Editing Mariner 1 (section)

===Scientific package===
[[File:Mariner 1 in JPL's Spacecraft Assembly Facility.jpg|thumb|Mariner 1 in JPL's Spacecraft Assembly Facility]]

====Background====

At the time of the Mariner project's inception, few of Venus' characteristics were definitely known. Its opaque [[atmosphere of Venus|atmosphere]] precluded [[telescope|telescopic]] study of the ground. It was unknown whether there was water beneath the clouds, though a small amount of [[water vapor]] above them had been detected. The planet's [[rotation rate]] was uncertain, though JPL scientists had concluded through [[radar]] observation that Venus rotated very slowly compared to the Earth, advancing the long-standing<ref name=beyond1/> (but eventually disproven)<ref name=nasa1/> hypothesis that the planet was [[Tidal locking|tidally locked]] with respect to the Sun (as the Moon is with respect to the Earth).<ref name=avweek1961/> No oxygen had been detected in Venus' atmosphere, suggesting that life as existed on Earth was not present. It had been determined that Venus' atmosphere contained at least 500 times as much [[carbon dioxide]] as the Earth's. These comparatively high levels suggested that the planet might be subject to a [[runaway greenhouse effect]] with surface temperatures as high as {{cvt|600|K}}, but this had not yet been conclusively determined.<ref name=report/>{{rp|7–8}}

The Mariner spacecraft would be able to verify this hypothesis by measuring the temperature of Venus close-up;<ref name=avweek1960a/> at the same time, the spacecraft could determine if there was a significant disparity between night and daytime temperatures.<ref name=report/>{{rp|331}} An on-board [[magnetometer]] and suite of charged particle detectors could determine if Venus possessed an appreciable magnetic field and an analog to Earth's [[Van Allen Belts]].<ref name=avweek1960a/>

As the Mariner spacecraft would spend most of its journey to Venus in interplanetary space, the mission also offered an opportunity for long-term measurement of the [[solar wind]] of charged particles and to map the variations in the Sun's [[magnetosphere]]. The concentration of [[cosmic dust]] beyond the vicinity of Earth could be explored as well.<ref name=treasury/>{{rp|176}}

====Experiments====

Experiments for the measurement of Venus and interplanetary space included:

*A [[Microphone#Piezoelectric microphone|crystal microphone]] for measurement of the density of cosmic dust, mounted on the central frame.
*A [[proton]] detector for counting low-energy protons in the solar wind, also mounted on the central frame.
*Two [[Geiger–Müller tube|Geiger-Müller (GM) tubes]] and an [[ion chamber]], for measuring high-energy charged particles in interplanetary space and in the Venusian equivalent of Earth's Van Allen Belts (which were later shown not to exist). These were mounted on Mariner's long axis to avoid the magnetic fields of the control equipment as well as secondary radiation caused by [[cosmic rays]] hitting the metal structure of the spacecraft. 
*An Anton special-purpose GM tube, for measuring lower energy radiation, particularly near Venus, also mounted away from the central frame.
*A three-axis [[Spacecraft magnetometer#Fluxgate magnetometers|fluxgate magnetometer]]<ref name=NSSDC/> for measuring the Sun's and Venus' magnetic fields, also mounted away from the central frame.
*A microwave [[radiometer]], a {{cvt|20|in}} diameter, {{cvt|3|in}} deep, parabolic antenna designed to scan Venus up and down at two microwave wavelengths (19&nbsp;mm and 13.5mm), slowing down and reversing when it found a hot spot. The 19&nbsp;mm wavelength was for measuring the temperature of the planet's surface while the 13.5mm wavelength measured the temperature of Venus' cloudtops. The instrument was mounted just above the central frame.
*Two [[infrared]] optical sensors for parallel measurement of the temperature of Venus, one at 8 to 9 [[microns]], the other at 10-10.8 microns, also mounted above the central frame.{{r|treasury|report}}{{rp|9}}<ref name=avweek1960a/>

Not included on any of the Mariner R spacecraft was a camera for visual photos. With payload space at a premium, project scientists considered a camera an unneeded luxury, unable to return useful scientific results. [[Carl Sagan]], one of the Mariner R scientists, unsuccessfully fought for their inclusion, noting that not only might there be breaks in Venus' cloud layer, but "that cameras could also answer questions that we were way too dumb to even pose".<ref name=space.com1/>