HELIOS 1B
Helios 1B was a French-led military Earth-observation satellite launched in 1999, part of Europe's early optical reconnaissance capability.
Object identity
- NORAD ID
- 25977
- COSPAR ID
- 1999-064A
- Operator
- Not listed
- Country
- Not listed
- Launch date
- Not listed
Immediate discovery
Why this satellite matters
Optical reconnaissance from orbit depends on the same geometry as civilian imaging: altitude, focal length, aperture, detector sampling and atmospheric conditions all affect what can be resolved.
Understanding the mission
Science and engineering ideas
Optical reconnaissance from orbit depends on the same geometry as civilian imaging: altitude, focal length, aperture, detector sampling and atmospheric conditions all affect what can be resolved.
Mission
Mission and purpose
The current public orbital catalog identifies this object, but verified mission-specific information may be limited. TransitSatellite will expand this page when authoritative information is available.
- Optical reconnaissance from orbit depends on the same geometry as civilian imaging: altitude, focal length, aperture, detector sampling and atmospheric conditions all affect what can be resolved.
Design
Engineering
Optical reconnaissance from orbit depends on the same geometry as civilian imaging: altitude, focal length, aperture, detector sampling and atmospheric conditions all affect what can be resolved.
Real orbital values
The mathematics
The current two-line element set reports approximately 14.882 revolutions per day. Dividing 1,440 minutes by that value gives an estimated orbital period of 96.8 minutes.
Period
96.8 min
Representative speed
27,201 km/h
Representative altitude
611 km
Inclination
98.15°
Launch record
Launch and deployment
Helios 1B launched on 3 December 1999 aboard an Ariane 4 from Kourou.
Orbit
LEO orbit explained
Low Earth orbit is the region closest to Earth used by most crewed spacecraft, many science missions, Earth-observation satellites, and large constellations. Objects move quickly and commonly complete an orbit in roughly 90 to 130 minutes.
LEO can provide detailed Earth views, lower communications delay, and easier access than higher orbits, but it covers less area per spacecraft and is more affected by atmospheric drag.
Live TransitSatellite experience
See HELIOS 1B moving now
Open the live tracker to view its current calculated position, trajectory, orbital information, visibility tools, and Save and Share controls.
Learning
Questions to explore
- What can an orbit tell us before the mission is fully identified?
- Why are stable catalog identifiers important?
Evidence
Sources and data notes
Current identity and orbital elements come from CelesTrak’s public GP data. Calculated orbit values are derived from the current TLE and may change after catalog updates. Mission-history claims are added separately and require authoritative sources.
Catalog updated
Sep 17, 2026, 8:52 AM UTC
Story review
1970-01-01T00:00:00.000Z