NIMBUS 3
Country: United States of America
Live Position
Ground Track · Last 90 Minutes
Upcoming Passes · Over Your Location
About This Satellite
Nimbus 3 launched on April 14, 1969 carrying the Satellite Infrared Spectrometer, SIRS, and the Infrared Interferometer Spectrometer, IRIS. The mission helped turn infrared observations into information about the vertical structure of the atmosphere. That was a different task from simply mapping where clouds appeared across Earth.
A sounding is a profile, not a single surface temperature
The atmospheric-sounding approach uses spectral information to infer temperature structure through the air. NASA's retrospective connects the Nimbus 3 measurements with the effort to supply global atmospheric information to forecasting. Interpreting a spectrum requires a retrieval method; the satellite does not lower a thermometer through successive atmospheric layers.
The ground analysis was part of the scientific result
NASA recounts how William Smith and Harold Woolf processed and hand-plotted the early global data for the National Meteorological Center. The spacecraft measurements became useful through analysis and delivery to forecasters. A raw signal, a retrieved profile, and a forecast are distinct stages rather than three names for the same observation.
Mission reference: NASA: Nimbus 3 and the beginning of satellite atmospheric sounding. Editorial review: .
Two sounders did not have the same operating lifetime
NASA's experiment catalog records IRIS failing on July 22, 1969 and SIRS ending on June 21, 1970. The high-resolution infrared radiometer had already ended on January 25, 1970. A request for Nimbus 3 data therefore needs an instrument name and observing interval, not just the satellite's launch and final shutdown dates.
Reference: NASA experiment catalog: separate Nimbus 3 instrument end dates.
Losing an attitude reference compromised the observations
The same catalog records a rear horizon-scanner failure on September 25, 1970 that prevented proper spacecraft attitude control and made most operational observations unusable. All spacecraft operations ended on January 22, 1972. Surviving in orbit and returning interpretable measurements were separate outcomes: a sensor also needs sufficiently known and controlled viewing geometry.
Reference: NASA experiment catalog: Nimbus 3 attitude failure and shutdown.
Reading this orbital snapshot
Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 1,069 km at perigee to 1,129 km at apogee, a difference of 60 km. The orbital period is about 107.2 minutes. Eccentricity 0.00400 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 99.69 degrees implies approximate geocentric ground-track limits of 80.3 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 3890 · GCAT: S03890 (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)