page_title: Explorers Program
section_title: Continuation of the Explorers program
hierarchical_section_title: Explorers Program / History / Continuation of the Explorers program
caption_attribution_description: English: First-light image from the Swift Gamma-Ray Burst Mission's UVOT instrument, of the M101 "Pinwheel" Galaxy. This UVOT image combines both ultraviolet and visible light from a number of filters. Each filter is sensitive to light of a different color, ranging from ultraviolet light beyond the range of human eyesight through the blue to yellow portion of the visible spectrum. This is a 'false-color' image with the shortest wavelength ultraviolet rays being represented as blue, and the longest visible light wavelengths as red. The image shows that hot young stars are being formed in abundance in M101, especially in the spiral arms of the galaxy, where they show up in ultraviolet light. The central regions of the galaxy have more cool, old stars, which appear 'red' in the picture. A number of foreground stars, located in our own Galaxy, also reveal themselves by their red color.
context_page_description: The Explorers Program is a United States space exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was USA's first spacecraft to achieve orbit. Over
  90 space missions have been launched since. Starting with Explorer 6, it has been operated by NASA, with regular collaboration with a variety of other institutions, including many international partners.
  Launchers for the Explorers Program have included Jupiter C, Juno II, various Thor, Scout, Delta and Pegasus rockets, and Falcon 9.
  Currently, the program has three classes: Medium-Class Explorers, Small Explorers, and University-Class Explorers, with select Missions of Opportunity operated with other agencies.
context_section_description: With the establishment of NASA in 1958, the Explorers Program was transferred to NASA from the US Army. 
  NASA continued to use the name for an ongoing series of relatively small space missions, typically an artificial satellite with a specific science focus. Explorer 6 in 1959 was the first scientific satellite under the project direction of NASA's Goddard Space Flight Center.
  The Interplanetary Monitoring Platform (IMP) was launched in 1963, and involved a network of eleven Explorer satellites designed to collect data on space radiation in support of the Apollo program. The IMP program was a major step forward in spacecraft electronics design, as it was the first space program to use integrated circuit (IC) chips and MOSFETs (MOS transistors). The IMP A (Explorer 18) in 1963 was the first spacecraft to use IC chips, and the IMP D (Explorer 33) in 1966 was the first to use MOSFETs.
  Over the following two decades, NASA has launched over 50 Explorer missions, some in conjunction to military programs, usually of an exploratory or survey nature or had specific objectives not requiring the capabilities of a major space observatory. Explorer satellites have made many important discoveries on: Earth's magnetosphere and the shape of its gravity field; the solar wind; properties of micrometeoroids raining down on the Earth; ultraviolet, cosmic and X-rays from the Solar System and beyond; ionospheric physics; Solar plasma; solar energetic particles; and atmospheric physics. These missions have also investigated air density, radio astronomy, geodesy, and gamma-ray astronomy.
  With drops in NASA's budget, Explorer missions became infrequent in the early 1980s.
caption: This artificially colored view of M101 maps ultraviolet light as blue while visible light is red since UV light does not have a "color" (the eye stopping at about violet). This view was taken by the Explorer SWIFT, which can also detect X-Rays, and has contributed to the study of Gamma-ray bursts and other topics
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