ESSA 1 (OT-3)

About This Satellite

ESSA-1 launched on February 3, 1966 to supply cloud photographs for operational weather analysis and forecasting at the US National Meteorological Center. It carried two cameras on opposite sides of its body. Its contribution was a repeatable view of weather systems from orbit, rather than a continuous movie of the whole planet.

The spacecraft rolled so its cameras could face Earth

ESSA-1 used the cartwheel arrangement demonstrated by TIROS-9. Magnetic attitude control oriented the spin axis perpendicular to the orbital plane, allowing a side-mounted camera to face Earth during each rotation. The spacecraft spin and its revolution around Earth were separate motions that had to work together for useful photography.

Repeated local-time observations supported weather comparisons

NASA describes a near-polar, retrograde Sun-synchronous orbit with an inclination near 98 degrees. This provided repeated observations under similar local-time conditions. The ground track identifies where the spacecraft passed, while the camera orientation and timing determined which cloud scenes were actually recorded.

Mission reference: NASA Science: ESSA-1 cloud photography and cartwheel orientation. Editorial review: 2026-09-15.

From onboard tape to a weather map in Maryland

The 1966 presidential space report describes ESSA-1 storing pictures on tape for later transmission to command and data-acquisition stations near Fairbanks and at Wallops. High-speed links forwarded the signals to Suitland, Maryland, where pictures were reconstructed and geographic grids and coastlines added electronically. This was a store-and-forward workflow. The report separately assigns direct local Automatic Picture Transmission to ESSA-2; the two satellites should not be given identical downlink descriptions.

Reference: 1966 US space activities report, pages 92-93: ESSA-1 recording and ground processing.

One camera failure exposed the limits of global coverage

The same contemporary report records a camera failure on July 25, 1966 and an approximately forty-percent reduction in ESSA-1 global coverage capability. Observations from ESSA-2, TIROS-9 and Nimbus-2 helped compensate until ESSA-3 launched, but the combined coverage was still incomplete and analysis took longer. A spacecraft remaining in orbit therefore did not mean its original observing service continued unchanged.

Reference: 1966 US space activities report: camera failure and the combined replacement observations.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 675 km at perigee to 787 km at apogee, a difference of 112 km. The orbital period is about 99.4 minutes. Eccentricity 0.00789 indicates a nearly circular path. In a two-body approximation, perigee speed is 1.02 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 97.81 degrees implies approximate geocentric ground-track limits of 82.2 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 1982 · GCAT: S01982 (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