1. EXPLORER 1

2. EXPLORER 1
REF: – 50th Anniversary of the Space Age.
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Sputnik’s launch in 1957 brought a renewed sense of urgency to the American Space Age efforts. Since 1955, The U.S. had been working on launching a man-made object into Space as part of the NAVY-run Vanguard Project.

3. EXPLORER 1
The official name of the Explorer 1 Mission was: Satellite 1958 Alpha. It was the first Earth satellite of the U.S. and the mission duration was 111 days.
REF: – 50th Anniversary of the Space Age.
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Explorer 1 launch date:

4. EXPLORER 1
The EXPLORER 1 was launched on a Jupiter-C (or JUNO 1), which was a type of sounding rocket used for three sub-orbital spaceflights conducted in 1956 and It was designed by the Army Ballistic Missile Agency (ABMA), and all three flights were launched from the Cape Canaveral Air Force Station, in Florida.
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Juno I satellite launch vehicle. (USAF)

5. EXPLORER 1
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Three key Explorer 1 team members triumphantly display a full-scale model of the satellite after its successful launch. From left to right: William H. Pickering, director of the Jet Propulsion Laboratory, which designed and built Explorer. James A. Van Allen, University of Iowa physicist who directed the design and creation of Explorer’s instruments. Wernher von Braun, head of the U.S. Army Ballistic Missile Agency team that designed and built the Jupiter-C rocket.
Explorer 1 Identical backup for the original satellite
This satellite was built as a backup-an identical unit for the original Explorer 1. It could have been launched if the first one had failed. The striped portion contains the instruments, radios, and batteries. It is attached to a single solid-propellant rocket motor, which served as the launch vehicle's fourth stage.
Length: 203 cm (80 in), including rocket motor Diameter: 15 cm (6 in) Weight: 13.9 kg (30.7 lb) Launch Vehicle: Jupiter-C (Juno I) Transferred from the Jet Propulsion Laboratory and NASA
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EXPLORER 1 carried instrumentation to measure internal and external temperatures, micrometeorite impacts, and an experiment (including a Geiger counter) designed by James A. Van Allen and his team from Iowa State to measure the density of electrons and ions in space.

6. EXPLORER 1
The measurements made by Van Allen's experiment led to an unexpected and startling discovery -- an earth-encircling belt of high energy electrons and ions trapped in the magnetosphere, now known as the Van Allen Belt.
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Cosmic radiation entering the Earth’s atmosphere; credit: Danish National Space Center….

7. EXPLORER 1
Once in orbit, the cosmic ray equipment of Explorer-I indicated a much lower cosmic ray count than had been anticipated. Dr. Van Allen theorized that the equipment may have been saturated by very strong radiation caused by the existence of a belt of charged particles trapped in space by the earth's magnetic field. The existence of these Van Allen Belts, discovered by Explorer-I, was confirmed by Explorer-III, which was launched on
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8. EXPLORER 1
Radiation belts are regions of high-energy particles, mainly protons and electrons, held captive by the magnetic influence of the Earth. They have two main sources. The Van Allen Belt (or inner belt) is small but very intense and trapped within 4000 miles or so of the Earth's surface. It consists mainly a high-energy protons (10-50 MeV) and is a by-product of the cosmic radiation, a thin drizzle of very fast protons and other nuclei which apparently fill all our galaxy.
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9. EXPLORER 1
REF: This composite image shows Cassiopeia A at many different wavelengths: radio polarization in red (VLA), X-rays in green (CHANDRA) and optical in blue (HST). Notice the outer shock, visible only in X-rays, as the thin green rim most visible at the top of the image. Also notice the bright ring which is visible at all three wavelengths, and the many different filamentary structures seen at each wavelength. The compact remains of the exploded star are visible only in X-rays, as the bright green spot slightly below and to the left of the geometric center of the bright ring.
Image: As above; p.8 of 19 in powerpoint presentation.
Cassiopeia A composite: Chandra (X-ray - green), VLA (radio - red) and Hubble Space Telescope (optical - blue)…2005
Explorer 1 led the way for on-going discoveries on cosmic radiation that continues today both near Earth and in galaxies.