VANGUARD 2
Country: United States of America
Live Position
Ground Track · Last 90 Minutes
Upcoming Passes · Over Your Location
About This Satellite
Vanguard 2 reached orbit on February 17, 1959, with an experiment intended to measure cloud cover using photocells. It was an early attempt to turn observations from above the atmosphere into useful meteorological information. Successful orbital insertion, however, did not mean that its cloud experiment delivered an interpretable weather record.
The missing ingredient was stable pointing
NASA attributes the problem to a wobble introduced when the third stage bumped the satellite. The returned cloud-cover data could not be interpreted as intended. A light measurement needs a reliable viewing direction: without it, a changing signal cannot confidently be assigned to a particular cloud field.
Cloud detection is not automatically a cloud map
Think of a scanning sensor as collecting samples that must be placed on Earth. Spacecraft position supplies only part of that placement; orientation and timing matter too. Vanguard 2 illustrates why a catalog orbit alone is insufficient to reconstruct an instrument footprint or recover a failed imaging experiment.
Mission reference: NASA Historical Data Book: Vanguard 2 experiment and results. Editorial review: .
A mission with separate launch and science outcomes
The historical summary records the end of transmissions in March 1959. Its two outcomes should remain separate: the launcher placed the payload in orbit, while spacecraft motion compromised the meteorological result. Calling the entire flight either a complete failure or a successful weather service would hide that distinction.
Reference: NASA: Vanguard 2 mission outcome.
Daylight was part of the experiment design
The NASA experiment catalog identifies the target as cloud distribution on the daylight part of the orbit. The instrument depended on reflected light, so this was not an all-hours thermal weather imager. When comparing it with later meteorological satellites, distinguish the illumination requirement from the ability to remain in orbit through the night.
Reference: NASA: Vanguard 2 daylight cloud-cover experiment.
Reading this orbital snapshot
Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 552 km at perigee to 2,894 km at apogee, a difference of 2,341 km. The orbital period is about 120.9 minutes. Eccentricity 0.14452 shows why a single altitude cannot describe the whole path. In a two-body approximation, perigee speed is 1.34 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 32.86 degrees implies approximate geocentric ground-track limits of 32.9 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 11 · GCAT: S00011 (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)