Explorer 4
Names | Explorer IV 1958 Epsilon 1 |
---|---|
Mission type | Earth science |
Operator | JPL / Army Ballistic Missile Agency |
Harvard designation | 1958 Epsilon 1 |
COSPAR ID | 1958-005A |
SATCAT no. | 00009 |
Mission duration | 71 days (achieved) |
Spacecraft properties | |
Spacecraft | Explorer IV |
Spacecraft type | Science Explorer |
Bus | Explorer 1 |
Manufacturer | Jet Propulsion Laboratory |
Launch mass | 25.50 kg (56.2 lb) |
Dimensions | Cylinder: 94.6 cm (37.2 in) long, 16.5 cm (6.5 in) in diameter, Total length with attached rocket motor: 2.05 m (6 ft 9 in) |
Start of mission | |
Launch date | 26 July 1958, 15:00:57 GMT |
Rocket | Juno I (RS-24) |
Launch site | Cape Canaveral, LC-5 |
Contractor | Army Ballistic Missile Agency |
Entered service | 26 July 1958 |
End of mission | |
Last contact | 5 October 1958 |
Decay date | 23 October 1959 |
Orbital parameters | |
Reference system | Geocentric orbit[1] |
Regime | Medium Earth orbit |
Perigee altitude | 263 km (163 mi) |
Apogee altitude | 2,213 km (1,375 mi) |
Inclination | 50.30° |
Period | 110.20 minutes |
Instruments | |
Charged Particle Detector | |
Explorer program |
Explorer 4 was an American satellite launched on 26 July 1958. It was instrumented by Dr.
Explorer 4 was a cylindrically shaped satellite instrumented to make the first detailed measurements of charged particles (protons and electrons) trapped in the terrestrial radiation belts.
Juno I launch vehicle
The launch vehicle was a Juno I, a variant of the three-stage Jupiter-C with an added fourth propulsive stage, which in this case was the Explorer 4. The first stage was an upgraded Redstone liquid-fueled rocket. The second stage comprised a cluster of eleven Sergeant solid-fuel rocket motors and the third stage held three Sergeants. The booster was equipped to spin the fourth stage in increments, leading to a final rate of 750 rpm about its long axis.[2]
Instrument
Charged Particle Detector
The purpose of this experiment was to extend the first measurements of the trapped radiation belt discovered with
Mission
Explorer 4 was launched on 26 July 1958 at 15:00:07 GMT from the Cape Canaveral Missile Test Center of the Atlantic Missile Range. The spacecraft was injected into an initial 263 × 2,213 km (163 × 1,375 mi) orbit with an inclination of 50.30° and a period of 110.20 minutes at 15:07 GMT.[1] This was a much higher inclination and apogee than previous Explorer to allow it to sample more area at higher altitudes. Soon after orbit insertion, the spacecraft developed an end-over-end tumbling motion with a period of about 6 seconds, which affected the measurements and signal level throughout the mission.
The mission remained secret from the public for six months.[4] The satellite telemetry was analyzed for three Operation Argus nuclear weapons tests at high altitude. Explorer 4 was in orbit and operational during the three Project Argus launches 27 August 1958 to 6 September 1958, part of the mission objective was to observe the effects of these high-altitude A-bomb detonations on the space environment.[2]
An unexpected tumble motion of the satellite made the interpretation of the detector data very difficult. The low-power transmitter and the plastic scintillator detector failed on 3 September 1958. The two
See also
- Explorer program
- Operation Argus
References
- ^ a b "Trajectory: Explorer 4 1958-005A". NASA. 28 October 2021. Retrieved 12 November 2021. This article incorporates text from this source, which is in the public domain.
- ^ a b c "Display: Explorer 4 1958-005A". NASA. 28 October 2021. Retrieved 1 November 2021. This article incorporates text from this source, which is in the public domain.
- ^ "Experiment: Charged Particle Detector". NASA. 28 October 2021. Retrieved 1 November 2021. This article incorporates text from this source, which is in the public domain.
- ^ Herlihy, Ed (Narrator). Project Argus — "Greatest Experiment": 3 A-Blasts In Space (video). Universal International News. Event occurs at 29 seconds. Archived from the original on 11 December 2021. Retrieved 9 September 2012.
"To monitor the radiation shell in outer space, the satellite Explorer 4 was launched. And all of this in a secrecy not broken for six months".