Choose an Observation Period and Replay Time
Select an observation date, start hour in UTC and a duration of 3, 6, 12 or 24 hours. Use play, pause, speed and the timeline to explore the selected interval. During preparation or after an acquisition error, check the displayed status and active period. Previously loaded observations remain available if a request for another period fails.
Open the three-spacecraft comparison to inspect original coordinates, heights, total magnetic field F, observation timestamps and local mean solar time (LT). The enlarged inspection replays their relative positions on a clock independent of the main display.
Distinguish Original Values from Display Interpolation
Positions use original one-second records. Only drawing positions between consecutive valid records are interpolated. Numeric coordinates, F and their timestamps retain the original records; position gaps are not filled. Geocentric latitude, east-positive longitude and WGS84 ellipsoidal height are distinct quantities. The spherical Earth background and ellipsoidal height do not share the same reference surface.
LT is local mean solar time calculated from each spacecraft's original UTC and east-positive longitude, rather than an instrument measurement. Pair differences require records at the same original UTC. LT differences use the shortest signed difference across midnight. Collapsible LT-difference graphs can seek the replay time of their own display.
Inspect Missing Records and Quality Selection
Position validity and scalar F selection are independent. F uses original finite, in-range values with Flags_F 0 or 1. Original missingness, out-of-range values, quality exclusions and missing positions remain distinct. Valid positions can be shown when F is unavailable; F is never reconstructed from another quantity.
Supplementary comparison details show original F, quality flags, geocentric radius, interval counts and selection reasons. This is not a validation of every quality field. Total field includes spatial variation of Earth's main field along the orbit. This display alone cannot establish magnetic disturbances or relationships with earthquakes. It is an academic observation exhibit and provides no forecasts or warnings.
Sources and Illustrative Elements
Observations use Swarm MAG / LR / 1B through ESA / VirES HAPI. After loading, Sources & processing lists each spacecraft's dataset, active interval, retrieval timestamp and original-data SHA-256. See ESA / VirES HAPI and the data terms.
Dots and tracks show observed positions. Enlarged spacecraft models, their attitude and lighting, and callouts with leaders are illustrative and do not depict collision avoidance. Enlarged inspection uses true relative positions. The day/night boundary is a geometric calculation from observation UTC using NOAA/Meeus equations, rather than measured illumination. Twilight and atmosphere colours are illustrative. NASA Blue Marble is a historical composite, without clouds or night imagery from the observation time.
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