OSCAR 3

About This Satellite

OSCAR 3, also written OSCAR III, demonstrated an amateur-radio repeater in space. AMSAT's history identifies it as the first amateur satellite with a transponder, allowing ground stations to communicate through the spacecraft rather than merely listen to its beacon. Its importance was the communications experiment, not a large or long-lived payload.

The transponder relayed a band of signals

The payload received a band about 50 kHz wide near 146 MHz and retransmitted near 144 MHz with a one-watt transmitter. Its bandwidth allowed more than one station to use the relay at a time. The quoted watt is transmitter power, not a guarantee of received strength or of a usable link from every location.

Eighteen days established a lasting demonstration

AMSAT reports that roughly one thousand amateurs in twenty-two countries used the transponder during its eighteen-day operation. That short experiment demonstrated simultaneous access by multiple stations. Its surviving catalog entry is a historical identifier, not evidence that a radio contact can still be made through the original transponder.

Mission reference: AMSAT history: OSCAR III transponder and multiple-access demonstration. Editorial review: 2026-09-14.

Project OSCAR and AMSAT are not the same historical attribution

AMSAT's official numbering list assigns OSCAR III to Project OSCAR and gives March 9, 1965 as its launch date. AMSAT now administers OSCAR numbering at the original organization's request. The name expands to Orbiting Satellite Carrying Amateur Radio: it identifies participation in that naming tradition, not a single manufacturer shared by all numbered spacecraft. Preserve Project OSCAR as this mission's responsible organization when following its history.

Reference: AMSAT: OSCAR III launch date, responsible organization and naming convention.

The beacon and the transponder had different operating spans

AMSAT's historical presentation describes a battery-powered transponder and beacons powered by batteries and solar panels. It reports beacon operation for several months, beyond the eighteen-day transponder experiment. A beacon sends its own signal; receiving it does not establish that a two-way relay is available. These separate lifetimes should not be collapsed into a single exact shutdown date for every electrical function aboard OSCAR 3.

Reference: AMSAT historical presentation: OSCAR III beacon and transponder power and lifetimes.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 853 km at perigee to 876 km at apogee, a difference of 23 km. The orbital period is about 102.2 minutes. Eccentricity 0.00160 indicates a nearly circular path. In a two-body approximation, perigee speed is 1.00 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 70.07 degrees implies approximate geocentric ground-track limits of 70.1 degrees north and south. This is a prograde orbit, moving in the same general direction as 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 1293 · GCAT: S01293 (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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