SIRSN4L1: Nimbus-4 Satellite Infrared Radiance Data

SIRSN4L1 is the Nimbus-4 Satellite Infrared Spectrometer Level 1 Radiance Data product, managed by NASA's GES DISC. It contains 13-channel infrared radiance measurements from 11 to 36 micrometers, used to derive vertical temperature and water vapor profiles of the atmosphere. The data were recovered from original 6250 tapes and are stored as daily files in a proprietary binary format.

Use Cases

• Reconstructing historical atmospheric temperature profiles based on radiance measurements in carbon dioxide bands.
• Analyzing historical water vapor distribution using radiance data from water vapor spectral intervals.
• Studying early satellite instrument performance and calibration for the Nimbus-4 SIRS.
• Conducting climate trend analysis for the 1970-1971 period using near-global infrared observations.

Strengths

• Provides a full year of continuous, near-global coverage from April 1970 to April 1971.
• Contains specific spectral data across 13 infrared channels targeting carbon dioxide and water vapor bands.
• Data was preserved and recovered from original archival tapes, representing a complete mission record.

Limitations

• Data is stored in an original proprietary binary format, which likely requires specialized tools for access and interpretation.
• Column names and detailed data structure are unknown, complicating direct analysis.
• Conflicting 'last updated' metadata (2026 vs. 1971) suggests potential platform synchronization issues.

Provenance

Source

NOAA National Environmental Satellite Data and Information Service; Principal Investigator Dr. David Q. Wark.

Collection Method

Measured by the Nimbus-4 Satellite Infrared Spectrometer (SIRS) instrument using a scan mirror.

Time Range

08 April 1970 to 08 April 1971.

Freshness

The most recent platform update was listed as 2026-04-09, though the data itself is from 1971.

Geography

Near-global coverage from latitude -85 to +85 degrees.