The Injun program was a series of six satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s designed and built by researchers at the University of Iowa

University of Iowa

The University of Iowa is a public state-supported research university located in Iowa City, Iowa, United States. It is the oldest public university in the state. The university is organized into eleven colleges granting undergraduate, graduate, and professional degrees...

. They were intended to observe various radiation and magnetic phenomena in the ionosphere

Ionosphere

The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

 and beyond.

The design specifics of the satellites had little in common, though all were solar-powered and the first five used magnetic stabilization to control spacecraft attitude. (The last in the series was spin-stabilized.) Instruments included particle detectors of varying types, magnetometer

Magnetometer

A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...

s, and photometer

Photometer

In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...

s for observing aurora

Aurora (astronomy)

An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...

s. The last three satellites were launched as part of the Explorer program

Explorer program

The Explorer program is a United States space exploration program that provides flight opportunities for physics, heliophysics, and astrophysics investigations from space. Over 90 space missions have been launched from 1958 to 2011, and it is still active...

.

In spite of various hardware difficulties and the loss of Injun 2 due to an upper stage failure, the program was generally successful. In particular they produced data on the radiation aftereffects of the Starfish Prime

Starfish Prime

Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the Atomic Energy Commission and the Defense Atomic Support Agency ....

 high-altitude nuclear test

High altitude nuclear explosion

High-altitude nuclear explosions have historically been nuclear explosions which take place above altitudes of 30 km, still inside the Earth's atmosphere. Such explosions have been tests of nuclear weapons, used to determine the effects of the blast and radiation in the exoatmospheric...

.

Program details

Name	Also known as	Launched	Vehicle	Ceased operation	Notes
Injun 1		June 29, 1961	Thor-Able Thor-Able The Thor-Able was an American expendable launch system and sounding rocket used for a series of re-entry vehicle tests and satellite launches between 1958 and 1960. It was a two stage rocket, consisting of a Thor IRBM as a first stage, and a Vanguard-derived Able second stage. On some flights, an...	March 6, 1963	Failed to separate from Solrad 3; still in orbit
Injun 2		January 24, 1962	Thor-Able Thor-Able The Thor-Able was an American expendable launch system and sounding rocket used for a series of re-entry vehicle tests and satellite launches between 1958 and 1960. It was a two stage rocket, consisting of a Thor IRBM as a first stage, and a Vanguard-derived Able second stage. On some flights, an...	failed at launch	Upper stage produced insufficient thrust
Injun 3		December 12, 1962	Thor-Agena Thor-Agena Thor-Agena was a series of orbital launch vehicles. The rockets used Thor first stages and Agena second stages. They are thus cousins of the more famous Thor-Deltas, which founded the Delta rocket family. The first attempted launch of a Thor-Agena was in January 1959...	August 25, 1968
Injun 4	IE B, Explorer 25	November 21, 1964	Scout X-4 Scout (rocket) The Scout family of rockets were launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first orbital launch vehicle to be entirely composed of solid fuel stages....	December 1966	still in orbit
Injun 5	IE C, Explorer 40	August 8, 1968	Scout X-4 Scout (rocket) The Scout family of rockets were launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first orbital launch vehicle to be entirely composed of solid fuel stages....	June 1971	still in orbit
Injun 6	IE D, Hawkeye, Explorer 52 Explorer 52 Explorer 52 was a US satellite launched on June 3, 1974 from Vandenberg Air Force Base on a Scout booster.This satellite was also known as:* Hawkeye 1* IE D* Injun 6* Injun F* Neutral Point Explorer* 07325... , Neutral Point Explorer	June 3, 1974	Scout X-4 Scout (rocket) The Scout family of rockets were launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first orbital launch vehicle to be entirely composed of solid fuel stages....	April 28, 1978	main article: Explorer 52 Explorer 52 Explorer 52 was a US satellite launched on June 3, 1974 from Vandenberg Air Force Base on a Scout booster.This satellite was also known as:* Hawkeye 1* IE D* Injun 6* Injun F* Neutral Point Explorer* 07325...