IMP Satellite Bus
Data current as of 2026-07-20.
The IMP bus accounts for 10 cataloged objects, of which 3 are in orbit and 0 are active. 7 have reentered. Most are built by GSFC. The largest operator on this bus is NASA. The first launched in 1963, the most recent in 1978.
3
In orbit
0
Active
10
Total launched
7
Reentered
IMP launched per year
Still in orbit Since reentered Click a year to list its satellites.
Typical specifications
Most common values across cataloged IMP satellites.
| Manufacturer | GSFC |
|---|---|
| Purpose | Research, Magnetosphere |
| Launch mass | 266 kg |
| Dry mass | 266 kg |
| Length | 0.3 m |
| Diameter | 0.7 m |
| Span | 2.5 m |
| Shape | Oct Cyl + 4 Pan + 2 Ant |
| Power | Solar cells, batteries |
| Propulsion | Star 17A |
| Typical orbit | 17381 min period, 9° inclination |
Top operators
Top countries
US 10
IMP satellites
Track any of them live in KeepTrack.
| Name | NORAD | COSPAR | Owner | Launched | Orbit | Status | Track |
|---|---|---|---|---|---|---|---|
| ISEE-3 (ICE) ISEE 3 | 11004 | · | GSFC | Aug 12, 1978 | · | Inactive | ◉ |
| ISEE-1 ISEE 1 | 10422 | 1977-102A | GSFC | Oct 22, 1977 | 3439 min, 8.7° | Reentered | ◉ |
| EXPLORER 50 (IMP-8) IMP 8 | 06893 | 1973-078A | GSFC | Oct 26, 1973 | 17381 min, 9.1° | Inactive | ◉ |
| EXPLORER 47 (IMP-7) IMP 7 | 06197 | 1972-073A | GSFC | Sep 23, 1972 | 18273 min, 48.4° | Inactive | ◉ |
| EXPLORER 43 (IMP-6) IMP 6 | 05043 | 1971-019A | GSFC | Mar 13, 1971 | 5966 min, 31.4° | Reentered | ◉ |
| EXPLORER 41 (IMP-5) IMP 5 | 03990 | 1969-053A | GSFC | Jun 21, 1969 | 4841 min, 84.5° | Reentered | ◉ |
| EXPLORER 34 (IMP-4) IMP 4 | 02817 | 1967-051A | GSFC | May 24, 1967 | 6216 min, 71.6° | Reentered | ◉ |
| EXPLORER 28 (IMP-3) IMP 3 | 01388 | 1965-042A | GSFC | May 29, 1965 | 8342 min, 53.6° | Reentered | ◉ |
| EXPLORER 21 (IMP-2) IMP 2 | 00889 | 1964-060A | GSFC | Oct 4, 1964 | 2080 min, 33.7° | Reentered | ◉ |
| EXPLORER 18 (IMP-1) IMP 1 | 00693 | 1963-046A | GSFC | Nov 27, 1963 | 5611 min, 35.2° | Reentered | ◉ |
Frequently asked questions
How many IMP satellites are there?
The catalog lists 10 objects built on the IMP bus. 3 are in orbit and 7 have reentered.
How many IMP satellites are in orbit?
3 IMP objects are currently in orbit, of which 0 carry an active status.
Who builds the IMP bus?
The IMP bus is most commonly built by GSFC.
When did the first IMP satellite launch?
The first cataloged IMP satellite launched in 1963, and the most recent in 1978.