ESSA 3 (TOS-A)

About This Satellite

ESSA-3 launched on October 2, 1966 with two Advanced Vidicon Camera System units. Its near-polar orbit carried it around Earth in approximately 114.5 minutes. The 1966 US space report describes twelve photographs stored during each daylight pass for later transmission, rather than continuous video from one fixed viewpoint.

The second camera was a reserve, not a second simultaneous service

Each AVCS unit could independently support the planned cloud-surveillance coverage. Keeping one in reserve was intended to extend useful observing life if the first failed. Two installed cameras therefore did not mean twice the routine image rate.

Cloud photography depended on illumination

The daylight-pass description matters when interpreting coverage: a near-polar orbit alone does not establish nighttime imaging capability. A plotted trajectory shows spacecraft movement, not whether a useful illuminated cloud scene was recorded.

Mission reference: US space activities report 1966, page 93: ESSA-3 cameras and stored imagery. Editorial review: 2026-09-15.

Fewer frames could contain more useful detail

The 1966 report compares 144 pictures per day for ESSA-3 coverage with 450 for ESSA-1, while television scan lines per picture increased from 460 to 830. Wider coverage per frame reduced processing work. These are historical picture-format figures, not a modern digital pixel count.

Reference: US space activities report 1966: ESSA-3 image count and scan-line comparison.

Receiving the pictures was only the start of the weather product

The 1967 report traces AVCS pictures from ESSA-3 and ESSA-5 through ground stations in Alaska and Virginia to central processing at Suitland, Maryland, then to meteorological users worldwide. It separately describes immediate APT broadcasts by ESSA-2, -4 and -6. This distinction explains why satellites in the same family could serve different users and require different receiving infrastructure. Their cloud photographs also lacked nighttime coverage; orbit access and illumination were separate limits.

Reference: US space activities report 1967, pages 78-79: AVCS processing and APT distribution.

Replacement and deactivation are part of the mission history

NASA identifies ESSA-3 as the replacement for ESSA-1 and lists its launch from Vandenberg using a thrust-augmented Delta. It records deactivation on December 2, 1968. That date describes the end of operation, not a reentry event. The surviving catalog identity should therefore be read as a historical spacecraft record, not as an available source of current weather photographs.

Reference: NASA Science: ESSA-3 replacement role, launch site and deactivation date.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 1,386 km at perigee to 1,485 km at apogee, a difference of 99 km. The orbital period is about 114.6 minutes. Eccentricity 0.00635 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 101.06 degrees implies approximate geocentric ground-track limits of 78.9 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 2435 · GCAT: S02435 (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)

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