An H-frame structure mounted within the center of the torus provided
support for the larger experiments and tape recorders. Mounted on the control housing
unit, which was located on top of the spacecraft, were sun sensors, horizon scanners, gas
nozzles for attitude control, and a command antenna. Use of 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 experiment subsystems on Nimbus-B
consisted of
- a satellite infrared spectrometer (SIRS) for determining the verticle temperature
profiles of the atmosphere,
- an infrared interferometer spectrometer (IRIS) for measuring the emission spectra of the
earth-atmosphere system,
- 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,
- a monitor of ultraviolet solar energy (MUSE) for detecting solar UV radiation,
- 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 (DHRSS),
- a radioisotope thermoelectric generator (RTG), SNAP-19, to assess the operational
capability of radioisotope power for space applications, and
- an interrogation, recording, and location system (IRLS) designed to locate, interrogate, record, and retransmit meteorological data from remote collection stations.
The spacecraft never achieved orbit because of a malfunction in the booster guidance
system forced the destruction of the spacecraft and its payload during launch. No
radioactivity was released in the environment. The SNAP-19 RTG was salvaged from the
water, refurbished and later flown on Nimbus 3.
Less than 1 yr later, an identical payload was successfully flown on Nimbus 3. Nimbus 3
was successful and performed normally until 22 July 1969, when the IRIS experiment
failed. The HRIR and SIRS experiments were terminated on 25 January 1970, and June 21,
1970, respectively. The remaining experiments continued operation until September 25,
1970, when the rear horizon scanner failed. Without this horizon scanner, it was
impossible to maintain proper spacecraft attitude, thus making most experimental
observations useless. All spacecraft operations were terminated on 22 January 1972.
