Editing Explorer 7 (section)

== Experiments ==
=== Ground Based Ionospheric ===
An all-transistor beacon telemetry transmitter was operated at a fundamental frequency of 19.9915 [[Hertz|MHz]]. This transmitter, which was powered by solar cells and rechargeable nickel-cadmium batteries, provided 660-mW of power at the fundamental frequency. It also radiated the second and third harmonics (15-mW each) at 39.9830 and 59.9745-MHz. Beacon receivers were known to have been located in [[Washington, D.C.]], and [[Chicago]], [[Illinois]]. Interpretation of the changes of beacon signal characteristics between the satellite and the ground station showed irregularities to be present at all times of the day with horizontal dimensions of {{cvt|5|km}} to {{cvt|500|km}}. Data were received over a period of 16 months.<ref name="Instrument6">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1959-009A-06|title=Experiment: Ground Based Ionospheric|publisher=NASA|date=28 October 2021|access-date=2 November 2021}} {{PD-notice}}</ref>

=== Heavy Primary Cosmic Rays ===
This experiment was designed to measure the omnidirectional flux of heavy primary cosmic rays in the rigidity range 1 to 15.5 [[Volt|GV]]. Particles with atomic numbers Z >5, Z >8, and Z >15 were counted separately by an ionization chamber in which each incident particle yielded a pulse. Pulse amplitude was substantially independent of the energy of the incident particle but was proportional to the square of its Z value. Each of the three counting rates was determined every 15 seconds. The experiment performed as planned from launch until 25 October 1959. About 80% of the data acquired for the 25 October 1959, to 31 May 1960, period are useful, with most problems occurring in the lowest Z mode. Very little useful data were acquired after 31 May 1960.<ref name="Instrument3">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1959-009A-03|title=Experiment: Heavy Primary Cosmic Rays|publisher=NASA|date=28 October 2021|access-date=2 November 2021}} {{PD-notice}}</ref>

=== Micrometeorite ===
Three photoconducting [[cadmium sulfide]] cells were used to measure [[micrometeorite]] penetration and molecular sputtering. The three cells were identical in design and effective area (18 sq mm) and were mounted on a [[magnesium]] plate on the satellite's equator facing outward perpendicular to the satellite's spin axis. The experiment was exposed to the space environment of micrometeorites, trapped radiation, and sputtering for 38 days of active life. The three cells and a thermistor that was included as part of the experiment performed normally. One cell was penetrated on the 16th day by a particle approximately 10 microns in diameter.<ref name="Instrument5">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1959-009A-05|title=Experiment: Micrometeorite|publisher=NASA|date=28 October 2021|access-date=2 November 2021}} {{PD-notice}}</ref>

=== Solar X-Ray and Lyman-Alpha Radiation ===
The solar X-ray and Lyman-alpha radiation were measured by means of gas ionization chambers mounted on opposite sides of the upper portion of the double cone configuration of the Explorer 7 satellite. Intensities were monitored in order to obtain a long-term history of solar X-ray and [[Lyman-alpha emitter|Lyman-alpha]] fluxes and to correlate these with terrestrial atmospheric responses. The two X-ray detectors ({{cvt|2.5|cm}} deep) were filled with argon gas and had beryllium windows (.021 g/sq cm) resulting in a sensitivity to X-rays in the 2 to 8 [[Angstrom|A]] range. The Lyman-alpha detectors (on the opposite side), which were circular ionization chambers ({{cvt|1.9|cm}} in diameter) filled with [[Nitric oxide|nitric oxide gas]], had [[lithium fluoride]] windows. Their sensitivity was in the 1050 to 1350 A interval. The data, however, were impossible to interpret in terms of incident solar radiation due to both the saturation of detector circuits by Van Allen radiation (150 keV [[electron]]s) and electronic difficulties in the feedback amplifier.<ref name="Instrument2">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1959-009A-02|title=Experiment: Solar X-Ray and Lyman-Alpha Radiation |publisher=NASA|date=28 October 2021|access-date=2 November 2021}} {{PD-notice}}</ref>

=== 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>

=== Trapped Radiation and Solar Protons ===
Two omnidirectional [[Geiger counter]]s (Anton 302 and 112) were used to conduct a comprehensive spatial and temporal monitoring of total cosmic-ray intensity, geomagnetically trapped corpuscular radiation, and [[Solar particle event|solar protons]]. The detector was sensitive to protons (E >20 MeV) and electrons (E >30 keV). The experiment operated satisfactorily from launch until 28 February 1961, except for a brief period in September and October 1960.<ref name="Instrument4">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1959-009A-04|title=Experiment: Trapped Radiation and Solar Protons|publisher=NASA |date=28 October 2021|access-date=2 November 2021}} {{PD-notice}}</ref>