OBSERVER SKY VIEW
Awaiting observer dataWhere to look
Compass projection of the current sky direction. The chart shows direction, not brightness or a photograph of the sky.
NASA/JPL HORIZONS EPHEMERIS
Where Is Lucy Spacecraft Now? Live Position
NASA · Jupiter Trojan asteroids · Launched 2021-10-16
An asteroid tour
Lucy is a multi-target mission. Its Dinkinesh and Donaldjohanson encounters precede the Jupiter Trojan tour. The Trojans share Jupiter’s orbit around the Sun; they are not moons orbiting Jupiter.
FROM EARTH NOWWaiting for dataSample timestamp will appear here
FROM SUN NOWWaiting for dataSample timestamp will appear here
ONE-WAY RADIO DELAY—Geometric light time to Earth
TIME SINCE LAUNCH—Launch date: 2021-10-16 · calendar-day estimate
Loading current samples independently of the map date.
Radio signal simulator
Estimate a signal’s travel time from a fixed distance sample. No signal is transmitted. Spacecraft motion, processing time and station scheduling are excluded.
An ideal immediate reply takes twice the one-way light time.
Explore mission dates
Snapshots use 12:00 UTC on the selected day, not exact encounter time. Check the map timestamp and data availability. The current summary above stays independent.
Drag to rotate · Scroll/pinch to zoom · Tap a planet to focus
Solar System ViewPlanet sizes are enlarged for visibility; orbital positions use JPL ephemerides.
Loading mission ephemeris…UTC --:--:--
Lucy · FROM YOUR LOCATION
Find the spacecraft in the sky
See where the spacecraft appears in the sky for the location selected above. The chart shows direction and does not guarantee naked-eye or telescope visibility.
Waiting for your selected location…
Right ascension · ICRF—
Declination · ICRF—
Sky direction—
Above horizon—
Rise, highest point and set
Rise above horizon—
Highest altitude—
Set below horizon—
Rise, highest point and set are estimates. Atmospheric refraction and terrain are excluded.
A calculated direction does not imply optical visibility.
Distance from your location
Observer range in astronomical units. Close flybys and maneuvers can change the distance quickly.
About Lucy
A multi-target mission to primitive asteroids, including Jupiter’s Trojan populations.
DestinationJupiter Trojan asteroids
Launched2021-10-16
AgencyNASA
DAILY SKY POSITION
12:00 UTC sample · dates and times labeled UTCThe next 15 days
| Date (UTC) | RA (°) | Dec (°) | Azimuth (°) | Altitude (°) | Range (AU) |
|---|---|---|---|---|---|
| Select your observing location above to load the position table. | |||||
These are observer-based line-of-sight calculations, independent of the compressed scale used in the 3D voyage map. No brightness prediction is made.
TRACKER GUIDE & MISSION EXPLAINER
Lucy Spacecraft Tracker: Journey to the Jupiter Trojan Asteroids
Lucy is NASA's first mission to the Jupiter Trojan asteroids, primitive objects that share Jupiter's orbit around the Sun in two broad swarms. The tracker above uses JPL Horizons ephemerides to follow Lucy's complex solar orbit and changing distance from Earth and Sun.
The spacecraft launched on October 16, 2021. Its long trajectory uses Earth gravity assists and multiple flybys to reach a record number of asteroid targets rather than travelling to one final planet.
Why Trojan asteroids are important
Trojan asteroids occupy regions around the Sun-Jupiter L4 and L5 Lagrange points, leading and trailing Jupiter in its orbit. Their diversity may preserve clues about how the giant planets moved and mixed material during the early Solar System.
Lucy's planned encounters include main-belt asteroids and multiple Trojans. It flew past the main-belt asteroid Donaldjohanson in April 2025 while preparing for the Trojan phase beginning in 2027.
Understanding the tracker path
Horizons supplies a trajectory vector at defined times. The page interpolates cached points to create readable continuous values. Lucy's looping route can look surprising because gravity assists return the spacecraft near Earth and reshape its heliocentric orbit.
The scene cannot show asteroid encounter distances or target sizes at scale. A target may be millions of times smaller than the orbital path represented on screen.
Educational uses
- Follow how an Earth flyby changes heliocentric speed and direction.
- Compare L4 and L5 Trojan populations with the main asteroid belt.
- Examine why a multi-target flyby mission needs precise timing.
- Calculate how light time affects commanding during distant encounters.
- Use official NASA pages to match tracker position with mission milestones.
Limits
The page does not show camera pointing, flyby sequences or instrument status. NASA's mission team provides official encounter information. The displayed distances and vectors are ephemeris-derived and the scene is compressed.
Why the itinerary takes many years
Lucy's targets are spread across different regions of the Solar System and cannot be visited on a simple outward cruise. The spacecraft repeatedly uses orbital geometry to meet objects that are themselves moving rapidly around the Sun. Each encounter must occur at the correct place and time, much like meeting several moving trains without stopping at every station. This makes the mission a useful example of trajectory design, long-term navigation and the scientific value of visiting a diverse sample instead of one representative asteroid.
MISSION REFERENCE · RESEARCH & TRAJECTORY
Lucy science, Trojan encounters and the logic of its long route
Why the Trojan swarms are a science target
Jupiter Trojan asteroids share Jupiter’s orbital path around the Sun, gathering in broad populations ahead of and behind the planet. They are scientifically interesting because their diverse compositions may preserve clues about early Solar System conditions and planetary migration. They are not little moons orbiting Jupiter itself. Lucy’s route brings a spacecraft close enough to examine selected bodies instead of relying only on distant telescopic points of light.
Encounters along a complicated itinerary
Lucy uses Earth gravity assists to reach different targets over a long itinerary. NASA’s current mission material includes encounters with main-belt asteroids on the way to the Trojan populations. At each flyby, the spacecraft has limited time to obtain close-range observations; the long arcs between targets are still an essential part of the mission. A marker moving near Jupiter’s orbit does not mean it has entered orbit around Jupiter. Read the encounter chronology from NASA separately from the current trajectory sample.
What a close pass can measure
Imagery can reveal shape, craters, colour variations and possible satellites; other observations help constrain composition and physical properties. Radio tracking can also contribute information about a target’s mass. Together the measurements help compare objects from different Trojan groups. The tracker on this page displays spacecraft geometry, not raw asteroid imagery or a scientific inference about one target’s origin. Mission data can take time to return, calibrate and interpret after a flyby.
How to use the Earth and Sun distances
Sun distance helps show where Lucy is on its broad interplanetary path, whereas Earth distance reflects both Lucy’s movement and Earth’s changing position. A flyby of Earth can create a sharp dip in the Earth-distance curve without implying a return to launch. The compressed 3D visualization makes the route easier to see but is not a ruler. A calculated observing direction is useful for geometry study; it does not turn the spacecraft into a visible night-sky object.
Frequently asked questions
Why is the mission named Lucy?
It is named after the famous fossil that transformed understanding of human evolution, reflecting hopes that Trojan asteroids will transform knowledge of planetary origins.
Are Trojan asteroids moons of Jupiter?
No. They orbit the Sun near stable regions associated with Jupiter's orbit.
Will Lucy orbit an asteroid?
The mission is designed around a series of flybys rather than entering orbit around each target.
Why does the route return near Earth?
Earth gravity assists alter Lucy's solar orbit and provide energy for later encounters.
Sources and further reading
Educational-use note: SpaceTracker.live is an independent educational website and is not an official mission-control service. Positions, paths, distances and pass predictions are computed from third-party orbital elements or ephemerides. They may be delayed or approximate and must not be used for navigation, collision avoidance or safety-critical decisions.