NIMBUS 2

About This Satellite

Nimbus 2 launched on May 15, 1966 as a meteorological research spacecraft. Its Medium Resolution Infrared Radiometer supplied observations in five spectral regions, alongside television and high-resolution infrared systems. The mission explored how measured radiation could reveal properties of the atmosphere and surface beyond the patterns visible in an ordinary cloud photograph.

Different channels answer different weather questions

The contemporary report describes information related to water vapour, surface and cloud-top temperatures, outgoing radiation, and reflectivity. These quantities are not interchangeable. A bright feature in a reflected-light product and a bright feature in an infrared display need not have the same physical meaning, even when they occupy the same location.

Research hardware could also support a practical observing gap

The 1966 report notes that Nimbus 2 high-resolution infrared products were used during the interval between a camera failure on ESSA 2 and the launch of ESSA 3. That is a specific example of research observations assisting an operational need. It does not make every Nimbus dataset identical to an ESSA camera product.

Mission reference: NASA: 1966 report on Nimbus 2 meteorological observations. Editorial review: 2026-09-14.

The 1966 observations gained another use decades later

NASA Earthdata describes recovery of Nimbus 1, 2, and 3 observations after decades in storage to extend the context of polar sea-ice measurements back into the 1960s. Nimbus 2 contributed a historical observing year that predates the familiar continuous passive-microwave record beginning in 1979. Recovering an old observation can add information without launching another satellite.

Reference: NASA Earthdata: Nimbus data recovery and early sea-ice observations.

A recovered record is not an uninterrupted climate time series

The restoration account discusses gaps and uncertainty in identifying some sea-ice features. The recovered imagery adds earlier snapshots, not automatically continuous daily coverage between the 1960s and modern instruments. Compare observation dates, sensor characteristics, and interpretation methods before combining the records or describing a historical ice extent as directly equivalent to a modern product.

Reference: NASA Earthdata: interpreting recovered Nimbus sea-ice evidence.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 1,091 km at perigee to 1,175 km at apogee, a difference of 84 km. The orbital period is about 108.0 minutes. Eccentricity 0.00558 indicates a nearly circular path. In a two-body approximation, perigee speed is 1.01 times apogee speed. These are mean-element estimates, not instantaneous measurements. Distance per orbit uses an ellipse approximation.

Saved build snapshot. If a valid TLE is retrieved, this explanation and the orbit panel update together. Otherwise this dated snapshot is retained.

Ground track is not sensor coverage

An inclination of 100.52 degrees implies approximate geocentric ground-track limits of 79.5 degrees north and south. This is a retrograde orbit, moving against the direction of Earth rotation. The plotted line marks the point beneath the object. It does not represent camera coverage, radio reception, or a guaranteed visible pass.

Accuracy and missing information

The introductory record describes the build snapshot. The orbital snapshot explanation and orbit panel share any successfully retrieved TLE; check the displayed epoch. Reentered objects retain historical data only. Mission history is not rewritten by TLE updates. TLE/SGP4 positions are predictions and can change after maneuvers or updated observations. The 14-day stale-data cutoff is a display safeguard, not an accuracy guarantee. Local passes are geometric predictions, not a visibility forecast. No verified operator or mission status means unknown, not active. Do not use this catalog for collision avoidance or operational flight decisions.

Catalog sources: CelesTrak SATCAT: NORAD 2173 · GCAT: S02173 (source update 2026 Sep 4 2345:57). Supplementary metadata: SatNOGS DB, retrieved 2026-09-05T12:57:25.375Z. Page assembled 2026-09-15. GCAT phase codes describe trajectory phases, not mission health.

Learn more: TLE data · Perigee and apogee · Ground tracks · JOT (Jewawud Live Orbital Map)

Satellite Details