Explorer 18

Explorer 18
	Explorer-18 (IMP-A) satellite
Names	IMP-A; IMP-1; Interplanetary Monitoring Platform-1; S-74
Mission type	Space physics
Operator	NASA
COSPAR ID	1963-046A
SATCAT no.	00693
Spacecraft properties
Spacecraft	IMP
Manufacturer	Goddard Space Flight Center
Launch mass	138 kg (304 lb)
Power	4 deployable solar arrays and batteries
Start of mission
Launch date	27 November 1963,; 02:30:01 GMT
Rocket	Thor-Delta C; (Thor 387 / Delta 021)
Launch site	Cape Canaveral, LC-17B
Contractor	Douglas Aircraft Company
Entered service	27 November 1963
End of mission
Last contact	10 May 1965
Decay date	30 December 1965
Orbital parameters
Reference system	Geocentric orbit
Regime	Highly elliptical orbit
Perigee altitude	4,395 km (2,731 mi)
Apogee altitude	192,003 km (119,305 mi)
Inclination	35.20°
Period	5606 minutes
Instruments
Instruments
	Cosmic-Ray Range versus Energy Loss
	Cosmic Rays
	Faraday Cup
	Fluxgate Magnetometers
	Ion Chamber and Geiger–Müller Counters
	Retarding Potential Analyzer
	Solar Wind Protons
	Explorers program ← Explorer 17 Explorer 19 → Interplanetary Monitoring Platform IMP-B →

Explorer 18, also called IMP-A, IMP-1, Interplanetary Monitoring Platform-1 and S-74, was a NASA satellite launched as part of the Explorer program. Explorer 18 was launched on 27 November 1963 from Cape Canaveral Air Force Station (CCAFS), Florida, with a Thor-Delta C launch vehicle. Explorer 18 was the first satellite of the Interplanetary Monitoring Platform (IMP). Explorer 21 (IMP-B) launched in October 1964 and Explorer 28 (IMP-C) launched in May 1965 also used the same general spacecraft design.^[3]

^ "Launch Log". Jonathan's Space Report. 21 July 2021. Retrieved 31 October 2021.
^ ^a ^b "Trajectory: IMP-A 19643-046A". NASA. 28 October 2021. Retrieved 31 October 2021. This article incorporates text from this source, which is in the public domain.
^ "Explorer-series reference images". Retrieved 4 July 2021.