| Explorer S-45A | |
| Names List: | S-45A NASA S-45A |
| Mission Type: | Ionosphere research |
| Operator: | NASA |
| Cospar Id: | EXS-451 |
| Mission Duration: | Failed to orbit |
| Spacecraft: | Explorer S-45A |
| Spacecraft Type: | Science Explorer |
| Spacecraft Bus: | S-45 |
| Manufacturer: | Goddard Space Flight Center |
| Power: | Solar cells and batteries |
| Launch Date: | 24 May 1961, 19:48:05 GMT |
| Launch Rocket: | Juno II (AM-19G) |
| 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 11 |
| Next Mission: | Explorer S-55 |
Explorer S-45A was a NASA satellite, which was lost in a launch failure in 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 12 had it reached orbit. It was the second of two identical satellites to be launched; the first, Explorer S-45, had also been lost in a launch failure, earlier in the year.[2]
Explorer S-45A was launched aboard a Juno II launch vehicle, serial number AM-19G. It was the final flight of the Juno II. The launch took place from LC-26B at the Cape Canaveral Air Force Station (CCAFS) at 19:48:05 GMT on 24 May 1961.[3] The system which was intended to ignite the second stage malfunctioned, and as a result that stage failed to ignite.[4] The launch vehicle failed to achieve orbit.[5]