Transit 4 Satellite Bus
Data current as of 2026-07-20.
The Transit 4 bus accounts for 3 cataloged objects, of which 3 are in orbit and 0 are active. Most are built by Applied Physics Laboratory (APL). The largest operator on this bus is Bureau of Naval Weapons (BUWEPS). All were launched in 1961.
3
In orbit
0
Active
3
Total launched
0
Reentered
Transit 4 launched per year
Still in orbit Click a year to list its satellites.
Typical specifications
Most common values across cataloged Transit 4 satellites.
| Manufacturer | Applied Physics Laboratory (APL) |
|---|---|
| Purpose | Navigation |
| Launch mass | 109 kg |
| Dry mass | 109 kg |
| Length | 0.8 m |
| Diameter | 1.1 m |
| Span | 1.1 m |
| Shape | Cylindrical |
| Power | Primary power from solar cells; secondary power from the SNAP-3 RTG. |
| Propulsion | N/A |
| Design life | Operated for approximately 15 months, providing navigation data until its mission concluded. |
| Equipment | Particle detectors, solar attitude detectors, magnetometers, Doppler system |
| Typical orbit | 106 min period, 32° inclination |
Top operators
Bureau of Naval Weapons (BUWEPS) 2 U.S. Navy 1
Top countries
US 3
Transit 4 satellites
Track any of them live in KeepTrack.
| Name | NORAD | COSPAR | Owner | Launched | Orbit | Status | Track |
|---|---|---|---|---|---|---|---|
| TRAAC Transit Research and Attitude Control | 00205 | 1961-031B | Bureau of Naval Weapons (BUWEPS) | Nov 15, 1961 | 106 min, 32.4° | Inactive | ◉ |
| TRANSIT 4B Transit IV-B | 00202 | 1961-031A | U.S. Navy | Nov 15, 1961 | 106 min, 32.4° | Inactive | ◉ |
| TRANSIT 4A Transit IV-A | 00116 | 1961-015A | Bureau of Naval Weapons (BUWEPS) | Jun 29, 1961 | 103 min, 66.8° | Inactive | ◉ |
Frequently asked questions
How many Transit 4 satellites are there?
The catalog lists 3 objects built on the Transit 4 bus. 3 are in orbit and 0 have reentered.
How many Transit 4 satellites are in orbit?
3 Transit 4 objects are currently in orbit, of which 0 carry an active status.
Who builds the Transit 4 bus?
The Transit 4 bus is most commonly built by Applied Physics Laboratory (APL).
When did the first Transit 4 satellite launch?
The cataloged Transit 4 satellites all launched in 1961.