The Nimbus I satellite was launched on August 28, 1964 on a Thrust Augmented Thor (TAT)/ Agena B vehicle. Nimbus I was planned to be placed in a circular sun-synchronous orbit, but a short second-stage burn resulted in an unplanned eccentric orbit. Otherwise, the spacecraft and its experiments operated successfully until September 22, 1964 when the solar paddles became locked in position, resulting in inadequate electrical power to continue operations.
The elliptical orbit had an apogee of 937 km and a perigee height of 429 km with an inclination of 98.66 degrees and a nodal period of 98.42 minutes.
Three instruments were on board of the spacecraft.
An Advanced Vidicon Camera System (AVCS) provided clouds in the earth atmosphere and, in clear areas, terrestrial features on the earth's surface (only during day-time).
An Automatic Picture Transmission (APT) system was a camera and transmitter combination designed to transmit local daytime, slow-scan television pictures of cloud cover conditions.
A High Resolution Infrared Radiometer (HRIR) was available to provide earth cloud cover (nighttime) and to measure the temperatures of cloud tops and terrain features.
The Nimbus I HRIR instrument was operational from August 28, 1964 through September 22, 1964. The Nimbus I High Resolution Infrared Radiometer (HRIR) was designed to perform two major functions: First, to map the Earth's cloud cover at night to complement the television coverage during the daytime portion of the orbit, and second, to measure the temperature of cloud tops and terrain features.
The single scanning radiometer uses a PbSe photoconductive detector cell and provides measurements of blackbody temperatures 210K – 330K. The radiometer operates in the 3.5 to 4.1 micron window. The scan mirror is inclined to 45 degrees with a scan rate of 44.7 revolutions per minute. The Instantaneous field of view is 8.8 milliradians and the scan line separation is 8.3 km. The ground resolution is approximately 8 km at nadir.
More information can be found in the Nimbus I HRIR Readme file or the Nimbus I Users' Guide.
You may download the Nimbus I HRIR data products by selecting the "Data Holding" link on the menu bar. If you have questions on GES DISC data product support and services for the Nimbus I HRIR and related data sets, please let us know.