ISIS 1
Country: Canada · Also known as: International Satellite for Ionospheric Studies
Live Position
Ground Track · Last 90 Minutes
Upcoming Passes · Over Your Location
About This Satellite
ISIS 1 launched on January 30, 1969 as part of the joint Canadian-US International Satellites for Ionospheric Studies programme. It investigated the charged upper atmosphere and processes associated with the aurora. Understanding that environment mattered to long-distance radio communication, whose propagation could be disrupted by changing ionospheric conditions.
A recorder separated observing time from contact time
ISIS 1 combined fixed- and swept-frequency sounders with direct-measurement experiments and a tape recorder. Its onboard timing system could activate experiments and recording outside ground-station view. This allowed observations to be collected between contacts; the times when a receiving station saw the spacecraft were not the complete observing schedule.
Do not give ISIS 1 the later satellite's optical milestone
The Canadian Space Agency attributes the added optical sensors and whole-auroral-oval imaging milestone to ISIS 2. ISIS 1's ionospheric measurements should not be illustrated or described as though it carried that later optical payload. Similar programme names are not evidence of identical instruments.
Mission reference: Canadian Space Agency: ISIS 1 instruments and mission history. Editorial review: .
Apparent range is not automatically true altitude
NASA's restoration documentation distinguishes ionograms with different apparent-range sampling from electron-density profiles obtained through processing. Radio propagation through plasma makes interpretation more involved than reading a height directly from a plotted echo. Before comparing a trace with an orbital altitude, check which coordinate and processing stage the archive product actually represents.
Reference: NASA SPDF: ionogram formats and true-height processing.
A long mission did not leave a complete digital archive
The restoration project describes converting original analog telemetry into digital ionograms and notes that not all historical observations were processed. It also documents deterioration and destruction of many later tapes. An empty search result can therefore reflect preservation or selection limits, not proof that the spacecraft made no observation. Use the archive coverage notes before drawing conclusions from missing data.
Reference: NASA SPDF: data preservation and gaps in the Alouette/ISIS archive.
Reading this orbital snapshot
Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 576 km at perigee to 3,440 km at apogee, a difference of 2,864 km. The orbital period is about 127.4 minutes. Eccentricity 0.17078 shows why a single altitude cannot describe the whole path. In a two-body approximation, perigee speed is 1.41 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 88.44 degrees implies approximate geocentric ground-track limits of 88.4 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 3669 · GCAT: S03669 (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)