Delta J
The Delta J, or Thor-Delta J was an American expendable launch system of the late 1960s. Only one was launched, with the Explorer 38 spacecraft. It was a member of the Delta family of rockets. The Delta J was derived from the Delta E. The first stage was a Thor missile in the DSV-2C configuration, with three Castor-1 solid rocket boosters clustered around it. A Delta E was used as the second stage. The Altair third stage of the Delta E was replaced with the more powerful Star 37D SRM. The only Delta J to fly was launched from Vandenberg Air Force Base Space Launch Complex 2E on 4 July 1968. It successfully placed the Explorer 38 satellite into medium Earth orbit A medium Earth orbit (MEO) is an geocentric orbit, Earth-centered orbit with an altitude above a low Earth orbit (LEO) and below a high Earth orbit (HEO) – between above sea level.

Explorer 38
Explorer 38 (also called as Radio Astronomy Explorer A, RAE-A and RAE-1) was the first NASA satellite to study Radio astronomy. Explorer 38 was launched as part of the Explorer program, being the first of the 2 RAE-satellites. Explorer 38 was launched on 4 July 1968 from Vandenberg Air Force Base, California, with a Delta J launch vehicle. Spacecraft Explorer 38 spacecraft measured the intensity of celestial radio sources, particularly the Sun, as a function of time, direction and frequency (0.2 to 20-MHz). The spacecraft was gravity-gradient stabilized. The spacecraft weight was , and average power consumption was 25 watts. It carried two long V-antennas, one facing toward the Earth and one facing away from the Earth. A long dipole antenna was oriented tangentially with respect to the Earth's surface. The spacecraft was also equipped with one 136-MHz telemetry turnstile. The onboard experiments consisted of four step-frequency Ryle-Vonberg radiometers operating from 0. ...
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