| Explorer S-45 | |
| Names List: | Explorer S-45 NASA S-45 |
| Mission Type: | Ionospheric research |
| Operator: | NASA |
| Cospar Id: | EXS-451 |
| Mission Duration: | Failed to orbit |
| Spacecraft: | Explorer S-45 |
| Spacecraft Type: | Science Explorer |
| Spacecraft Bus: | S-45 |
| Manufacturer: | Goddard Space Flight Center |
| Power: | Solar cells and batteries |
| Launch Date: | 25 February 1961, 00:13:16 GMT |
| Launch Rocket: | Juno II (AM-19F) |
| Launch Site: | Cape Canaveral, LC-26B |
| Launch Contractor: | Army Ballistic Missile Agency |
| Destroyed: | Failed to orbit |
| Orbit Reference: | Geocentric orbit (planned) |
| Orbit Regime: | Highly elliptical orbit |
| Orbit Inclination: | 33.0° |
| Orbit Period: | 5013.90 minutes |
| Apsis: | gee |
| Instruments: | Beacon |
| Programme: | Explorer program |
| Previous Mission: | Explorer 9 |
| Next Mission: | Explorer 10 |
Explorer S-45 was a NASA satellite, which was lost in a launch failure in February 1961. The satellite was intended to operate in a highly elliptical orbit, from which it was to have provided data on the shape of the ionosphere,[1] and on the Earth's magnetic field.[2] It was part of the Explorer program, and would have been designated Explorer 10 had it reached orbit. A second identical satellite, Explorer S-45A, also failed to achieve orbit when it was launched.[2]
Explorer S-45 was launched aboard a Juno II launch vehicle, serial number AM-19F. The launch took place from Launch Complex 26B at the Cape Canaveral Air Force Station (CCAFS) at 00:13:16 GMT on 25 February 1961.[3] The launch vehicle malfunctioned after the second stage separated, and contact with the payload was lost.[4] The third stages subsequently failed to ignite, resulting in the satellite failing to achieve orbit.[5]