Editing Explorer 7 (section)

=== Thermal Radiation ===
The Explorer 7 thermal radiation experiment was designed to measure incident and reflected solar [[Ultraviolet|UV radiation]] and terrestrial [[Infrared|IR radiation]] in order to obtain a better understanding of the driving forces of the Earth-atmosphere system. The primary instrumentation consisted of five bolometers in the form of hollow [[silver]] hemispheres that were thermally insulated from, but in close proximity to specially [[Aluminium|aluminized mirrors]]. The hemispheres thereby behaved very much like isolated spheres in space. Two of the hemispheres had black coatings and responded about equally to solar and terrestrial radiation. A third hemisphere, coated white, was more sensitive to terrestrial radiation than to solar radiation. A fourth, which had a [[Gold|gold metal surface]], was more sensitive to solar radiation than to terrestrial radiation. The fifth hemisphere, protected from direct sunlight, was used to measure the reflected sunlight. A glass-coated bead thermistor was mounted on the top of each hemisphere to measure the temperature. A complete set of four temperature observations and one reference sample required 30 seconds. Thus, in each orbit, about 180 temperature measurements could be obtained. The experiment was a success, and usable data were obtained from launch until 28 February 1961.<ref name="Instrument1">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1959-009A-01 |title=Experiment: Thermal Radiation|publisher=NASA|date=28 October 2021|access-date=2 November 2021}} {{PD-notice}}</ref>

Significantly, it also carried [[Verner Suomi|Dr. Verner E. Suomi]]'s flat-plate [[radiometer]], improved with the help of [[Bob Parent (professor)|Robert Parent]], that took the first [[Earth radiation budget]] measurements from space and initiated the era of [[satellite]] studies of the [[climate]]. It made the [[first images of Earth from space|first coarse maps]] of "the solar radiation reflected by the Earth and the infrared radiation emitted by the Earth".<ref name="Kidder Vonder Haar 1995 p. 2">{{cite book|last1=Kidder|first1=S. Q.|last2=Vonder Haar|first2=T. H.|title=Satellite Meteorology: An Introduction
|publisher=Elsevier Science|isbn=978-0-08-057200-0|page=2|year=1995|url=https://books.google.com/books?id=M5dsBgAAQBAJ|access-date=2020-10-05}}</ref>

Using both satellite observations of the Earth's heat balance and [[atmosphere|atmospheric]] cooling rates measured by net flux radiosondes, Suomi established the important role played by [[cloud]]s in absorbing radiated [[solar energy]]. These observations established that Earth's energy budget varies markedly due to the effect of clouds, the surface albedo, and other absorbing constituents. Using these instruments, Suomi and his team discovered that the [[Earth]] absorbed more of the [[Sun]]'s energy than originally thought and demonstrated that it was possible to measure and quantify seasonal changes in the global heat budget. Explorer 7 was unable to detect solar X-rays due to its sensors being saturated by background radiation in the [[Van Allen radiation belt]].<ref name=SP100>{{cite book|date=1966 |title=Significant Achievements in Solar Physics 1958-1964|page=63|location=Washington D.C.|publisher=NASA}} {{PD-notice}}</ref>