- NORAD 21527
- 1991-045A
- Low Earth orbit
Current orbit
View on live mapOrbit began over the Indian Ocean
Orbit ends over the Indian Ocean
In the Earth’s shadow since
Back in sunlight
In view from you
Nobody watches REX go over, but a receiver still asks whether it is above the horizon. Say where you are and this card answers.
Your position is rounded to about a kilometre and sent only to the Orbinauts API, to find the pass.
No brightness has been published for REX, so it is not a naked-eye satellite and no city page carries pass times for it. Nothing here estimates one.
Seeing it
There is nothing to go outside for: it is too faint to see with the naked eye from anywhere on Earth.
Timeline
- Launch
Launched, on the day GCAT records. Source
- Close approach
On Wednesday, Oct 28 at 7:15 AM UTC, a fragment of Fengyun 1C (NORAD 47101) was to pass within 826 m of REX (NORAD 21527). The chance was about 1 in 7,000.
Summary
Over Russia LIVE
Where is REX?
At 6:21:43 PM UTC REX was over Russia (70.2° N, 107.8° E), 850 km up, moving at 7.42 km/s and in the Earth’s shadow.
What is REX?
A satellite in low Earth orbit, in space since Jun 29, 1991.
Can I see REX?
No, not with the naked eye: no brightness has been published for REX, and nothing here estimates one.
General
- Operator
- US Air Force Rome Labs, Griffiss AFB
- State
- United States of America
- Built by
- Defense Systems Inc
- Launched
- Mass
- 85 kg
- Operating
- Orbit class
- Low Earth orbit
From GCAT, Jonathan McDowell’s general catalogue, licensed CC BY 4.0: the operator, the state, the manufacturer, the launch day, the mass, and whether it is operating. The orbit class is read from its current elements.
Latest orbital data
- Position received
- 6:21 PM UTC
- Station time (UTC)
- 6:21 PM UTC
- Latitude / longitude
- 70.2° N, 107.8° E
- Altitude
- 850 km
- Speed
- 7.42 km/s (26,716 km/h)
- Course
- south
- Light
- In the Earth’s shadow until 6:52 PM UTC
- Inclination
- 89.5°
- Orbital period
- 101.2 minutes
- Orbits per day
- 14.24
- This orbit
- 762 to 858 km
- In shadow
- 33 minutes of each orbit
- In view from
- Within 2,190 km of the point below it
- Elements epoch
- Nov 8, 2026, 6:02 AM, 12 hours old
- Source
- Position from Space-Track orbital elements of Nov 8, 2026, 6:02 AM, 12 hours old.
No operator publishes an ephemeris for REX, so every position here comes from its orbital elements.
In orbit
- Close approaches
- 1 reported. No close approach to REX is reported for the next three days.
From Space-Track’s public conjunction messages; the latest report was issued Nov 8, 2026, 1:11 PM, 3 hours old. Only approaches serious enough to be reported publicly are listed: within three days and, for two bodies near the Earth, closer than a kilometre with a chance of a collision above 1 in 10,000, the level at which NASA moves the ISS.
Launched with
REX shares its launch, 1991-045, with 5 other bodies the catalogue lists in orbit.
| Body | What it is |
|---|---|
| SCOUT G-1 R/B | Rocket body |
| SCOUT G-1 DEB | Debris |
| SCOUT G-1 DEB | Debris |
| SCOUT G-1 DEB | Debris |
| SCOUT G-1 DEB | Debris |
Read from the international designators of the US catalogue: the year and the launch number every piece of one launch shares. A body that has come down is no longer listed.
Data and API
The current elements from Space-Track as an OMM object, epoch Nov 8, 2026, 6:02 AM, 12 hours old.
{
"OBJECT_NAME": "REX",
"OBJECT_ID": "1991-045A",
"EPOCH": "2026-11-08T06:02:00.929760",
"MEAN_MOTION": 14.23606778,
"ECCENTRICITY": 0.0066513,
"INCLINATION": 89.5364,
"RA_OF_ASC_NODE": 252.4617,
"ARG_OF_PERICENTER": 233.2546,
"MEAN_ANOMALY": 126.2528,
"EPHEMERIS_TYPE": 0,
"CLASSIFICATION_TYPE": "U",
"NORAD_CAT_ID": 21527,
"ELEMENT_SET_NO": 999,
"REV_AT_EPOCH": 83559,
"BSTAR": 0.000043370251,
"MEAN_MOTION_DOT": 0.00000113,
"MEAN_MOTION_DDOT": 0
}