Editing Explorer 1 (section)

== Spacecraft ==
[[File:Explorer1 preparations.jpg|thumb|upright=1.0|left|The satellite Explorer 1 is mated to its booster at LC-26.]]

Explorer 1 was designed and built by [[California Institute of Technology]]'s JPL under the direction of Dr. [[William Hayward Pickering]]. It was the second satellite to carry a mission payload (Sputnik 2 was the first).

The total mass of the satellite was {{cvt|13.97|kg}}, of which {{cvt|8.3|kg}} were instrumentation. In comparison, the mass of the first Soviet satellite Sputnik 1 was {{cvt|83.6|kg}}. The instrument section at the front end of the satellite and the empty scaled-down fourth-stage rocket casing orbited as a single unit, spinning around its long axis at 750 revolutions per minute.

Data from the scientific instruments was transmitted to the ground by two antennas. A 60 [[Watt|milliwatt]] transmitter fed a [[dipole antenna]] consisting of two fiberglasses [[slot antenna]]s in the body of the satellite operating on 108.03 [[Hertz|MHz]], and four flexible whips forming a [[turnstile antenna]] were fed by a 10 milliwatt transmitter operating on 108.00 MHz.<ref name="data sheet"/><ref name="Williams">{{cite journal |last=Williams |first=W. E. Jr. |date=April 1960 |title=Space Telemetry Systems |url=https://ieeexplore.ieee.org/document/4066076 |journal=Proceedings of the Institute of Radio Engineers |volume=48 |issue=4 |pages=685–690 |doi=10.1109/JRPROC.1960.287448 |s2cid=51646193 |access-date=30 July 2024|url-access=subscription }}</ref>

Because of the limited space available and the requirements for low weight, the payload instrumentation was designed and built with simplicity and high reliability in mind, using [[germanium]] and [[silicon]] transistors in its electronics.<ref name="semiconductormuseum">{{cite web |url=http://semiconductormuseum.com/Transistors/LectureHall/Ludwig/Ludwig_Index.htm |title=The First Transistors in Space – Personal Reflections by the Designer of the Cosmic Ray Instrumentation Package for the Explorer I Satellite |access-date=2008-02-25 |work=A Transistor Museum Interview with Dr. George Ludwig |publisher=The Transistor Museum}}</ref> A total of 20 transistors were used in Explorer 1, plus additional ones in the Army's micrometeorite amplifier. Electrical power was provided by [[Mercury battery|mercury chemical batteries]] that made up approximately 40% of the payload weight.

The external skin of the instrument section was sandblasted [[stainless steel]] with white stripes. Several other color schemes had been tested, resulting in backup articles, models, and photographs showing different configurations, including alternate white and green striping and blue stripes alternating with copper. The final color scheme was determined by studies of shadow–sunlight intervals based on firing time, trajectory, orbit and inclination.

[[File:Explorer1 sketch.jpg|thumb|upright=1.0|left|''Explorer 1 schematic'']]