HRIRN1L1 is the High Resolution Infrared Radiometer (HRIR) Nimbus-1 Level 1 Meteorological Radiance Data (NMRT) product and contains infrared radiances converted to equivalent black-body temperature or "brightness" temperature values. he data, originally written on IBM 360 machines, were recovered from magnetic tapes, also referred to as Nimbus Meteorological Radiation Tapes (NMRT). The data are archived in their original IBM 36-bit word proprietary format, also referred to as a binary TAP file.

The HRIR instrument 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 HRIR instrument was launched on the Nimbus-1 satellite and was operational from August 28, 1964 through September 22, 1964 when the spacecraft malfunctioned. Dr. L. L. Foshee of the US Army Electronics Command was the Principal Investigator.

Measurements taken during daytime do not reveal true surface temperaturessince the radiometer operates in the 3.5 to 4.1 micron region, and reflectedsolar radiation is added to emitted surface radiation. However, reflected sunlight in this spectral region does not saturate the radiometer output and usable pictures can be made.

This product was previously available from the NSSDC with the identifier ESAD-00209 (old ID 64-052A-03A).